Servo Magazine 02-2017

Cutting Corners, Without Compromise! Compact convenience and economic efficiency are the hallmarks of our new RDX1 charger. Its space-saving, affordable design fits every workbench and budget. This potent AC/DC charger features a backlit 3.2-inch LCD screen and accessible front panel ports for easy charging of all your batteries. Integrated balancing, microprocessor-control, USB functionality and a PC interface combine to make the RDX1 the obvious solution to your charging needs. FEATURES: • Optimized Operating Software • 10 Battery Memory • Internal Lithium Battery Balancer • Multiple Lithium Battery Charge Modes • Works with Hitec’s “Charge Master” Software • LiPo Battery Meter SPECIFICATIONS: • AC Input Voltage: 100-240V • DC Input: 11-18V • Charge Power: 60W • Charge Current Range: 0.1 - 6.0A • Max. Discharge Power: 5W • Discharge Current Range: 0.1 - 2.0A • Balancing Port Current Drain: 200MA/Cell Hitec RCD USA, Inc. / 12115 Paine St. Poway, CA 92064 / 858.748.6948 / www.hitecrcd.com /

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02.2017 VOL. 15 NO. 2 Subscription Information SERVO Magazine — PO Box 15277 North Hollywood, CA 91615-9218 Call 877-525-2539 or go to www.servomagazine.com Subscribe • Gift • Renewal • Change of Info

Columns 08 Robytes

60 Then and Now

by Jeff and Jenn Eckert

by Tom Carroll

Stimulating Robot Tidbits • Fish-Zapping ROV • Astrobot Comes to Earth • Bye-Bye Selfie Sticks • Geriatric Puppy Bot

Building a Robot? Just Go for It! Constructing your own automaton doesn’t require a bunch of fancy equipment or expensive tools. If you have a basic mechanical aptitude and the desire to learn, you’re already more than halfway there!

10 Ask Mr. Roboto with Eric Ostendorff

Topics discussed this time include servo options, dealing with a sonar range finder’s erratic responses, an explanation for jittery servos, and to LEGO or not to LEGO.

54 Twin Tweaks by Bryce and Evan Woolley

Junkyard Warrior Building cool stuff out of junk you have laying around has a proud and colorful history. We will continue that tradition for our project this month by only scavenging stuff from our garage and self-imposing a time limit. PAGE 60

The Combat Zone 18 BUILD REPORT: My First Antweight — A Dark and Dirty Disco 21 An Interview with Ed McCarron 24 EVENT REPORT: Pennsylvania College of Technology SWORD Fights 26 EVENT REPORT: Robot Battles 61 at the Geek Media Expo

Departments

16 Bots in Brief • Working on the ChainFORM Gang • PABI Offers Cost-Effective Therapy Solution • Self-Balancing GyroCycle Soon to Hit the Big Slab

06 Mind/Iron

Underwater Remotely Operated Vehicles: The Next Big Thing in Robotics?

14 New Products 15 Events Calendar

39 47 65 66

RoboLinks Showcase Advertiser’s Index SERVO Webstore

SERVO Magazine (ISSN 1546-0592/CDN Pub Agree#40702530) is published monthly for $26.95 per year by T & L Publications, Inc., 430 Princeland Court, Corona, CA 92879. PERIODICALS POSTAGE PAID AT CORONA, CA AND AT ADDITIONAL ENTRY MAILING OFFICES. POSTMASTER: Send address changes to SERVO Magazine, P.O. Box 15277, North Hollywood, CA 91615 or Station A, P.O. Box 54, Windsor ON N9A 6J5; [email protected]

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In This Issue ... 30 Animatronics for the Do-It-Yourselfer by Steve Koci Servos: The Basics and Beyond Becoming comfortable using servos and taking advantage of all the added features available will expand your capabilities as a builder. Let's take a look at why they are so special.

PAGE 36

36 Serving Raspberry Pi — Giving Berry a Better Servo Mount by William Henning In the last article, the accuracy of the heading produced by our Raspberry Pi bot, Berry's compass was greatly improved by adding magnetic declination and tilt compensation. However, that by itself is not enough for indoor navigation. I’ll need a few more upgrades first. However, Berry's head keeps falling off. Time for a better mount!

40 Building the KReduCNC by Michael Simpson It’s been a while since we started this project, so let’s go over spindle hookup and get ready to make something.

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44 Get Social with FaceBox: the Friendly HeadBot by Dave Prochnow If you weren’t lucky enough to score one of SparkFun Electronics’ limited edition Cyber Monday Redbox Robots, then you’re in luck! We’ve come up with our own version that is a tracking, flashing, and speaking robot.

48 The Multi-Rotor Hobbyist by John Leeman Fat Shark Teleporter V5 Review As multi-rotor pilots, we can now have a first person view (FPV) experience with inexpensive/all-in-on equipment that literally puts us in the pilot’s seat and immerses us in the experience of flying.

13 MaxRoboTech Comics Autonomous Robotics and Control

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Mind / Iron by Bryan Bergeron, Editor ª

Underwater Remotely Operated Vehicles: The Next Big Thing in Robotics? ’ve built and flown several quadcopters, including a fiberglass and carbon fiber unit with 4 kg of onboard lithium-ion batteries. However, because the nearest park is almost always occupied, my go-to quadcopter is a palm-sized unit that I fly indoors. In my controlled environment, I don’t have to worry about my 6 oz drone falling from the sky onto a pedestrian, dog, or automobile. However, it just isn’t as exciting as flying outside with multiple environmental factors to deal with, from trees and birds to blowing leaves. While it’s a given that flying drones in some form is here to stay, there’s clearly an unmet need for robotics enthusiasts who want to break out of their bedrooms. Enter Underwater Remotely Operated Vehicles (UROVs) — the little brothers to the massive commercial underwater vehicles used to inspect hulls, ship wrecks, and pipe lines. In terms of commercial availability, UROVs — sometimes referred to as Robosubs — are where quadcopters were five years ago. As such, you’re not going to find a UROV hanging in a bubble pack next to the $39 quadcopters at RadioShack. Parts are relatively expensive, and you’ll likely have to fabricate a few things from scratch — all great challenges for an experimenter. I’ve only built one UROV — a bare bones model that survived several excursions in a nearby pond. Although it might seem counterintuitive, a typical quadcopter is much simpler to design, build, and operate. Aside from locating affordable parts, the challenges in building a UROV (in order of importance) are keeping the electronics dry, power, and heat dissipation. Starting with the affordable parts issue, I made my first underwater drone with four used 12V trolling motors that I found on eBay for about $50/motor. A 12” length of 8” diameter PVC pipe with threaded end caps served as the main chassis. This wasn’t the safest design because the props were exposed. Another limitation is that all four motors were designed for right handed rotation. As with quadcopters, you’ll want to use both left and right handed motors. Camera selection was a no-brainer — I simply mounted my GoPro on the PVC pipe using an elastic strap to avoid drilling additional holes in the pipe. For an example of parts designed specifically for UROV use, check out the CrustCrawler site (www.crust crawler.com) — my go-to source for aluminum robot arms and crawlers. CrustCrawler sells 400W and 600W thrusters, with fully enclosed props, excellent mounting brackets, and waterproof connectors. They also sell transparent waterproof enclosures that can hold lights, a camera, and an Arduino or other controller. At nearly $1K for a 600W thruster, however, these top-end parts are clearly best suited for a robotics club with multiple members sharing the cost. The challenge of keeping critical components dry is best met by using marine connectors designed for this purpose, as well as using grease on the rubber seals leading to and from the main electronics housing. Obviously, you’ll have to use motors designed for full immersion. Power is in some ways less of an issue than with quadcopters. Instead of dealing with lithium-ion batteries and chargers, you’ll likely use one or two car batteries or an AC powered supply connected to the UROV via an umbilical cord. The cord is a bother in that it limits both maneuverability and maximum

I

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FOR THE ROBOT INNOVATOR

ERVO

Published Monthly By T & L Publications, Inc. 430 Princeland Ct., Corona, CA 92879-1300 (951) 371-8497 FAX (951) 371-3052 Webstore Only 1-800-783-4624 www.servomagazine.com Subscriptions Toll Free 1-877-525-2539 Outside US 1-818-487-4545 P.O. Box 15277, N. Hollywood, CA 91615 PUBLISHER Larry Lemieux [email protected] ASSOCIATE PUBLISHER/ ADVERTISING SALES Robin Lemieux [email protected] EDITOR Bryan Bergeron [email protected] VP of OPERATIONS Vern Graner [email protected] CONTRIBUTING EDITORS Tom Carroll Kevin Berry R. Steven Rainwater Michael Simpson Steve Koci John Leeman Eric Ostendorff Dave Prochnow Jeff Eckert Jenn Eckert Bryce Woolley Evan Woolley William Henning Ricky Matsko Brandon Davis Nate Franklin Thomas Kenney CIRCULATION DEPARTMENT [email protected] WEBSTORE MARKETING COVER GRAPHICS Brian Kirkpatrick [email protected] WEBSTORE MANAGER/ PRODUCTION Sean Lemieux [email protected] ADMINISTRATIVE STAFF Re Gandara Copyright 2017 by T & L Publications, Inc. All Rights Reserved

All advertising is subject to publisher’s approval. We are not responsible for mistakes, misprints, or typographical errors. SERVO Magazine assumes no responsibility for the availability or condition of advertised items or for the honesty of the advertiser. The publisher makes no claims for the legality of any item advertised in SERVO. This is the sole responsibility of the advertiser. Advertisers and their agencies agree to indemnify and protect the publisher from any and all claims, action, or expense arising from advertising placed in SERVO. Please send all editorial correspondence, UPS, overnight mail, and artwork to: 430 Princeland Court, Corona, CA 92879.

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range. However, if you have access to a 110 VAC operated power supply, excursion time is virtually unlimited — even with high-drain flood lights. Heat dissipation and thermal failure can be a problem on extended excursions if you stuff all of the control circuitry in a small airtight chamber with no thermal sink to the water. One option is to use a metal chassis that is at least partially exposed to the water. Another is to use an airtight chamber with ample free space surrounding the heat-generating components. Of course, these are just highlights of the current state of UROVs. For more information, check out the Marine Advanced Technology Education (MATE) website for information on international UROV competitions held every summer at the NASA Johnston Space Center’s Neutral Buoyancy Lab. With time, prices will drop, parts will become more plentiful, and the Web will be full of videos of underwater sea life and perhaps even battling UROVs. SV

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Robytes by Jeff and Jenn Eckert Fish-Zapping ROV In case you haven’t heard, we have a serious problem with lionfish. As summarized by the World Lionfish Hunters Association (lionfish.co), “Invasive lionfish are disastrously out-breeding, out-living, out-eating, and out-competing every other native fish in the Western Atlantic Ocean, Gulf of Mexico, and the Caribbean Sea. If left unchecked, lionfish will ultimately cause the destruction of the reefs, native fish stocks, and the livelihoods of everyone that depends on them.” A suggested solution is that we catch and eat more of them, and lionfish are said to be tasty. Problem is, they are equipped with venomous spines that dampen most people’s desire to fish for them, and given that a female can release up to two million eggs per year, it would take a lot of fishing to make a dent in the population. To combat the problem, more than a dozen partners — including iRobot, electrofisher builder Smith-Root, ocean exploration organization Nekton, and various Bermudan institutions — have joined together to form Robots in Service of the Environment (RISE, robotsise.com). Their solution is the Harvester lionfish hunter which is currently just a prototype, and is sort of a combination bug zapper

Astrobot Comes to Earth

Prototype of RISE’s lionfish hunter robot.

and underwater Roomba. (There is also a version armed with a spear.) Zapped fish are to be collected in a central chamber and harvested for food. RISE plans to eventually launch thousands of units so — with any luck — filets will eventually be showing up on the menu in your local seafood hangout. When that happens, we all need to do our ecological duty and eat up!

conversation while moving its head and hands. Conversations You may recall Kirobo, a robocan even include information that astronaut that hung around the the little guy collects via Bluetooth International Space Station for 18 in your home or car. Presumably, months starting in August 2013. this will allow it to say things like Kirobo was created by the “be careful” when you’re about to University of Tokyo and roboticist drive into a tree or “open Tomotaka Takahashi (with containers are illegal” when you assistance from Toyota and the pop a can of beer. Japan Aerospace Exploration The built-in camera enables it Agency), specifically to assist to recognize people’s facial Commander Koichi Wakata, the expressions, detect their emotional first Japanese ISS commander. state, and react accordingly. Using some of the same However, the Mini doesn’t include technology, Toyota has announced face recognition, so it won’t know the upcoming availability of its Aunt Akira from Uncle Takumi. Kirobo Mini robot. The Mini — There’s bad news if you want one, only 10 cm (4 in) tall when sitting though. — is a miniature communication The initial version will only be Toyota’s Kirobo Mini companion bot. partner developed solely “to sold in Japan, and it only speaks provide companionship” and be a “cuddly companion.” Japanese, so if you currently are in need of a friend, well, Kirobo Mini doesn’t actually do much, but it can turn forget it. One will cost about $400 at current exchange its head toward the person speaking and engage in casual rates, so it’s probably just as well.

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Go to www.servomagazine.com/index.php/magazine/article/February2017_Robytes to comment on these topics.

Bye-Bye Selfie Sticks For those who are so deeply into self-documentation that a simple selfie stick just doesn’t do it anymore, Zero Zero Robotics (gethover.com) has unveiled its first product: the Hover Camera, launched with $25 million in funding from various investors. Based on the Qualcomm Snapdragon Flight drone platform, the camera uses embedded AI to intelligently navigate and avoid obstacles while snapping 13 MP photos or capturing 4K video of whatever events you think will fascinate the rest of the world. The camera tracks your face and body to keep you in the picture, and proprietary technology digitally stabilizes photos and video by eliminating shakes and jitters. Operation is about as simple as it could be: You just toss the camera away from you, and it automatically rights itself and hovers nearby. It also features steady hovering via a 3 MP downward-facing camera and the ability to capture 360° panoramic images. It is notable that, at only 238 g (8.4 oz), it squeaks in under the FAA 250 g Hobbyist Drone Registration weight limit, so you can thumb your nose at the feds. Although the device operates independently, you can use its iOS or Android app to position it with taps and swipes, even at altitudes of up to 164 ft (50 m). Care is advised, as the batteries become drained after about seven minutes. The Hover Camera is built by Foxconn Technology

Zero Zero Robotics’ Hover Camera.

which, of course, also makes iPads and iPhones, Kindles, PlayStations, and other well known products. No official price has been announced as of this writing, but it is expected to be in the neighborhood of $600.

Geriatric Puppy Bot

Companion Pet Pup is a lifelike pet alternative. It In November 2015, looks, sounds, and feels like a toymaker Hasbro real dog; when the pup’s (www.hasbro.com) decided “owner” speaks, it looks to expand into the over-thetoward him/her and reacts hill market with its “Joy for with realistic puppy sounds.” All” Companion Cat bot. Using its built-in sensors Apparently, the ersatz kitty and speakers, the bowwow caught on quickly with both bot will nuzzle its owner’s oldsters and caregivers, as it hand, woof when it hears inspired Today’s Caregiver someone talk to it, and move magazine to award Hasbro its head when petted. If Hasbro’s Companion Pet Pup, complete with heartbeat and its 2016 Caregiver Friendly grandpa happens to nod off, lifelike fur coat. Award. it will do the same. Naturally, this generated For some unknown reason, Pet considerable grousing on the part of Pup costs more than Companion Cat dog-loving golden agers, so the ($119.99 vs. $99.99) but, on the company has now responded with its bright side, no one has to walk it, new Companion Pet Pup. and it will never chew up grandpa’s According to Hasbro, “With shoes or drink out of the toilet. It’s BarkBack™ technology and a soft available now at www.qvc.com. SV built-in heartbeat, the Joy for All

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Ask Mr. Roboto Tap into the sum of all human knowledge and get your questions answered here! From software algorithms to material selection, Mr. Roboto strives to meet you where you are — and what more would you expect from a complex service droid?

Q

. I notice that choices in servo options seem to have really grown! They now tout all kinds of specifications such as “metal gear,” “ball bearing,” “digital,” “high speed,” and the like. Do you have a rule of thumb for picking the best suited servo for a given job? For example, when it might be best to pick a servo with metal gears or when it would be best to choose a “digital” servo over a regular one?

A

Elias Smith St. Louis, MO

. Great question and such a HUGE topic. I wrote an article on analog servos in the July 2015 issue and just scratched the surface. The vast array of servos and accessories at a place like ServoCity alone is crazy. You can pore over spec sheets to compare servos, but nothing beats hands-on experience to get a feel for how much force / torque / travel / power a servo can deliver. Standard sized light-duty analog servos like Hitec’s HS-311 or Futaba’s S3003 are inexpensive baseline references. Priced at $10-$15, most have brushed DC motors, replaceable plastic/resin gears, and bushings, not bearings (Figure 1, center). They are fine for many lightweight robots. I have used them for simple walkers and light-duty robot arms where repeatability is more important than speed or power. As your requirement for power/torque grows, you will need to change to either bigger or metal gear servos. Vigor’s VS-11 (Figure 1, left) is a

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with Eric Ostendorff Our resident expert on all things robotic is merely an email away.

[email protected]

rotation, center and end points, failsafe option, Figure 1. speed, and dead bandwidth adjustment. In a robot, the microcontroller does that, coordinating servos while monitoring sensors and control input. So, digital servos may or may not be drastically better than analog for any given robotics application. If you have a fastrunning juggling humanoid robot with crazy dynamics and personal favorite of mine; it’s a very accelerations which require PID loops inexpensive 1/4 scale servo with and Kalman filters, then by all means bigger, fatter, and stronger plastic go digital. For a stately hexapod, a gears. block-stacking arm, and other lessIf you have room, it is suitable for demanding applications, old-school some heavy duty applications, as are analog servos might work just as well. most other 1/4 scale servos. Otherwise, you can use standard size . I’ve been experimenting servos with stronger gears. Metal with a sonar range finder on gears are much $tronger (!) than my robot and have noticed a plastic/resin gears for high/shock tendency for the responses to be loads, but wear faster. Hitec’s erratic depending on the target Karbonite is a reinforced plastic which surfaces (e.g., painted wall vs. claims both higher strength and less curtains). In some cases, I don’t get wear than standard plastic gears. Ball readings at all and it seems to happen bearings are useful in high-load if the target wall is at a 45 degree applications to reduce friction and angle from the sensor. Given the wear. apparently unreliable readings I’m Digital servos are faster, more getting, I would appreciate some accurate, more expensive, and more advice on how to make sure my robot power-hungry than analog servos. doesn’t run into things! Emerson Sandoval Futaba has a very helpful PDF at Maryland Heights, MO www.futabarc.com/servos/digitals ervos.pdf. They respond to the same 50 Hz control signals as analog . Therein lies the rub! Ultrasonic servos, but the internal PCB (printed sensors rely on echos circuit board) drives the motor at 300 (reflections) of emitted bursts. Hz for better control. Big flat solid perpendicular surfaces Digital servos really shine in RC reflect straight back and are easy to aircraft because they are individually sense. Cloth curtains absorb / programmable for direction of dissipate the signal, and oblique

Q

A

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Your robotic problems solved here. Post comments on this article at www.servomagazine.com/index.php/magazine/article/February2017_MrRoboto.

angled walls can reflect the echo away in a useless direction. “Sensor fusion” is the latest buzzword to network and monitor multiple sensors; often different types of sensors. Each sensor has its own strengths and weaknesses. Combining a Sharp IR distance sensor (which outputs an analog signal) with an ultrasonic sensor is increasingly popular with the robotics crowd. Parallax sells a special aluminum bracket (Figure 2) to hold a PING))) ultrasonic sensor and a Sharp sensor (https:// www.parallax .com/ product/725-28915). You can make your own simple IR sensor(s) with a 38 kHz IR receiver module and an IR LED, Figure 3. which rely purely on IR reflection. These will have a good response to white / shiny / reflective objects, but little or no response to dark / black / matte objects. The Sharp sensor has the advantage in that it uses a Position Sensitive Detector (PSD) and can detect black objects nearly as well as white. Additionally, the Sharp module is calibrated to measure distances with good accuracy. Another technique is to scan the sensor(s) back and forth as the robot drives around, giving a more comprehensive “picture” of the bot’s environment as compared to a stationary sensor. Parallax has a simple but ingenious PING)))Dar project, which servo-scans a PING))) sensor with a Boe-Bot’s BASIC Stamp 2 and “draws” the detected environment on the debug screen (Figure 3, courtesy

Figure 2.

loads/201409_Goodwin .zip) and was able to trigger motion with a pushbutton. However, in my own code, I noticed the servos tend to “jitter” around after they get to their intended position unless I issue this command: SERVOPOS TestServo1,OFF

Can you explain what’s going on here? Francis Procter St. Landry, LA

A

of Parallax). That’s an incredibly helpful visual aid to understand what the sensor actually sees. Check out the video at https://www.youtube .com/watch?v=t2tzBEOAtjg. If you only have a fixed sensor, your bot could stop occasionally and rotate in place to scan and detect obstacles.

Q

. After reading Steve Koci’s article on animatronics, I decided to purchase a PICAXE microcontroller with some servos. I started by downloading the example code for the DIY Animatronics kit (www.nutsvolts .com/uploads/magazine_down

. It could be several things. SERVO n, off turns off the PICAXE clock-generated servo pulses, so the servo is ‘disconnected’ and in a low power state. It may not hold position if there is a load on it. To eliminate or reduce glitches while SERVOPOS is actively driving the servo, you can try adding two commands at the start of your program. DISABLEBOD will disable the brown out detector, which may be causing problems related to power supply. DISCONNECT stops the PICAXE from periodically checking for new downloads, and has gotten me out of more than one jam. I had a problem recently when I used the serial input pin as an input on a robot. It’s normally pulled low by the download circuit, and in a pinch you can gain an input pin just by switching it to B+. It worked erratically; there was interference when the motors switched on. Turns out the long wires running out to my limit switch were acting like an antenna and picking up EMI, thereby resetting the PICAXE. All the motor filter caps in the world SERVO 02.2017

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couldn’t fix it, but DISCONNECT worked like magic. The only downside is that after DISCONNECT is used, you will have to do a “hard reset” to reprogram the PICAXE. That is, don’t turn on PICAXE power until after you click “Program” in the Program Editor. Another possibility is that you may have conflicts with pins and timers based on which PICAXE you are using. Manual 2 lists “conflicting commands” in Appendix 4. So, depending on exactly which pins and hardware and other commands you are using (any hardware serial, hardware I2C, hardware SPI, or interrupts?), you may have conflicts. Of course, make sure that your power supply or batteries and wiring are all sufficient for supplying the required voltage and power. I generally use a single power supply for the PICAXE and servos, but if your problems persist, try two different supplies linked by a common ground.

Q

. My daughter attended a FIRST LEGO League event and showed some enthusiasm for the whole thing. I am hoping to encourage her to explore STEM/STEAM by getting her a robotics kit to work with. Do you think I should go with the LEGO robotics kit they use for the competitions or is that too complex? Caitlin Berry Albuquerque, NM

A

. Good for your daughter! I have twin homeschooled daughters myself and am also interested in furthering their STEM (now it’s up to STREAM, sheesh) education. FIRST and LEGO have four different age ranges, and teams of girls and boys enter to compete but more importantly to have fun and learn. The LEGO League you mentioned

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Figure 4.

is for grades 4-8 and introduces kids to the LEGO MINDSTORMS EV3 system. I’m a professional toy designer and I have the utmost respect for LEGO and its fabulous products. You can’t go wrong with a MINDSTORMS kit. The EV3 system (Figure 4) should be around until ~2020, and even when a successor does come along, parts are typically reverse-compatible. While not cheap, it’s one of VERY few $350 tech toys with a 4.5 star rating on Amazon for a reason. It’s modular, open-ended, expandable, well-thought-out, and just plain fun. LEGO wrote the book on clear well-illustrated instructions. Your daughter can probably do it by herself, but it sounds like you would be a great helper and mentor for her. Obviously, LEGO League is about learning technology, but other incidental yet important takeaways are cooperation, partnership, and learning to be part of a team. You can certainly help foster the team and tech aspects at home, and hopefully find or even start a local team of similarly-minded students. What amazing opportunities our kids have today. Something other than cable TV and Facebook! Got a problem you need help with? Email questions to [email protected] and let’s see if I can help. SV

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NEW PRODUCTS Energy Propel Systems Combo Packs

H

itec’s Energy Propel motors are now available in convenient combination packs. With built-in programmable speed controls and high performance efficient motors, the Energy Propel line delivers the functionality and space-saving design multi-rotor projects require. Each bundle pack comes with two clockwise and two counter-clockwise motors to fully equip a rotorcraft and get it airborne quickly. Pricing begins at $121.88 and the combos are available in six sizes. Motor features include: • Motor and ESC combination provides a lightweight and space-saving alternative to separate components. • High performance, efficient motor. • Programmable speed control. • Updatable firmware.

Current-Sense Amplifier

T

exas Instruments (TI) has introduced a new currentsense amplifier for in-line motor phase current measurement that improves overall motor efficiency compared to existing current-sense amplifiers. The INA240 offers enhanced pulsewidth modulation (PWM) rejection for systems running at up to 80V to support a variety of applications such as motor control, solenoid control, and power delivery systems. Key features and benefits include: • Enhanced PWM rejection for improved motor efficiency: The presence of high speed inline PWM motor control systems requires high AC and DC accuracy. The INA240’s enhanced PWM rejection improves transient suppression and gives designers the ability to reduce their blanking time, optimize the motor control algorithm, and ultimately improve motor efficiency. • Flexible for a variety of motor applications: The INA240 operates at PWM rates in excess of 100 kHz, with switching-edge rates as high as 10 V/ns while enabling

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• BLHeli featuring active braking/damping light. • ONE SHOT synchronization protocol for faster communication between the flight control and ESC. • Simple wiring eliminates failure points. • Backed by Hitec’s one year warranty. For further information, please contact:

Hitec RCD

www.hitecrcd.com

system voltages as high as 80V. In addition, to address the needs for a wide range of systems, this device supports the negative voltages (-4V) induced by the inductive kickback of the motor. • Industry-leading performance and accuracy: The INA240 has one of the industry’s best combinations of low offset voltage (5 µV), offset drift (50 nV/°C), gain error, and drift performance (0.05 percent and 0.5 ppm/°C, respectively). The device also provides an excellent AC common-mode rejection ratio (CMRR) of 93 dB at 50 kHz. The INA240 delivers performance over a wide range of operating conditions. • Enhanced performance for any motor control solution: The INA240’s precision is showcased in a 48V 10A in-line three-phase high frequency Gallium Nitride (GaN) inverter for brushless motor reference design. This BoosterPack™ plug-in module reference design is paired with a C2000™ LaunchPad™ kit, demonstrating how designers can use the INA240 and LMG5200 GaN halfbridge power stage to reduce switching losses over an extended temperature range up to 125°C, facilitate the use

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of higher PWM frequencies, and reduce heatsinking requirements. Support is available in the TI E2E™ Community Current Sensing forum, where engineers can search for solutions, get help, share knowledge, and solve problems with fellow engineers and TI experts. As with TI’s entire current-sensing portfolio, designers have access to a full suite of support resources, including a complete library of TI Designs reference designs, evaluation modules (EVMs), online training series, and SPICE models. The eight-pin INA240 is available in a 3 mm x 4.4 mm thin-shrink small outline package (TSSOP). An evaluation module is available for $25. For further information, please contact:

www.ti.com

Texas Instruments

Is your product innovative, less expensive, more functional, or just plain cool? If you have a new product that you would like us to run in our New Products section, please email a short description (300-500 words) and a photo of your product to: [email protected]

EVENTS FEBRUARY 1-4

3-5

4-9

Kurukshetra Guindy, Chennai, India See website for details on this year's event. www.kurukshetra.org.in Quark Roboficial BITS Pilani KK Birla Goa Campus, Zuarinagar Goa, India Events include RoboKombat, RoboSumo, Line Following, RoboRace, and RoboKick. www.bits-quark.org AAAI Mobile Robot Competition San Francisco, CA See website for details on this year's event. www.aaai.org/Conferences/conferences.php

Events include Line Follower, Search & Rescue, Trash Hunter, Maze Solver, and an autonomous aerial vehicle contest. http://odturobotgunleri.org.tr 10-11

Midwestern Robotics Design Competition University of Illinois at Urbana-Champaign, IL See website for details on this year's event. http://mrdc.ec.illinois.edu

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Manitoba Robot Games Tec Voc High School Winnipeg, Manitoba, Canada Multiple events including Sumo and Line Following. www.scmb.mb.ca

23-26

Apogee BITS Pilani KK Birla Goa Campus Zuarinagar Goa, India See website for details on this year's events. www.bits-apogee.org

23-25

Festival de Robotique Montreal, Quebec, Canada Events include FIRST LEGO, FRC, FLL, and jrFLL. www.robotiquefirstquebec.org

MARCH 3-4

4-5

FIRST LEGO League of Central Europe Regensburg, Bavaria, Germany Championship event for FIRST LEGO student teams. www.first-lego-league.org/en/fll/regions.html METU Robotics Days METU Culture & Convention Center, Turkey

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bots

IN BRIEF

Working on the ChainFORM Gang

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s sensors, computers, actuators, and batteries decrease in size and increase in efficiency, it becomes possible to make robots much smaller without sacrificing a whole lot of capability. There’s a lower limit on usefulness, however, if you’re making a robot that needs to interact with humans or human-scale objects. You can continue to leverage shrinking components if you make robots that are modular; in other words, big robots that are made up of lots of little robots. MIT’s ChainFORM is an interesting take on this idea. It’s an evolution of the LineFORM multifunctional snake robot that introduces modularity to the system, letting you tear off a strip of exactly how much robot you need, and then reconfigure it to do all kinds of things. MIT Media Lab calls ChainFORM a “shape changing interface” because it comes from their Tangible Media Group. (If it had come from a robotics group, it would have been called a “poke-able modular snake robot with blinky lights.”) Each ChainFORM module includes touch detection on multiple surfaces, angular detection, blinky lights, and motor actuation via a single servo motor. The trickiest part is the communication architecture. MIT had to invent something that can automatically determine how many modules there are and how the modules are connected to each other, while preserving the capability for real time input and output. Since the relative position and orientation of each module is known at all times, you can do cool things like make a dynamically reconfigurable display that will continue to function (or adaptively change its function) even as you change the shape of the modules. ChainFORM is not totally modular in the sense that each module is not completely self-contained at this point. It’s tethered for power, and for overall control there’s a master board that interfaces with a computer over USB. The power tether also imposes a limit on the total number of modules that you can use at once because of the resistance of the connectors: no more than 32, unless you also connect power from the other end. The modules are still powerful, though. Each can exert 0.8 kg/cm of torque, which is enough to move small things. It won’t move your limbs, but you’ll feel it trying, which makes it effective for haptic feedback applications, and able to support (and move) much of its own weight.

The LineFORM as a lamp.

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bots

IN BRIEF PABI Offers Cost-Effective Therapy Solution

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he Centers for Disease Control and Prevention says about one in 68 American children has autism spectrum disorder. Therapy isn’t cheap at roughly $60,000 a year for the recommended amount of 40 hours per week of applied behavioral analysis (ABA) needed to effectively treat autism. The high cost is one of the reasons many autistic children don’t receive proper care. Fortunately, there’s growing evidence that robots can help. There’s a new robot called PABI (Penguin for Autism Behavioral Intervention) that is looking to make autism therapy more affordable. Developed by the husband-wife team of Gregory Fischer, director of WPI’s Automation and Interventional Medicine (AIM) Lab, and Laurie Dickstein-Fischer, Salem State University School of Education professor, PABI recently completed a two week pilot study with five autistic children, and the results were very promising. PABI, the robot penguin is 20 inches tall and 12 inches wide, with 12 degrees of freedom that autonomously conducts ABA therapy while logging therapy data that will be reviewed by a human therapist. PABI can move its beak, two wings, two eyes (independently), and eyelids. It also uses openCV 2.49 and 720p webcams to track a child’s facial expressions that can then be reviewed by the therapist. There’s a computer in PABI’s stomach that pairs wirelessly with a tablet to run interactive lessons for the children, as well.

Self-Balancing GyroCycle Soon to Hit the Big Slab

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otorcycles are about to take a big leap into the future. Thanks to a new prototype from Thrustcycle, self-stabilizing motorcycles could be cruising the streets in 2017. The GyroCycle keeps upright by using internal flywheels to create a gyroscopic effect. While this is generally felt by every rider at higher speeds, the stabilization here will occur even while standing still. An added benefit from the same technology is that the bike will be less likely to lose traction and slide under itself during a turn. This grants the rider greater control and increased safety. Self-balancing motorcycles could open up a new market for new and old riders alike. Those who are hopping on for the first time won’t have to learn how to balance such a heavy vehicle. Likewise, older riders often lack the strength to hold a motorcycle up. This has fueled much of the market for three-wheeled trikes. The GyroCycle would provide another alternative with a more traditional two-wheel design.

Price is going to be a big issue with such high-tech vehicles. This is where the GyroCycle is likely to edge out the competition. No official price has been released yet, but Thrustcycle has suggested that the price will be under $20,000. With multiple self-stabilizing motorcycles in development, it seems like we are getting one step closer to owning a Tron lightcycle.

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Post comments on this section and find any associated files and/or downloads at the specific article link for each feature.

BUILD REPORT: My First Antweight — A Dark and Dirty Disco Featured This Month: 18 BUILD REPORT: My First Antweight — A Dark and Dirty Disco by Ricky Matsko

21 An Interview with Ed McCarron by Brandon Davis

24 EVENT REPORT: Pennsylvania College of Technology SWORD Fights by Nate Franklin

26 EVENT REPORT: Robot Battles 61 at the Geek Media Expo by Thomas Kenney

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● by Ricky Matsko Warwick Robotics STL

hen it comes to robot building, it always seems to come down to the last minute. As a matter of fact, the first robot I ever built is named “10 Days ‘til Destruction” because the first parts for the robot arrived 10 days before my first competition. Back when there was just a month before Robot Battles 61 in Nashville, TN, I decided that it was time to design my first original Antweight robot. I quickly realized it’s incredibly tough to narrow down what kind of bot to build. After deliberating between a horizontal spinning blade, a full body spinner, a vertical bar

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spinner, and a lifter, I decided that I wanted to build a bot that resembled the dominant heavyweight combat bot, Biohazard. My main inspiration for the design of “A Dark and Dirty Disco” wound up coming from Equals Zero’s “Pad Thai Doodle Ninja” (www.etotheipiplusone .net/?cat=109). The only bot I’ve built before this one came from a Viper Kit with the spinner attachment. Prior to this, I had never worked in a CAD program. To make things worse, I wanted this bot to be 3D printed, but the printer I had access to only printed with PLA. If anything, I was preparing myself for

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FIGURE 1.

FIGURE 2.

the possibility that my robot could explode at any moment. After two weeks and several modifications to the robot’s design, I started to feel comfortable with the CAD program. At first, I thought I had to find CAD files of each part to import into the program so that everything was exactly to scale, but instead, I invested in a digital caliper to measure each part by hand. I would then create that part with the general shape and measurements to act as a placeholder in the CAD design (Figure 1). A majority of the electronics came from an additional FingerTech Viper kit that I had purchased, along with a few random eBay purchases. With less than a week before I left for Nashville, I had a fourwheeled/four-sided wedge with a rectangle acting as a temporary lifting arm in the design. Out of curiosity, I exported the file only to find that just the body — without the lid and lifting arm mechanism — was 20% overweight! The best thing I could think to do was cut the bot down from four wheels to two wheels, which would save me over two ounces in motors alone (Figure 2). It was about this time that a friend of mine offered to print the bot on his personal 3D printer using Taulman 910 Nylon, which has proven to be one of the best choices for 3D printed robotics.

FIGURE 3.

This was my big idea for how the lifter was going to work: a pin of some sort locking the lifter to the servo arm in the back and a middle support system in the front, based off a hinge. Is that stupid? Is that going to work? I don’t know! This whole build, I’ve had a “Hope this works!” attitude. I decided if it even remotely does “the thing,” I would consider that a victory! I got to designing the arm in the

CAD program, guessing how this whole system would work out. Eventually, this is what I came up with: it has a support pin in the bottom of the front hinge, which would be 3D printed out of 910 nylon.

Personal CNC Mills Shown here with optional stand and accessories.

Shown below is an articulated humanoid robot leg, built by researchers at the Drexel Autonomous System Lab (DASL) with a Tormach PCNC 1100 milling machine. DASL researcher Roy Gross estimates that somewhere between 300 and 400 components for “HUBO+” has been machined on their PCNC 1100.

PCNC 1100 Series 3 starting at:

$8480 (plus shipping)

www.tormach.com/servo SERVO 02.2017

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FIGURE 5.

FIGURE 4.

This build has pretty much gotten to the point of a YOLO (You Only Live Once) build. The back hinge and middle hinge would be supported by a nut and bolt system that is tightened down enough that the joint can move freely (Figure 3). With two days to go before I left for Nashville, I sent the parts off to be printed, hoping that everything would remotely fit. I attempted two “test-fit” prints with the PLA printer, but both failed due to separate issues. To my absolute surprise, when I got the nylon print, most of the parts fit fairly decently. Even better, the lifter

FIGURE 6.

actually did the thing! Figures 4 and 5 show what the bot looked like in the final stages before printing. The print wound up being pretty light at 13.65 oz. You can see I wound up having to use zip ties to hold the motors in because when I attempted to use the motor mount that was printed with the body, it snapped off. I wound up doing the same with the other mount, drilling holes in the sides of the remaining part of the motor mount, and zip tying the motors onto the body. So far, they have held up pretty well (Figures 6 and 7). Figure 7 shows the layout of the insides before doing some wire routing cleanup. As you can see, there’s a lot of Gorilla® tape holding things

down. I attempted to stack Gorilla tape high enough to where the lid would press down and hold the servo in place even better, but that would have required a lot more tape than shown. The receiver, battery, and tinyESCs in the back are being held down by Velcro®. The power switch was press-fit into a hole in the base of the body, and taped just for extra security and access. Things that I learned through this first design: • 3D printed motor mounts — no matter the material — can break very easily. (HINT: Make sure that your orientation is set up in a way to where the first time you attempt to use them, they won’t snap off.) • Tolerances are extremely important. I didn’t take tolerances into consideration at all, which led to a lot of items not really fitting all that great. I had to eliminate most of the

Parts List: ● 2x FingerTech TinyESC ● 2x DC 6V~12V 280 RPM Micro Mini Full Metal Gearbox Gear Motor ● 2x BaneBots Wheel, 1-3/8″ x 0.4″, 1/2″ Hex Mount, 40A, Black/Orange ● 2x Hub, Hex, Series 40, Set Screw, 3 mm shaft, 1 Wide ● FingerTech Master Power Switch ● HobbyKing 939 MG Servo MG ● Turnigy 500 mAh 3S 20C Lipo Pack ● FingerTech Power Terminals ● 2-6S Lipo BEC UBEC 3A 5V Input 5-23V ● Hobby King 2.4 GHz 6 CH Tx & Rx V2 (Mode 2)

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sidewall by the lifter which was meant to FIGURE 7. protect anything from getting inside the bot. The lid has to be taped down because the tabs in the front barely fit in the slots of the body; the screws I bought are not long enough to hold the lid down on the body. • Just go for it. Before this build, I had very little knowledge of Fusion 360, so I just kind of went with it. Try not to over-complicate and acts. At least the lifter arm the build (yeah, right!). I did a lot of extends in an up and out motion, just things in this design that are probably as I was hoping for. not ideal or “correct,” but I’m actually really happy with how the bot drives • Gorilla tape is your friend. The

stand that the servo sits in has pieces of nylon that are printed way too thin to really do much, so I decided to use the weight I had remaining to tape down all I could on the robot. As you can see from Figure 7, I taped down the servo, the lid, the motors, etc.

Unfortunately, due to a limited amount of “per team” entries, this bot did not compete at Robot Battles 61. Oh well. To see a video showing A Dark and Dirty Disco driving around, go to www.Warwick RoboticsSTL.com. SV

An Interview with Ed McCarron ● by Brandon Davis wanted to get to know Ed McCarron a little. He is one of the folks helping to run Robot Conflict events with NERC: the Northeast Robotic Club. Odds are excellent that if you live in the Northeast United States and have fought a robot in the last 15 years, you have seen Ed McCarron.

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Ed McCarron: I got started with robots early; been messing around with them since I was a kid. My dad worked with sheet metal, and made me a robot body that I never actually got moving. No idea whatever happened to it. Got into combat robotics, just like a lot of the crew here. Saw it on Comedy Central, Googled

around a bit, and found a group near me in Philly. I started competing in CJRC (Central Jersey Robot Conflict) events in 2000. Those were NERC’s first events. Got involved with organizing by default — I was the one there with the laptops when Fuzzy (Michael

First robot. Photo by Al Kindle.

Mauldin) ran his first LTRC (Lazy Toad Robot Conflict) event. Running it kind of fell to Beth and I. Brandon Davis: Talk about the most fun thing you ever built. EM: Too many to count. The DIY Arduino Segway my son, Josh and I built on a whim was pretty cool. The Rostock 3D printer we built from scratch was fun. BD: Other hobbies? EM: I’m heavily involved in Boy Scouts and a few other volunteer gigs. Not much time for hobbies. I read a lot. BD: The best bot in your stable? Why? EM: Netherbot — one of the first 30 pound pneumatic flippers. People said it would be tough to make it effective in that weight limit. It took a few SERVO 02.2017

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EO Row, Motorama 2016. Photo by Ken Franklin.

first place trophies, even if the name was odd. The worst was Spazhammer in 2006. A 24 pound Hobbyweight hammer robot that hopped. It fired pneumatic cylinders into the arena floor. A BASIC Stamp ran the whole show, reading the radio, sequencing the valves, firing the hammer. But even with a 100% weight bonus, I couldn’t squeeze enough valves in there to allow it to turn effectively. Lost two fights and never fought again, but I got that competition’s ‘Coolest Bot’ award. BD: If you could build anything you wanted, what would it be? EM: I’m fascinated by CNC tooling. I have my sights set on building a CNC gantry for my plasma cutter. BD: What was your favorite toy growing up? EM: Who says I’ve grown up? I’m 45 and still play with

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BD: Favored design aid? EM: I’m a fan of printing things Spazhammer. 1:1 on my laser printer and attaching Photo by Ed McCarron. the print to the material I’m cutting to use as a template. Still haven’t mastered working in 3D yet. BD: Favorite tool? ED: My bandsaw. Nothing beats treating aluminum like expensive hardwood. BD: What do you feel like the biggest change in combat robots is since you started? EM: Back when I started, we were still figuring out the difference between lexan and lucite, and using screwdrivers for drive motors. Now, stores have popped up everywhere online. Custom-made parts are easier to come by. Ditto for the CNC options available. The 2.4 GHz radios are definitely a great advance — and have made running an event much smoother. No more frequency clips, no more radio impound, and much more competitor-friendly to boot. BD: Talk about what goes into getting an event like Moto going each year. EM: A good bit of legwork. We're toys. I guess if you mean when I was fortunate to have a great venue and a a kid, LEGOs and Erector sets. That good event to work with. There are a silly RadioShack electronics kit with half dozen or so of us working on it, the springs. Anything that let you and we all have our little area of make something else. expertise. Jim Iocca handles BD: In 10 words or less, describe registration — which is by far the most your design philosophy. Make it thinky part of the whole thing. Jon different. Durand orders the tables and chairs EM: Doesn’t matter if it wins. and announces the event; Alan Young Have fun. and Al Kindle handle safety concerns; Joe Provenzano fixes just about everything there; I mail the paperwork out and set up the insurance; Beth (my very tolerant wife) handles the brackets and schedules the fights; and Zach O’Donnell injects common sense when needed. Then, we all come together at the event. After doing this for 10+ years, we’ve got it down to a science, I think. We just picked up a few new officers that will have to find their The view from the back at Motorama 2016. Photo by Ken Franklin. niche. Welcome aboard,

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Charles Guan, Kyle Singer, Brian BD: NERC has been one of Benson, Rob Masek, and Josh the singular successes of the US Zimmerman! There are a few robot combat world with wellother folks that consistently pitch attended events (for years!), in where they can. even in the “dark” time of no TV BD: There is a lot of stuff shows. What are some of the that you need to have an event. factors (in your mind) that Where do you keep it all? explain/account for this success? EM: The 16’ arena lives on a EM: We’ve tried hard to trailer, currently in Jim’s driveway. keep it simple and accessible. The rest of the paraphernalia Participation has grown and (scales, computers, clocks, etc.) fallen, but we’ve been lucky to lives in my garage in a few totes. have a dedicated group of The 8’ arena lives in a trailer in builders to keep us running. my driveway. The big arena was NERC wouldn’t exist without the built by Rob Masek around 2005. folks that engage in this goofy It takes a crew of about 10 hobby. Social media has made it working on and off for 16 hours slightly easier to get people to set the big arena up. The engaged — it beats standing small arena was built by Rob and around at a trade show handing Eric Scott in 2004, and goes up out brochures. in a few minutes. For years. Yeah. I’ve been Maintenance is handled as involved going on 15 years. Beth needed during setup normally, laughed when BattleBots™ was unless there are major repairs. on TV and they referred to one Ed McCarron and the old NERC arena, May 2012. Then, we’ll schedule a day to get of the teams as “Those kids Photo by Al Kindle. a few folks together to work on from MIT.” She said that only it. she was allowed to call them that The original arena — which since we’ve known them since was an 8’ x 8’ box four feet tall they actually were kids. similar to the small arena we still use today — was paid for by member donations and out of Folks like Ed are not only the pocket. NERC has been fortunate reason we are still fighting robots, that we are able to run on a very but contribute to the quality of low budget. We keep a low the robots we love to cheer by overhead. Since then, we’ve hosting and organizing the small mostly been able to pay for new weight class fights that form the arenas and upgrades with income bulk of our calendar. from events. “Minions needed.” Photo by Ken Franklin. BD: What’s the biggest You can keep up with NERC challenge? online at www.nerc.us. EM: Getting competitors to return BD: Any advice for people NERC sponsored events can be their paperwork on time. Seriously. considering getting an event going? found on the website. BD: What should folks know EM: It’s a lot of work, but the Robot Conflict’s extensive about NERC? payoff is immense. We all do this Photobucket (2000 to the present) EM: We’re always looking for because we love it and are passionate can be found at http://s1001.photo more folks to get involved in this crazy about it. Nothing makes me happier bucket.com/user/RobotConflict/libr hobby. We like teaching people what than seeing an event through to the ary/?sort=3&page=0. SV we do, telling them how they can get end. It’s a great feeling to know you involved, and hey, if they learn a bit helped pull this crazy thing together about something along the way, even and gave people from all over the better. I’m constantly using robotics to country a place to compete. That teach kids about physics, or feeling lasts about an hour, then you electronics, or whatever. As long as realize you have to do it again next they keep learning. year. SERVO 02.2017

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EVENT REPORT: Pennsylvania College of Technology SWORD Fights

● by Nate Franklin

ctober 22, 2016 marked the first ever SWORD (Student Wildcats of Robot Design) robot combat event at Pennsylvania College of Technology. The event was hosted by the club’s presidents, Mike Zalatan and Alex Horne. Thirty bots showed up to the event; the majority of them were first-time builders from the club. Robot combat veteran, Kyle Singer supplied the arena, which was his own 8 x 8 box with a push-out. He also served as the event’s commentator, and helped load and unload bots during the event. His humorous commentary helped keep the crowd entertained, and he did a good job explaining the rules to the new builders. Four Antweight bots fought in a double round-robin tournament. The competitors were wedges Slim Pickens and Discharge, as well as horizontal spinners Don’t Ask and Ready or Not. In round 1, Slim Pickens won a tactical

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The arena and pits.

fight against Discharge, and bullied Don’t Ask with ease. Meanwhile, Ready or Not beat Don’t Ask, but lost to Discharge after self-destructing. In the next round, Discharge beat Don’t Ask a second time, but lost to Ready or Not after accidentally driving into the push-out. Slim Pickens went undefeated, beating Discharge and Don’t Ask again, and getting an easy victory over Ready or Not (this was the first time the two met, since Ready or Not had to forfeit in round

1). Both Discharge and Ready or Not were tied for points, and fought a tiebreaker match to decide second and third. Discharge got the win to secure a second place spot Twenty-six bots were entered in the Beetleweight division. The tournament format was different from standard events held in the US. Taking

Scrambles the Death Dealer.

Don’t Ask.

Slim Pickens. Discharge (left) and Tiny (right).

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Ready or Not.

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a page out of events in the United Best Korea Kingdom, the event had two stages. Clone. Shrapnel. In the first stage, the bots were randomized and fought in three-way rumbles. Each bot was guaranteed three rumbles, and received points based on their performance. Winning by KO is four points, and a judge’s decision is three. The bot in second place gets two points, while the third place bot gets one point. The eight bots with the most points would move to the second stage: a single-elimination knockout the win. The wedge of Thunder Child tournament. proved to be unstoppable in its The Beetleweights featured bots qualifying rumbles, bullying all of its from students, faculty, and a few opponents. outsiders. They included some vertical When the rumbles were finished, spinners like Riptoff 3, GOAT, and six bots had enough points to go to Tiny. Best Korea Clone, Shrapnel, and the next round: Thunder Child, Tiny, Thunder Child. Scrambles the Death Dealer were a Shrapnel, Wildcat, Circuit Breaker, and few of the horizontal spinners that did Riptoff 3. Because there were two some great damage, but ended up other places left in the single self-destructing one way or another. elimination bracket, four bots that had decide who continued on. GOAT, One of the more unique bots was almost enough points to go through Blender, Dz Wedge, and Mr. Happy Potbot, a bot made from (you had to fight in a four-way rumble to entered the arena, with the latter two guessed it) a pot. It used moving through to the next three brushless Outrunner stage of the competition. motors wrapped in duct tape In the single-elimination to spin around the arena. stage, it was make or break In the opening fight, time for the remaining bots. eggbeater Wildcat proved to In round 1, Thunder Child be vicious, but suffered from quickly disposed of Mr. weapon belt issues Happy; Wildcat outpushed throughout the event. It took Shrapnel after both bots lost Circuit Breaker (left) takes on No More Bubblegum (right). on abrasive disc spinner Apex their weapons early on; and Killawatt, made from a Circuit Breaker pummeled computer’s power supply. Riptoff 3; and Tiny tore the Things started to get wedge off of Dz Wedge. Riptoff 3 (left) fights GOAT after Potbot intense when horizontal In the semi-finals, (background) is left spinner Circuit Breaker came Thunder Child was able to upside down. into the arena shortly after, disable Wildcat’s weapon belt proving to be the most vicious and win a one-sided push spinner in the competition, fight. Meanwhile, Circuit taking out No More Breaker put on a show in its Bubblegum and Lethal Lotus semi-final fight as it brutally in its opening fight. disposed of Tiny to reach the Meanwhile, Riptoff 3 final. Wildcat got third place took on fellow vertical spinner by default, as Tiny could not GOAT and Potbot, disabling be repaired in time for the the former’s weapon and third place playoff. putting the latter on its back. While the two remaining Unfortunately, Riptoff 3 bots prepared for the final, ended up throwing its own the Beetleweight rumble was weapon pulley, but still got held. It featured a total of 12 SERVO 02.2017

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Wildcat (center) fights Apex (left) and Killawatt (right).

(From left to right) GOAT, Dz Wedge, Mr. Happy, and Blender fight for a place in the singleelimination bracket.

The Beetleweight final was downright Circuit Breaker brutal. Thunder Child disposes of Tiny. charged headfirst into Circuit Breaker several times, sending it ricocheting around the arena. Circuit Breaker got the upper hand, as it managed to tear off Thunder Child’s back wheels. Thunder Child after the final. Thunder Child didn’t give up, and kept fighting on despite being reduced to 1st 2nd 3rd Rumble limping. Antweight Slim Pickens Discharge Ready or Not N/A Circuit Breaker’s battery began to die, Beetleweight Circuit Breaker Thunder Child Wildcat Shrapnel but was saved by the bell. After the three minutes were up, the judges gave the win to Circuit bots, in an all-out five minute slugfest. In the end, the Breaker. SV horizontal spinner Shrapnel came out on top.

EVENT REPORT: Robot Battles 61 at the Geek Media Expo ’s GMX Robot Battles were held on the Sunday of Halloween weekend in Nashville, TN. This was the fifth official Robot Battles event in Music City, featuring the return of Kelly Lockhart as MC, and a much larger arena than in previous years. The turnout was high, with seven 3 lb Beetleweights and 14 1 lb Antweights competing, aided by a record number of out-of-state teams.

● by Thomas Kenney

2016

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Volunteers assemble the arena.

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www.servomagazine.com/index.php/magazine/article/February2017_Robot-Battles-Geek-Media-Expo.

Antweight Miscleant and Beetleweight Mechanical Resonance.

Builder Glen Gibbs repairs his Antweight A Worker.

The event got off to a hectic start, with the arena arriving almost an hour later than anticipated. Over a dozen volunteers from the pits grouped together to assemble it as quickly as possible, allowing the fights to begin soon after the planned time. The Antweight brackets — single elimination due to time constraints — were swept by three lifters and a quick aggressive wedge. The two wheeled wedge-lifter Proteus (with its large wheels and polycarbonate construction) outdrove the competition in its first two rounds, beating drum spinner IDK and the undercutting bar spinner A Worker; named such for the meaning of a Mandarin character the frame’s body resembled. Veteran wedge Gilbert pitted the Antweight rumble.

vertical saw of Green Reaper 6.0 in only four seconds, then bullied Miscleant around the box before the latter encountered radio issues and tapped out. The newly built forward lifter Misdirected Pedestrian managed two near identical victories in its first matches against a pair of horizontal undercutters (both modified FingerTech Viper kits) by disabling their weapons and stacking them immobile against the arena wall. Finally, Vee Parr (a FingerTech Viper kit with the lifter attachment) defeated the drum spinner IDK with help from the latter’s weapon malfunctioning, and

then outdrove the wedge George Reloaded. Vee Paar and Misdirected Pedestrian met in the first Antweight semi-final. Though evenly matched at first, the battle turned towards Vee Parr’s favor as Pedestrian began to experience issues with its drive transmission, allowing the Viper kit to throw its opponent into the push-out in dramatic fashion. Gilbert and Proteus’ semi-final match went the distance. Proteus’ polycarbonate wedge was no match for Gilbert’s razor-sharp hardened steel. However, to maintain its inevitability in the face of Proteus’ lifter, Gilbert fought without its usual horned appendages, and was unable to control the opponent well enough to end the fight with a push-out victory. The results went to the judges, who declared in favor of Gilbert. To avoid the indecisiveness of the previous match, Gilbert’s horned appendages were Builder Azeem Hussain reattached in the final, with Antweight IDK and Beetleweight Revenge of at the risk of the Klukz. noninvertibility in the SERVO 02.2017

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Antweight fight. Who Cares? is upended by Misdirected Pedestrian.

Beetleweight fight. Ghost is shoved by Wedgee.

face of its lifter-armed opponent. The bet paid off, and before 20 seconds had passed, Gilbert had

swept under Vee Parr and driven its opponent into the pit, securing its first Antweight championship since being

Builder Patrick Becker with Antweight Green Reaper.

temporarily retired in 2012. As with last year’s GMX Robot Battles, the Beetles were dominated by Ben and Mark Hanson’s two robots: Wedgee, a two-wheeled wedge driven by antique Handiworks gearmotors, and Flippy, a KitBots’ drum spinner. Most of the other competitors were new or recently built spinners. These included STEVE, a full body spinner from a University of

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Minnesota team; Mechanical Resonance, a horizontal midcutter built in a week by veteran competitor, Will Evans; and Revenge of the Klukz, a sleek welded steel tank fitted with a KitBots’ eggbeater. The opening match of the Beetleweight double-elimination brackets featured Mechanical Resonance winning a judge’s decision over STEVE, whose weapon was nonfunctional but managed to survive thanks to its opponent’s 15 year old BattleBots™ toy gearmotors failing. In the following matches, Flippy and Wedgee won decisive push-out victories over the horizontal spinner ZOU Keeper and Revenge of the Klukz, respectively. Mechanical Resonance was pitted against fellow midcutter Ghost in the next round, but quickly tapped out after one of its wheels rolled off just

Beetleweight rumble.

one second into the match. Wedgee beat teammate Flippy in the following match, and then won an easy push-out victory against Ghost in the winner’s bracket finals. With only one Team Wedgee robot, the Beetle loser’s brackets were more contested. ZOU Keeper fought its way past both Revenge of the Klukz and Mechanical Resonance before meeting defeat by the eggbeater of Flippy, who then went on to defeat Ghost in the loser’s bracket finals.

For the second time, builder Tom Spaulding guest drove Flippy while Team Wedgee’s usual driver, Ben Hanson piloted Wedgee. Ben handily won via push-out, giving Wedgee another in its long line of first place finishes, and further validating the decade-old design. Two action-packed rumbles capped off the event, serving the final round of damage that local builders hoped to have repaired in time for Robot Battles 62 at Chattacon in January 2017. SV

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DIY Animatronics Servos: The Basics and Beyond

By Steve Koci

What can servos do for you? Well, they will not give you relationship advice or make you coffee, but they can help you create some extremely lifelike characters. I think they could actually make you coffee, but that is a topic for another time.

T

regarding the operation of servos have aking the step into using servos been well documented in other articles can be intimidating. Most of us here, but I will cover the basics for any are used to moving a mechanism newcomers to the hobby. It is necessary to by simply providing power to a be familiar with the basic concept before motor. In reality, servos are delving into the more advanced. This simply motorized gearboxes which have the explanation will help you choose models ability to move to a specified location using that best fit your needs. a control signal. You do need to add Becoming comfortable using servos and something to provide that input — whether taking advantage of all the added features it is an RC transmitter or a microcontroller available will expand your capabilities as a — but that does not have to be a difficult builder. So, let’s take a look at why they are process. There is a wide selection of so special. different controllers now available that take much of the complication out of that part of the equation. In addition to looking into the workings of servos, I would like to discuss the use of Servos are made up of four basic digital servos and the added benefits they components. These are a motor, gear set, can provide. The trend seems to be moving potentiometer, and control board. You will away from analog servos to the digital find that the first three of these are the models, so we will examine a few of the same when comparing an analog servo to a contributing factors for this shift. I am a big digital model. The difference comes when fan of the digital models although I still looking at how the signal is processed and utilize a few analog servos (primarily the used to send power to the servo motor. Hitec 485HB) in my three-axis skulls. The gear set slows the motor speed This will not simply be a review of the and increases the torque delivered to the Figure 1. Actobotics to the rescue! workings of these extremely useful and servo shaft, while the potentiometer — versatile devices. We will take a look at a which is connected to the output shaft — few alternative servos that you may not have previously provides location feedback of the horn position to the considered. I will also demonstrate how a stand-alone controller. servo’s durability and power can be further increased by There are many different brands of servos available including them in a system such as the Actobotics with Hitec, Futaba, and JR being the big names, but there products from ServoCity (see Resources). My characters are plenty of more budget-friendly brands available rely heavily on these and quite frankly, I could not achieve (Figure 2). If these fit the bill for you, check them out the same results without a tremendous amount of thoroughly before investing heavily in them. I personally additional effort (Figure 1). have not been very satisfied with the performance and I am aware that the basic concepts and explanations durability of the budget-friendly brands I have tried, but

What Makes Them Tick?

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DIY Animatronics Post comments on this section and find any associated files and/or downloads at www.servomagazine.com/index.php/magazine/article/February2017_Animatronics_Servo-Basics.

your mileage may vary. I use models from Hitec as they are the ones I am familiar with. A highly useful chart for comparing the features of many of the Hitec servos can be found at http://tinyurl.com/ zf54oy4. There is not a proprietary system in place for servo design. As an example, the neutral position for a Hitec servo is set for a 1,500 μs pulse width while it is 1,520 μs on a Futaba Figure 2. There are options besides the big name brands. servo. Again, comparing just the Hitec and Futaba brands, they have different spline sizes, connectors, and primary rotation direction settings. So, do a little research when selecting your servos to be sure of their features. I suggest finding a brand you like and sticking with it. It will be much simpler to standardize your designs and to stock replacements and spare parts. Granted, it is possible to work with these differences, but why complicate the process unnecessarily?

This is a situation where one of the smaller servo models may fit the bill. You can select from nano, sub-micro, micro, and mini sizes in both analog and digital versions (Figure 3). Giant — There are times where you must move from the traditional and go BIG (Figure 4). This is the category where the big brothers of standard servos can be found. Their larger size provides the space for a heavier duty motor and larger gear to provide the strength to satisfy greater performance requirements.

Torque

When choosing a model to use, it seems that the primary consideration is how much torque a particular servo will provide. Determining how much torque your mechanism requires can be a bit tricky. The proper explanation is how many ounce/inches (oz-in) or kilogram centimeters (kg-cm) it can hold one inch from the shaft at a certain voltage. For example, one of my favorite servos — the Hitec Figure 3. Good things do come in small packages. Servos come in a variety of 5685MH — can produce 194 sizes from the micro all the way up oz-in (14 kg-cm) when powered at to quarter scale. The most popular 6V. If I were to increase the servo size is the standard dimension arm length from one inch to two servos which provide the greatest inches, it would now only manage selection. 97 oz-in. However, if I were to Oftentimes, the choice is made reduce the length by half, it would for us by the space constraints of now provide 388 oz-in. our projects. Besides the standard While that information is size models most of us begin with, useful in comparing servos, most there are other options available of us use a more seat-of-the-pants including the following: method to choose the correct model for our projects. A little bit Mini Servos — There are many of experience and having a few design applications where we do different models on hand when not require a tremendous amount prototyping a design will go a long of torque or where space is limited. way in ensuring your mechanism Figure 4. Go big or go home!

Size

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DIY Animatronics with the brushless models getting the nod for increased performance. The material used for the gears can be plastic, Karbonite, metal, or titanium. The performance differences can include wear resistance, strength, and how quietly they operate. Titanium gears offer the best performance but you will, of course, have to pay a premium for them. The number and type of bearings will contribute to the smoothness of operation as well. You can choose from plastic, metal, or ball bearings. It is hard to beat the smoothness of dual ball bearings! Figure 5. Servos can be installed in tight spots.

Cost Figure 6. Who’s afraid of a little rain?

has all the power it needs. If you are unsure of how much power your mechanism will require, I suggest that more is better! I have not ever had this philosophy fail me.

Speed Servo speed is defined as how long it takes to move the servo horn 60 degrees, again at a certain voltage. While not usually as critical of a design factor as the torque, it still needs to considered. I have found that faster is not always better. When assembling Jarvis (see the September 2016 issue of SERVO Magazine), I found that I was able to get smoother body movements when using a slower servo. We will discuss how you can program your digital servos speed in a bit. Sometimes it takes some experimenting to achieve the exact motion you are looking for. There is a trade-off between speed and torque, so you need to consider where you are willing to compromise.

Voltage Servos can usually be powered by a range of voltages; often between 4.5 all the way up to 7.4 volts. By using a higher voltage, your servo is able to deliver more torque. Improvements in battery performance have allowed us to use higher voltages and remain within our build parameters.

Construction The internal components used in the construction of a servo vary as well. Motors can be coreless or brushless,

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As with most things, if you want more features, you are going to pay a bit more. Digital servos are more expensive than their analog cousins, but in my opinion are worth the extra expense. Selecting a servo that is within your budget is an important consideration. Take into account such things as the difficulty in replacing a faulty servo. Is this a temporary project or something that is expected to last long term? Is the continual operation of a particular servo of high importance? Sometimes it is advantageous to pay a higher upfront cost than to make repairs later.

Have You Considered These? I would like to take this opportunity to point out several specialized servos that you may not have considered before. These fulfill some unique requirements and you should at least be aware that they are available if you need them. Flat — When your only available space is a narrow slot, the HS-7115H servo may fit the bill (Figure 5). It is super slim and still provides 50 oz-in at 7.4V. It includes a titanium gear train and dual ball bearings, giving it plenty of strength. Continuous Rotation — Have you ever wanted to be able to create a winch for a project? Maybe a continuous rotation servo such as the HSR-2645CR will solve your problem. While it has no potentiometer to provide feedback, it can still be a useful device to add to your toolbox. Waterproof — Some applications may require you to have a waterproof servo. The D845WP model delivers

Koci - Animatronics - Feb 17_Steve Koci Animatronics #1 Parrot.qxd 1/2/2017 9:16 PM Page 33

DIY Animatronics

Figure 7. A portable programmer that goes where you go.

Figure 8. Programming from your computer.

incredible torque of 694 oz/in at Figure 10. Channel 7.4V, and is one of the new D mount gearboxes for more power. series servos (Figure 6). This servo offers some significant improvements, including the ability to accept a wide voltage range of Figure 9. Servo blocks provide a strong skeleton. between 4.8V and 8.4V. It incorporates steel gears and dual ball bearings to go along with its high resolution. In order to fully utilize all the features of digital servos, you will want to have a programmer. I just picked up the Quality servos are available from a number of different new Hitec HFP-30 which is compatible with all of their sellers including ServoCity, Pololu, SparkFun, RobotShop, digital servos including the new D series (Figure 7). It also Parallax, and Adafruit. I have provided links to their sites in doubles as a universal tester (see Resources). In addition to being a servo tester, the HFP-30 the resources section. programmer allows you to access and adjust a slew of features. The ones I find most useful are the ability to adjust the speed and the direction of the shaft’s rotation, Now, it is time to examine the benefits that moving as well as the capability to select your end points. from analog to digital servos can provide you. Be warned You also can adjust the deadband width, the neutral that once you try them, you may never go back! points, fail safes, and the resolution, as well as select The primary components of a digital servo are the whether you want the overload protection enabled. The same as those in analog servos. Their magic comes from large screen makes for ease of reading. The battery is how the signals are processed when providing power to external, so make sure you have one with the necessary the servo. The advantages of choosing a digital servo over connector available. an analog model include the fact that digital servos have Another option that may work for you is the DPC-11 increased holding power, decreased deadband (neutral dongle PC programmer. This computer interface is zone), and are quicker to respond to input. compatible with some of their servos, so check the specs This is a result of the higher rate of command pulses it to see if it will work for you (Figure 8). receives, allowing it to update its position more frequently. The flip side to this choice is that digital servos are more expensive and consume more power than an analog servo. The ability to increase your servo’s performance is By adding a programmer to your toolbox, you can possible by including them in a system that has the ability unlock many of the user controlled options available when to augment the available torque and increase the load using digital servos. bearing capabilities. These objectives can be met by

Servo Programmer

Digital Servos

Actobotics

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DIY Animatronics be considerably utilizing the more stable. The Actobotics system model I am starting from ServoCity (see with is extremely Resources). powerful and is Servo blocks admittedly overkill, significantly increase but I will never the mechanical load need to worry a servo can handle about it failing. It (Figure 9). The incorporates a giant standardized layout HS-805MG servo, allows a multitude delivering 1,715 ozof configuration in of torque (Figure options when 12). combined with other Actobotics components. If it is more torque you need, You servo gearboxes add occasionally need an external gear set to test to see if a to boost the Figure 11. Original shoulder twist Figure 12. Improving upper body servo is functioning available power. In design. rotation. properly. This is addition, the where a reliable tester comes in gearboxes provide a tremendous handy. There are plenty of amount of support to the inexpensive testers available, but external shaft, allowing it to hold my favorite is a Do-It-Yourself up to the added forces being two-channel model put together applied to the servo. The by a fellow builder (Figure 13). gearboxes come in several Tyler’s original post and a link to different mounting options. I use a follow-up post with a link to the the channel gearboxes extensively needed files can be found at in my characters when constructing the body www.haunt forum.com/show mechanisms (Figure 10). They fit thread.php? t=3507. This unit inside the channel which has the added ability to output produces a remarkably clean the actual endpoints if you need design. to add the numerical settings into I am currently in the process your microcontroller program. of changing the way I rotate the upper body of my characters. In the past, I had a rigid spine to For a quick and easy which the shoulders were Figure 13. A DIY servo tester comes in handy. mounting solution, check out the attached. A servo and gear set brackets from RobotShop (see was added to the top of the spine Resources). They fit a standard and would turn the head and size servo and provide a shoulders (Figure 11). This convenient and secure system has worked well, but it attachment (Figure 14). will occasionally skip a gear under heavy load or if it needs to move quickly back and forth. In order to solidify this portion of my design, I am going with a bottom flange gearbox to which the spine will be mounted atop. This will allow the entire In order to take full upper body to rotate and should Figure 14. Mounting servos made easy.

Servo Tester

Mounting Brackets

Other Accessories: Wiring Extenders, Cable Locks, and Splitters

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DIY Animatronics advantage of your servos, you will want to pick up a few accessories. You can never have too many servo extensions for when you want to place your controller away from your servos. When placing your order, be sure to get extensions which have a male and a female connector, not servo cables. I am always in need of more extensions, but now have more servo cables than I will use in a long time. When running your wiring, it is recommended that you err on the side of them being too long. You want to be sure you have enough slack through the entire range of motion of your mechanism. A bit of extra security can be had by adding cable locks to keep any extensions from coming detached (Figure 15). There are times when you want a single controller channel to send signals to two servos. This is a case where a splitter comes in handy. Both servos receive the same commands, but it is one option for increasing the number of servos a single controller can handle.

Figure 15. Secure your wiring connections.

Servo Arms You have your choice of a variety of servo arms that come with your servo. There are other options available for purchase separately if the stock ones do not fit your needs (Figure 16). Check out some of the alternatives at http://tinyurl.com/hdrzb4d. You do need to pay extra attention to the spline size to make sure you get the proper one.

Cable Extensions You can place your servos a distance away from the point where they are creating movements by using cables running inside of a housing such as those available from Sullivan Products (see Resources). Watch for an upcoming article showing exactly how to incorporate these into your builds.

RESOURCES ServoCity/Actobotics — http://tinyurl.com/zzy2ugu Hitec RCD Programmer — http://tinyurl.com/j2rv38d Adafruit — http://tinyurl.com/hadoqb2 RobotShop — http://tinyurl.com/gnkb47m SparkFun — http://tinyurl.com/lpgxyfu Parallax — http://tinyurl.com/om7pqoy Pololu — www.pololu.com RobotShop Servo Brackets — http://tinyurl.com/zpczhhs Sullivan Products — http://tinyurl.com/hoqh982 My YouTube channel — http://tinyurl.com/nma2doj My Website — www.halstaff.com DIY Animatronics Forum — http://tinyurl.com/qjeehjs

Figure 16. Pick a horn, but not just any horn.

Now You Can Servo Yourself If you have yet to take the plunge and include servos in your projects, now may be the time. I especially encourage you to check out how digital servos can help you become a more successful builder. Eventually, we may have no choice but to use digital servos as this seems to be the direction the industry is trending. So, why not take advantage of all they have to offer now? Have you incorporated servos in a unique way into one of your projects? Do you have questions or comments you would like to add to the discussion? Then, visit the DIY Animatronics Forum at http://tinyurl.com/qjeehjs and join the conversation. We can all contribute our ideas in order to benefit the community! Until next month, MAY THE PASSION TO BUILD BE WITH YOU! SV

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Serving Raspberry Pi

#9

By William Henning

In the last article, the accuracy of the heading produced by our Raspberry Pi bot, Berry's compass was greatly improved by adding magnetic declination and tilt compensation. However, that by itself is not enough for indoor navigation. At the very least, I need to add odometry so that I tell Berry to “go forward 0.5 m.” ’ll need a few more upgrades first, however. Berry’s head kept falling off. (Okay, you can stop laughing now.)

I

FIGURE 2.

Berry will no longer lose his head. The Sharp 10 cm-80 cm IR sensor made Berry short sighted, so instead of trying glasses, I added a generic HCSR04 ultrasonic distance sensor since an HC-SR04 ultrasonic ranger has a four meter range — greatly improving Berry’s detection area.

Re-Mounting the Sharp IR Sensor FIGURE 1.

As a temporary measure, I mounted a 9g micro servo on top of the chassis by simply using double-sided foam tape to hold the servo, and more double-sided tape to hold the Sharp IR sensor on the servo horn (Figure 1). It worked. Nonetheless, the servo kept tilting, and Berry kept losing his head. I had some inexpensive acrylic servo mounts, so I used one to mount the servo on Berry. I kept the double-sided tape on as well, so the servo is mounted “real good now.”

The problem with the panning ultrasonic head is that it would not prevent Berry from falling down stairs or running off a table. I mounted the Sharp IR sensor on Berry’s lower deck, pointing down slightly (Figure 3). This way, Berry can use it to watch for: • Objects that are close by, while the HC-SR04 can pan for farther objects

Adding a Better Servo Unfortunately, the servo mount did not fit my blue 9g servo perfectly. Fortunately, I had slightly bigger ones, with better servo horns to boot! As I did not want Berry to constantly lose his head, I also mounted one of my sensor holders on the servo horn (Figure 2).

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FIGURE 3.

Henning - RaspPi Bot - Feb 17_Blank Rough SV.qxd 12/30/2016 4:31 PM Page 37

Giving Berry a Better Servo Mount Post comments on this section and find any associated files and/or downloads at www.servomagazine.com/index.php/magazine/article/February2017_RaspPi-Robots-Better-Servo-Mount.

• Sudden drop-offs (stairs, table/platform edge, etc.) After I find the “perfect” angle, I’ll make a better holder for the IR sensor. For now, I used (wait for it) double-sided foam tape again (Figure 4).

Odometry Simplified Odometry is simply measuring how far your robot has travelled. Go to https://en.wikipedia.org/ wiki/Odometry to get more details. The odometer in your car keeps track of how far you have travelled, based on how many times your drive wheel has rotated and the diameter of the tire. We can pretty much do the same thing for Berry by using sensors to figure out how many times one of Berry’s tires has turned. Looking at a photo of Berry, you can see that his tires have five thin spokes separated by five empty spaces (Figure 5). By using a simple reflective light sensor mounted in such a way that it can “see” the spokes, we will be able to count the spokes as the wheel turns. Every five spokes, the wheel has turned a full 360 degrees. The circumference of the tire is pi times the diameter (i.e., pi times twice the radius), so once we know how many revolutions Berry has travelled, we can multiply it by the wheel’s circumference, giving us the total distance travelled.

FIGURE 4.

As the wheel’s diameter is 64 mm, one revolution of the wheel travels pi*64 mm, which is 201.06 mm (or 7.91 inches). Of course, this measure will be a little misleading, as it does not account for going backwards or spinning in place. Not to mention a wheel travelling on the outside of a turn will travel farther than the wheel on the inside of the turn. Fortunately, we can account for these issues! The easiest way to NOT count the distance the robot spins in place is to simply stop accumulating the distance travelled until the robot stops spinning. To account for the different turn radius per wheel, we have to accumulate the distance for a wheel on each side of Berry, then correct for bends.

Adding Wheel Encoders I tried to use two of my SirMorph reflective sensors. I attempted to attach them to Berry in such a way that they would get a good reading of the wheel spokes. Unfortunately, there was not enough room to mount them successfully on this chassis. Since I did not want to mount the sensors on the outside of the wheels (thus increasing Berry’s girth), I decided to make two smaller sensors that I could attach to the “bottom” of the motors and push into the empty space in the wheel (Figure 6). FIGURE 6.

FIGURE 5.

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I needed to get the sensor closer to the wheel spokes in order to get more light reflected onto the sensor, allowing me to better discriminate between the spokes and the spaces between the spokes. I keep a stock of TCRT5000L reflective sensors, so I just needed a way of wiring them up and attaching them appropriately. To keep the sensors small, I used male-female DuPont jumpers over the legs of the TCRT5000L sensors (Figure 7). I then used one of my prototyping boards to add the resistors, and more DuPont male-female jumpers to run 5V, GND to the board, as well as run the two analog signals back to RoboPi. There is plenty of space left on the prototyping board if I decide to add an op-amp to increase signal gain, or any other circuit to improve the encoder’s performance.

It worked! We can clearly see that the “spokes” reflect light, and are a lot narrower than the space between the spokes (Figure 9).

FIGURE 9.

Calibrating the Encoder It’s time to write a calibration utility to find the minimum, maximum, and average light level reflected by the spokes: FIGURE 7.

pi@Berry:~/robopi/Python_Demos $ python berry.py Berry Encoder Calibration Test RoboPi http://Mikronauts.com API v0.97x

Testing the New Encoders I hooked everything up, and started with a small test program that ran both of the motors that I attached sensors to at full speed, printing out the analog reading shown in the figure from the phototransistor in the TCRT5000L (Figure 8). FIGURE 8.

Capture of 500 samples took 11.1943240166 seconds Analyzing Motor A data... Motor A min 87 avg 152 max 301 Analyzing Motor B data... Motor B min 94 avg 153 max 327 Motor A calibration value is 152 Motor A calibration value is 153

If you change motors or the position of the encoder sensor, you need to recalibrate. Okay, now that we have the calibration values, we can decide if a spoke is close by.

Finding Spokes Let’s add code to count the number of “high” and “low” periods for the length of the test run. High and low periods are counted as follows: - If we are X% above the average, we are in a HIGH

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(spoke) state. - If we are X% below the average, we are in a LOW (space) state. X% is currently set at 20% of the full range (max-min) and needs to be tuned for different wheels. This leaves a 40% dead band around the average, allowing us to ignore minor fluctuations in light level. Guess what? • We know how long the test ran. • Now we have the number of high (spoke) and low (space) periods. • We know there are five spokes on these wheels. • That means there are also five spaces.

I attached a piece of red electrical tape to the wheel, and counted the number of revolutions made during the calibration run. Good news: It matched the calibrated RPM value that Berry calculated. Bad news: There was a ~25% difference in RPMs between the front right and left motors. I will be upgrading Berry’s motors in one of the following ways: • Matched motors (within 5% or less of each other) • Four independent motor drivers so I can “tune” the PWM speed per motor I will let you know how it turns out! SV

So, we know there are 10 pulses (five low, five high) per revolution of the wheel. Hmmm ... If we ran the test for 60 seconds, counted the number of (high+low) pulses, and divided by 10, we have the average RPM for the length of the test! Actually, as long as we run for more than two revolutions and know how long it took to compute the scan, we can calculate the RPM:

The upgraded Berry Bot.

Computing Motor A RPM: 238 pulses, so 23.8 revolutions in 11.1943240166 seconds means Motor A ran at 127.564647752 RPM Computing Motor B RPM: 190 pulses, so 19.0 revolutions in 11.1943240166 seconds means Motor B ran at 101.837323836 RPM

Motor to Motor Variations in Cheap Motors I knew that the rock-bottom cheap motors I was using were not very accurate. After all, I could see Hobbit, Elf, and Berry would not go straight when driving the motors at the same voltage. However, I was still surprised at the ~25% variation in unloaded maximum RPM — so much so that I had to verify my findings.











   

  




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Building the KReduCNC

By Michael Simpson

Spindle Hookup It has been a while since we started this project, and it’s time to make some chips. In this installment, we’ll go over spindle hookup. Post comments on this section and find any associated files and/or downloads at www.servomagazine.com/index.php/magazine/article/February2017_Build-CNC.

What is a CNC Spindle? A spindle is the rotation portion of a CNC machine on to which a cutting tool is attached. While technically the spindle is the shaft itself, it has become common place to refer to the motor and shaft assembly as the spindle. There are many shapes and sizes of spindles. First, let’s look at low speed and high speed versions.

Low Speed Spindles Low speed spindles are used primarily in machines that need to do milling operations on metal. They are needed when drilling larger holes may be required or for turning very Figure 2

Figure 1

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Figure 3

large tools. Milling machines like the one shown in Figure 1 use a low speed spindle. This spindle will run at a range of 500-2,500 RPM. Since most motors don’t run slowly enough, a belt or gear reduction is used to slow down the spindle shaft in most cases. Needless to say, we won’t be using a low speed spindle on the KReduCNC.

High Speed Spindles Most CNC machines designed to mill wood, plastic, and some non-ferrous metals use a high speed spindle. While there are several varieties, I will be talking about two types: routers and rotary tools.

Routers Router spindles can be broken down into full size and trim routers. The routers shown in Figures 2 and 3 are full size routers. Due to their weight and size, they are used on larger CNC machines. These are both 2-1/4 HP routers. They have plenty of power for most operations, and work well for cutting wood, plastics, and aluminum. Full size routers can handle tool shanks from 1/4” to 1/2” and with adapters or special collets, down to 1/8”. The routers shown in Figures 4 and 5 are trim routers. Most trim routers work just like their larger counterparts, but are smaller and produce less horse power. These routers are just under 1 HP. Trim routers are common on many small to medium CNC machines. Most can handle

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tool shanks of 1/4” or 1/8” with an adapter.

Figure 4

Figure 5

Rotary Tools There are dozens of rotary tools of all shapes and sizes. Most are meant to be held in your hand and are used to engrave, cut, grind, and drill various materials. Unlike routers, they are not meant for the larger tasks that routers can handle. Two rotary tools that represent most variations you will find at home centers or hobby shops can be seen in Figure 6. While they are well suited for handheld use, they are not suited for CNC use. They have slop in the bearings and tend to have too much runout to get an accurate cut. There are tools that fall into the rotary tool category but are better suited to CNC use. Let’s talk about three of them. The first is the Wecheer WE248 shown in Figure 7. This is the first rotary tool I attached to the KReduCNC that produced results that were accurate and repeatable. The tool has no slop and very little runout. It’s powered with an included AC adapter, and proved to be very easy to make a spindle mount as shown in Figure 8. I used this rotary tool, and while I was able to cut softer materials, I found it to be under-powered. It also has an auto shutoff if it senses too much load. I did find it worked very well for PCB (printed circuit board) work. After playing with the WE248 for about a week, I realized I was not pushing the KReduCNC as much as I could. It was time to look for a better suited spindle. I could probably get a trim router to work, but I would have to slow down the Z axis due to the weight. Having good luck with Proxxon products, I selected the rotary tool shown in Figure 9. It’s the Proxxon Micromot 50/E. It has much more power than the Wecheer, and I was able to cut deeper and faster. Its size also made it very easy to mount on the KReduCNC as shown in Figure 10. The 50/E worked much better than the WE248, but I still had the following issues: 1. It requires a special 12V power source. While I was able to make one, it does add some complexity to the build. 2. The speed control can bog down, as it has no feedback control. It can also shut down if pushed too hard. 3. I still wasn’t pushing the KReduCNC hard enough. While doing my research, I came across the Proxxon Micromot IBS/E shown in Figure 11. This is a rotary tool that costs almost as much as a full-sized router, so I was reluctant to take the plunge. Then, while cutting some softer material, the 50/E stalled out when it cut through the stock and hit the waste board. I ordered the Micromot IBS/E. Despite the $130 price tag, the IBS/E (Figure 11) is a

Figure 6 Figure 7

Figure 9 Figure 10

Figure 8

Figure 11

remarkable tool. It boasts a 1/8 HP motor, which is plenty for the KReduCNC. It is designed for continuous use and has a full electronic speed control with feedback. Its speed range is 5,000-20,000 RPM. I can honestly say it’s the smoothest rotary tool I have ever used. The motor in the IBS/E is the same used on the Proxxon MF70 (Figure 12) that I incorporated in a CNC conversion I did a while back. SERVO 02.2017

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Figure 13

Figure 12 Figure 17

Figure 18

Figure 14

Please note that I am using hex nuts with integrated washers. I find that these work better for me than separate hex nuts and lock washers. In addition to the hardware above, you will need the following components (also shown in Figure 13) to make the IBS/E mount: • IBS/E back plate • IBS/E upper mount clamp • IBS/E lower mount clamp Figure 15

Figure 16

Figure 20 Figure 19

Mounting the IBS/E To attach the IBS/E, you will need the following items that are shown in Figure 13: • Two #6-32 x 1” machine screws • Four #6-32 x 1-1/2” machine screws • Two #6-32 x 2” machine screws • Eight #6 washers • Eight #6-32 hex nuts • Eight #6 lock washers

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Step 1 Insert a washer onto each of the #6-32 x 1” machine screws, and slip it into each of the mount clamps as shown in Figure 14. Secure both screws with a #6-32 hex nut and lock washer as shown in Figure 15. Do not tighten the nuts, as you won’t be able to install the spindle later if you do. Step 2 Attach the lower mount clamp to the back plate using two #6-32 x 1-1/2” machine screws. Add a washer to the screw, then insert it into the front of the lower mount and through the holes in the back plate as in Figure 16. Secure with a #6 lock washer and #6-32 hex nut (Figure 17). Finger tighten only, as you will need to adjust the mount after the ISB/E is installed. Step 3 Using two #6-32 x 1-1/2” machines screws with #6 washers, attach the back plate to the Z plate as shown in Figure 18. Secure with two #6-32 hex nuts and lock washers. Finger tighten only. Step 4 Place a #6 washer on each of two #6-32 x 2” machine screws. Insert it into the front of the upper mount clamp and through the top holes on the back plate as in Figure 19. Secure with two #6-32 hex nuts and lock washers. Again, finger tighten only.

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Figure 22 Figure 24 Figure 23

Figure 21

Step 5 Insert a 1/8” calibration blank into the IBS/E (Figure 20). You may also use one of the small bits included with the IBS/E kit. Insert the ISB/E into the mounts (Figure 21). The mount was designed to hold the ISB/E with the front (knob) of the tool facing right or left as shown. This will allow you to access both the spindle lock and the speed knob. Tighten the spindle clamping nuts (1” machine screws in front) on both mount clamps. Tighten the nuts holding the lower mount clamp in place. Step 6 Place a small square on the table and move the spindle until the bit is up against the square as shown in Figure 22. If the bit is not fully against the edge of the square, twist the whole spindle mount assembly clockwise or counterclockwise until it is. Tighten the upper mount clamp nuts (Step 4) and the lower back plate nuts (Step 3). Step 7 Move the X axis to the left and place the square against the bit as in Figure 23. Check to see if the square is flat against the bit. Move the X axis to the right and place the square against the bit as shown in Figure 24. If the square does not mate with the length of the bit, you may need to adjust the upper shaft (Figure 25) forward or backward to correct this issue. Adjust one side, then the other as needed. Once adjusted, Figure 25 repeat this step until the square is flush with the bit on both sides of the CNC.

Conclusion This completes the spindle hookup. I will post the drawing files for the IBS/E spindle mount on my

support page for the KReduCNC. I will also post the drawing files for the Wecheer WE248. There are other spindle options that I have used with success on the KReduCNC. Figure 26 shows the spindle from a Foredom flex shaft. Since the heavy motor is mounted at the other end of a flex shaft, you can pack a great deal of cutting power at your disposal. It will accept 1/8” and 1/4” bits. While it uses the same mounts as the Wecheer WE248, the one shown in Figure 26 is a version that has a dust shoe that connects to a vacuum.

Cable Management I wrapped all my wires, cables, and cords with some split loom tubing (Figure 27). This protects the wires and cables, and gives your machine a better look. Next month, I will conclude this series by testing the spindle and milling a couple parts. Check out the video here showing when I made the first cuts of the IBS/E spindle: https://youtu.be/mMECVXXJcA8. SV For any questions or comments, please visit the SERVO Magazine forums at http://forum.nutsvolts.com /viewtopic.php?f=49&t=17408.

Figure 26

Figure 27

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Get Social with FaceBox: the Friendly HeadBot By Dave Prochnow Post comments on this section and find any associated files and/or downloads at www.servomagazine.com/index.php/magazine/ article/February2017_Red-Box-Robot-FaceBox.

If you were lucky enough to score one of SparkFun Electronics’ (sparkfun.com) limited edition Cyber Monday Redbox Robots (KIT-14062), then you found one of the best deals from the 2016 holiday season. On the other hand, if you were just a tad bit apprehensive about pushing the “Buy” button, you’re still in luck. Included within this article is a complete parts list for making your own Cyber Monday Redbox Robot, as well as instructions and code for building a sociable headbot. If it’s a social headbot, it just has to be named FaceBox.

N

ick Poole at SparkFun has done a great job documenting the construction and programming of a tail-dragging variant for the Redbox Robot kit. Inside his “Red Box Robot Hookup Guide,” you’ll find everything you would need to build a fairly sophisticated obstacle-avoiding Arduino-powered robot. We want to raise the bar just a teensy bit higher, however, and build a bot that rises head-and-shoulders above the rest. We want to build a tracking, flashing, and speaking robot. Yes, we’ll keep the same red-box ethos espoused by Nick, but rather

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than a robot crawling around the floor, ours will sit on a countertop.

Parts is Parts Like we mentioned in the opening, you can make your own kit with the following Parts List: • SparkFun RedStick • SparkFun Motor Driver — Dual TB6612FNG (1A) • Hook-up Wire — White (22 AWG) • Breadboard — Self-Adhesive (white) • 2x Break-away Headers — Straight

• 3x 1,500 mAh Alkaline Battery — AA • Battery Holder 3xAA with Cover and Switch • Mini Speaker — PC Mount 12 mm 2.048 kHz • Ultrasonic Sensor — HC-SR04 • Hobby Gearmotor — 200 RPM (one) • Wheel — 65 mm (rubber tire, one) • Really Bright LED — Red 10 mm • Double-sided Tape (to attach motors to the box) All of these items (except the tape) can be ordered from the SparkFun online catalog. Additionally,

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if you wish to build your FaceBox exactly like ours, you will need to order a mini breadboard for holding the 10 mm LED. While Nick instructs you to use adhesive tape for attaching the breadboard and motor to the red box, we opted for metal screw and nut fasteners. Size #256 hardware should work for holding everything in place (Figure 1). Granted, you could just mount the various parts on the red box and call your project done, but where’s the fun in that? When decorating your FaceBox, try to add a little flair to the facial features. Give it a personality that will match the little beeps and tones that will ultimately be “spoken” from the attached mini speaker (Figure 2). We also used this decorating step for adding a couple of slots that act as hidden wire channels — keeping all of the wiring inside the box instead of cluttering up the exterior (Figures 3 and 4). Once you’ve laid out the “face” for your FaceBox, the final challenge is installing the motor inside. Unlike the “stock” Redbox Robot, only one motor and one wheel are used for FaceBox. This motor is mounted inside one of the end flaps of the red box (Figure 5). Two screws will hold it in place, but its shaft must extend beyond the box’s outside. This mounting requirement means that some cardboard must be removed from inside the box. Furthermore, you must

Figure 2. Use screw and nut fasteners for attaching everything to the red box. Figure 1. A pretty face begins with a large breadboard.

Figure 4. Hidden slots and channels help to keep the wiring manageable.

ensure that the motor’s shaft rotates freely and easily outside of the box. Likewise, you must have ample clearance for the Figure 5. Preparing the box’s end flap for installing the motor.

Figure 3. The wiring “rat’s nest” is kept to the inside of the box.

shaft to hold the wheel securely in place. You don’t want a tipsy social HeadBot.

Wires and Wires and Wires When all of the hardware has SERVO 02.2017

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Figure 7. The speaker is held in place by a couple of solder dots on its pins inside the box.

Figure 6. The RedStick and motor driver are plugged into the larger breadboard.

been fixed into place, it’s time to add the major components: the SparkFun

RedStick, SparkFun TB6612FNG motor driver, HC-SR04 range finder (Note: While this printed circuit board [PCB] is red, it isn’t a SparkFun product), mini speaker, and 10 mm LED (Figure 6). Two of these items — the RedStick and the motor driver — require header pins to be soldered into place. Pro Tip: Snap off the required number of header pins and push them into your breadboard. Set the RedStick and/or motor driver PCB over the pins and solder them into place. The result is a perfectly aligned pin set that is guaranteed to be breadboard friendly.

Figure 8. All wiring is plugged into the RedStick and motor driver. Excess wire length is stuffed into a channel below the larger breadboard.

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RedStick Pin -> Battery + Battery Vcc 2 4 10 11 12 A4

Depending on how you designed your face, you can mount the components either on the breadboards (remember, we elected to use an optional mini breadboard, plus the larger breadboard included in the Parts List) or directly onto the cardboard box. Components mounted on the cardboard box tend to loosen and fall out. You can prevent this mishap by adding a couple of dots of solder to the part’s pins that are inside the box. In our configuration, we mounted the RedStick and motor driver on the larger breadboard, the 10 mm LED on the mini breadboard, and both the range finder and speaker on the cardboard box. A couple of tiny mounting holes on the “ears” of the HC-SR04 PCB enabled us to use screws and nuts to mount the range finder, whereas the speaker was mounted directly on the cardboard box with the aforementioned solder dots holding it in place (Figure 7). Wiring everything together is as simple as following Nick Poole’s SparkFun Hookup Guide. That is, up to a point. Naturally, our FaceBox only uses one motor, so our wiring connections are a little bit simpler. Additionally, we elected to pair both the LED and the speaker’s output control to the same pin. This enables FaceBox to blink and speak at the same time with a single pin write

Connection VM Motor Driver & Battery Pack GND Motor Driver & Battery Pack Vcc Motor Driver AIN1 Motor Driver AIN2 Motor Driver PWMA Motor Driver Trig Range Finder Echo Range Finder LED Anode & Speaker +

Table 1.

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control output signal. Our FaceBox wiring connections are shown in Table 1. Remember, you’ll also have to make various Vcc and GND connections for the HC-SR04 range finder, LED, and speaker. Furthermore, the STBY pin on the motor driver PCB must be connected to Vcc. Figure 8 shows the FaceBox RedStick and motor driver all wired up and ready for action.

Coded for Socializing After you’ve triple-checked your wiring, it’s time to upload the Arduino program to your FaceBox. You can download the code from the article link. During execution, this code causes the motor to rotate back and forth while scanning for objects with the range finder (Figure 9). If an object is detected closer than 80 cm, a sequence of “conversations” is triggered. This is a visual and audio greeting. Once the conversation is complete, FaceBox returns to scanning for objects. You can easily modify this Arduino program for meeting your social needs and requirements. For example, the range finder has a resolution between 2 cm to 4 m. Therefore, a hallway can easily be scanned. Likewise, the conversing abilities of FaceBox can be altered via Arduino Tone commands inside the code’s Whistle function. Eager roboticists can separate the LED flashing from the speaker output for producing a more varied human interaction. Just assign (and wire) the LED to pin A4 on the RedStick and connect the speaker to pin A2. Adjust your programming for handling both output pins (e.g., use a PinWrite command for flashing the LED). There is one caveat for FaceBox that might restrict your social interactions. The motor is a high current drain feature on this robot. As such, batteries can get used beyond their ability to move the motor — the range finder, LED, and speaker will continue to operate just fine, however.

Figure 9. FaceBox has a limited “lifespan” when running on batteries. Use a 5V USB power supply for extended socializing.

For example, the batteries included with the kit are woefully inadequate for powering the motor in the FaceBox configuration. Substituting highcapacity alkaline batteries will help prolong FaceBox’s motor operation. A better solution is a USB power supply. Just slip a USB female-male converter plug over the RedStick’s USB connector and add a 5V power supply to the converter plug. This modification will easily run the motor, but it does restrict your placement options for FaceBox. In other words, your social HeadBot will be tethered to a household power outlet. Regardless of how you power FaceBox, this is one social butterfly that you must set free ... free to meet and greet. Granted, this bot’s mingling manners leaves a lot to be desired, but it is a real conversationalist. Its gift of gab will quickly grab an audience. SV SERVO 02.2017

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Fat Shark Teleporter V5 Review

The Multi-Rotor Hobbyist Introduction FPV systems have existed for model aircraft for a while, but they have never experienced the popularity they have in the last few years. With the explosion of the multi-rotor hobby, a number of inexpensive products have come on the market that let you see and record the view from high in the sky. Drone race pilots have come to rely on FPV for flying long, winding, and tight tracks that are hidden from view. Watching some of the videos of these races (https://youtu.be/heBTmPy9IVY) can be disorienting, and even causes some people to feel nauseous until they become used to it. Your eyes are seeing a rapidly moving and accelerating environment, but your body (namely the fluid in your ears) is not sensing that acceleration. This disconnect confuses the brain and causes disorientation. This has been the plague of many video gamers over the years, but can be combatted by providing an outside frame of reference, increasing the field of view, or by using traditional motion sickness treatments. The two biggest advantages that come to mind when thinking about why you should spend money on a FPV system both involve vehicle orientation. We’ve all experienced the terror of not knowing which direction is forward on our drone when it was at the other end of the field. The different colored motor arms or lights can become hard to distinguish. After a little nudging of the controls, a calm and experienced pilot will quickly regain an understanding of the vehicle’s attitude and all is well again. With a FPV system, you are viewing the world from (generally) the forward direction of the vehicle, so that hazard is effectively eliminated. There is a risk that you could become lost if you don’t know your flying area well, but that’s where spotters and the FAA rules stating that you must stay within visual range of the craft become important. The second orientation problem is the loss of depth perception. We’re used to seeing with two eyes spaced a few inches apart. This stereo vision lets us park our cars, generally without going through the wall of the garage. With your quad so far away, it is possible to lose that good

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By John Leeman Post comments on this section and find any associated files and/or downloads at www.servomagazine.com/index.php/ magazine/article/February2017_MultiRotor Hobbyist_Fat-Shark-Teleporter-Review.

Several years ago, I rode in the copilot’s seat of a small Cessna circling over northwest Arkansas. The view was great and the experience of sitting right behind the propeller with a view of where we were headed was fantastic. It made riding in economy commercial airliners seem even more boring and cramped than it already did. As multirotor pilots, we can now have that experience with first person view (FPV) equipment that literally puts us in the pilot’s seat and immerses us in the experience of flying.

sense of depth perception. Fixed wing model flyers may think they are well inside an obstacle such as a telephone pole, only to be surprised and saddened when their plane hits the pole and falls to the ground in multiple pieces. A FPV system doesn’t really eliminate this problem, but it could aid you somewhat. Most FPV systems have one camera and transmit that single image feed down to your monitor or goggles. That single view means that by definition we cannot have true depth perception as it is not true stereo vision. It is useful for seeing if you are flying directly at that telephone pole, but the distance information will be fuzzy as it is just encoded in the size that the pole appears. Again, being a responsible pilot and having an observant spotter are keys to avoiding obstacles. This month, we’ll try out an inexpensive all-in-one FPV kit: the Fat Shark Teleporter V5 from getfpv.com. Jeff from getfpv.com was very helpful, and I ended up with the kit as well as an external monitor to attach to my remote, but more on that later.

FPV System Components Any FPV system has the same six basic components, with a few optional extras: the camera, transmitter, receiver, display, antenna, battery, and maybe an onscreen overlay. For a fully customized system, folks can mix and match components to get their ideal FPV rig. As a newbie to FPV, I decided to go with a kit that had all the components together and that would work out of the box. There’s plenty of time to learn and customize, but for

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levels of transmission power. Most of us use 2.4 GHz for the radio control system, so 5.8 GHz is the logical choice to avoid any interference. There are many systems on the market that will require an amateur radio license as they are operating at power levels or bands that the FCC (Federal Communications Commission) more Camera heavily regulates. There are two routes you can go Getting an amateur radio license for your camera: dedicated or feed is not difficult these days and probably through. Dedicated cameras are used something on your hobby to-do list only for piloting the vehicle, not for anyway. I recommend picking up the high quality video recording. After all, book The ARRL Ham Radio License we really don’t need full 1080p on a Manual (http://amzn.to/ 2frdBNl) 4” or smaller screen when flying, do and studying up for the multiplewe? Sure, it’d be nice, but it comes at choice test. You can also check out a significant cost and I wasn’t ready to Command Productions at dive in at that level — especially since I Figure 1: The camera that comes with the kit is very small and seems pretty well built. It www.licensetraining.com for a didn’t feel like it was a necessity. would have been nice if threaded inserts guaranteed study course. Our system Dedicated cameras are generally very were in the case as it would have simplified the mounting procedure significantly. (Figure 2) is certified to be FCC simple with a fixed focal length with a compliant, so a license is not needed, rather wide angle lens for a good view but I think you’ll find that having a license opens up doors of the surroundings. They are also much lighter and less to new aspects of the electronics and RC hobbies. power-hungry than high-resolution cameras. Many pilots have another high-resolution camera Receiver recording the flight but storing the data locally, not The receiver can be a stand-alone unit transmitting it to the ground. Some bypass or built into your choice of display. In our the second camera and take a video feed case, the goggles included with the kit and from their higher resolution camera (often a the separate screen have receivers built in. GoPro or similar) and send it to a standBuilt-in receivers are certainly convenient in alone transmitter. A setup such as this is terms of not having another bit of gear to indeed more expensive than the dedicated keep track of, worry about the connectors solution — especially the camera. on, etc., but they are not as flexible. An The other tricky part is that many external receiver may allow you to record people wanting to get amazing aerial videos the video and/or have several output types have their cameras mounted on a gimbal. If for connection to the display of your choice. the camera is not pointing in the same Some are even easily hooked into your direction all of the time, piloting can be ground station laptop so all of your piloting tricky. Think about driving your car in controls (telemetry, video, etc.) are on one reverse. The controls behave in a way you screen. For simple flying and even basic are not used to since the “forward” view recording, the built-in receivers are just fine. direction of the vehicle has changed. After looking around the Internet, it seems that Display most people either use feed through with Displays are personal preference mostly, the camera fixed, or have the high-quality and I think I need to spend more time with camera on a gimbal and fly with a standard goggle and TV-style displays before I decide definition video feed from a dedicated which I like best. The monitor style displays camera. The camera included with our kit are easily mounted to the top of your radio (Figure 1) is incredibly compact and looks controller and often have a built-in receiver rugged enough to withstand some hard Figure 2: The transmitter and power regulator provide an easy and battery. It is incredibly convenient to landings. way to send the video back just attach this to your remote, turn it on, without requiring us to tie into the main power distribution bus and start flying. I also like the fact that you Transmitter of the vehicle. Notice the small can look up from the screen and see the Transmitters are commonly available in enclosed helical antenna aircraft. The experience is not as immersive the 2.4 and 5.8 GHz bands with varying attached to the transmitter. getting started I wanted to give myself the best possible chance of having a good experience. I did some research into the components on the market and was amazed by how many options there are in price ranges to fit just about every budget.

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Figure 3: The “TV” type display screen has a collapsible sun shield. When folded flat, it is easy to stick a couple of these into your flight bag for onlookers or other crew members to use. The integrated battery, charger, and radio receiver make it very convenient.

Figure 4: The Fat Shark goggles are compact and easy to use. The volume and channel selection buttons are raised and easy to find with the headset on. The center button can be used to activate the head tracker mode.

as goggles and sometimes the glare on the screen can be a real problem. The displays also are small enough that you can pack a couple of extras to give to observers if they want to watch you fly (Figure 3). The alterative display type is a pair of FPV goggles. This is really like playing a virtual reality video game, except that it isn’t virtual. You really feel like you are riding along on the quad. There are goggles with advanced features that help move your camera gimbal by simply tilting your head. Some even have fans to keep the air inside cool and fresh. The goggles in our starter kit (Figure 4) are standard definition with a few bells and whistles, but plenty to decide if the goggle experience is the way you want to fly. Antenna Antennas are an often overlooked part of many systems. While RF engineering seems like (and mostly is some would argue) a form of magic, it is important. A good camera, transmitter, receiver, and monitor can be rendered useless by a poor choice of antenna.

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The classic whip or “rubber ducky” antenna is what we are used to seeing on our handheld radios, walkie-talkies, and many remote control transmitters. Sadly, these inexpensive antennas are Figure 5: Having a small battery for the FPV system not the best for FPV work. seemed to make sense, as I These simple designs are would prefer to keep the safety-critical flight systems sensitive to the orientation isolated from the toys like of the transmitter and cameras and other receiver; they work best transmitters. when the transmitting and receiving antenna are in the same orientation. Given that our quad’s orientation is changing and the mounting constraints may be difficult, this is generally not the ideal setup. The patch or helical antenna is a very long range design, but also very directional. Given the requirements that your aircraft remain in line-of-sight, these designs are unnecessary and impose the extra complication of needing the receiving antenna to track the vehicle — either manually or automatically. A circularly polarized antenna such as a clover leaf design is the most popular choice. Such antennas can be easily built or purchased, are compact, and are relatively insensitive to the orientation of the transmitter and receiver.

Battery You can run your FPV camera and transmitter from the main flight battery. In fact, many setups are capable of running off the balanced charge lead of your battery, including our kit. For the first several flights, I did this with no problems. Sure, there is some extra drain from the load of the transmitter, but I generally fly with giant batteries anyway, so it wasn’t a concern. I did notice some noise on the video signal though. After some research, I found out that it could be from the large and rapidly changing current demands on the main battery. I could put some kind of power filter in, but instead decided that it really wasn’t worth the trouble. I added a second and much smaller battery to power just the FPV gear. I chose a Turnigy 1,000 mAh 2S 20C LiPo Pack, but any 500-1,000 mAh battery should do (Figure 5).

On-screen Display Another possible addition to your FPV system is an onscreen display or overlay. This is similar to the heads-up displays in commercial and military aircraft. At a glance and through your line-of-sight, critical information such as

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altitude, heading, speed, etc., is displayed. There are several units available; some contain their own independent sensors; others interface with specific flight controllers. I would really like to add this functionality to my setup, but that’s an entirely separate article or maybe even a full-on build.

Installation Installing the Teleporter kit is a relatively simple process. We need to mount the camera on the airframe, attach it to the Figure 6: While special tools are available to power system, and install or install melt-in bushings, the chisel tipped configure the display or soldering iron does a good job. Just get everything in line and gently press the bushing goggles we will be using to into the plastic parts. Figure 8: I used zip ties to secure the transmitter view the feed. as I’ll probably be moving it between different Mounting the camera vehicles, and wanted an inexpensive and easy solution. could be done in a variety of ways, depending on your particular airframe. The easiest mounting method is to use a strip of double-stick tape on two clean and slightly roughened surfaces. I used this mounting method for my first tests of the system and it worked pretty well. After a couple of flights, the camera was dangling when I landed, however. Luckily, the wires stayed clear of the propellers, but I knew I wanted a more permanent solution anyway. There are a few approaches one could take here. Go to the hardware store and find some small preformed “L” brackets to use; buy a strip of metal flat stock and bend your own custom bracket in a vice; or 3D print a custom mount. Given that I just got my 3D printer back up and running after some upgrades, I decided to take that route. Figure 7: Installing the camera mount is pretty straightforward assuming there is a good place on your airframe. The ELEV-8 and HI whipped up a little bracket in OnShape that quad we built both have several mounting options. consisted of a “U” shaped bracket and a camera mounting bracket that fit snugly inside it. The camera is a to adjust the pan and tilt before tightening the hardware snap fit into the bracket. The bracket’s rotation is locked by (Figure 7). two 4-40 clamping screws. The STL files are available on After mounting the camera bracket on the airframe Thingiverse (www.thingiverse.com/thing:1903250) and (again with 4-40 hardware), I routed the cable and zip tied in the supplementary material at the article link. the transmitter into place (Figure 8). The transmitter and I printed with a rather coarse (0.27 mm) layer height camera are then simply powered by plugging the balanced and about 30% infill using PLA. Instead of depending on charge lead of the flight battery or dedicated FPV battery the screw threads in a plastic part holding up, I decided into the power regulator (Figure 9). that a threaded bushing would be more effective. There are For testing, I used both the 4.3” LM403 LCD FPV some wonderful heat-set bushings available from McMastermonitor (getfpv.com; item #4195) attached to my remote Carr in many sizes. transmitter and the Fat Shark Teleporter V5 goggles from I used my soldering iron to melt in a pair of the 4-40 the kit (getfpv.com; item #4484). The screen came with a sized bushings (Figure 6; P/N 93365A120), making sure little bracket that mounts to the back of it and clamps onto they did not protrude too far into the camera pocket and the handle of the RC transmitter (Figure 10). prevent the camera from fitting inside the bracket. The bracket is surprisingly solid, but I’m worried about After the bushings were in, I snapped the camera into the screen’s mounting point (Figure 11). One small screw place and assembled the bracket. This bracket should be seems like asking for something to shear off, but it hasn’t relatively easy to mount on most airframes and allows you SERVO 02.2017

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happened yet. The clamp part of the mount is fairly robust, but I would suggest replacing the screw with a thumbscrew to make tightening or removing the mount a tool-less operation (always nice when in the field). After leaving the screen plugged into a USB charger through its micro USB port, I was ready for a test. Opening the sun shade proved to be a challenge, and eventually required me to use a small common blade jeweler’s screwdriver. A bit of sanding on the catch will take care of the excessively strong positive lock if yours suffers the same issue. I turned the screen on and scanned through the channels until I found the camera. The picture looked pretty nice and the contrast on the screen was enough to be seen when outside. Next, it was time to try the goggles. The goggles have a small external battery pack that fits into a pocket on the headband (Figure Figure 9: The power regulator for the transmitter runs off the balanced charge lead on your flight or accessory battery. It has ports for 2S, 3S, or 4S batteries.

12). After plugging in the battery and turning on the goggles, a quick channel search found the signal. The screens inside the headset are tiny, but they do provide enough resolution for you to fly the aircraft. No glasses can fit under these goggles, but there are insert lenses available for those that need some optical compensation. A few notes of caution accompany the goggles. First off, never expose the part where your eyes go to direct sunlight (Figure 13). The lenses in the goggles will concentrate the light Figure 10: Mounting the screen to the transmitter was pretty easy, but onto the small screen I’d prefer a thumbscrew to adjust and quite literally burn a the clamping force on the transmitter bar. The sun shade is a hole in it, rendering the nice addition and really made a goggles useless. Also, difference when flying outdoors. pay attention to the battery charging instructions that come with the unit. Remember how much energy is stored in these lithium-ion batteries and treat them with care.

Use

Figure 11: The bracket mounts to the screen with a single small screw. While I haven’t had problems, I am a little nervous about what will happen in an accidental tumble off the workbench.

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Flying FPV takes some getting used to. I knew it would be a strange experience, but I don’t think I realized how strange. I spent Figure 12: The goggle battery pack fits into a pocket in the time flying from the headband. It was sometimes a bit tricky to keep it in there, screen attached to the but a set of Velcro™ cable ties can solve that problem easily. remote and with the goggles. I have to say that the screen is better for being able to quickly switch to looking at the aircraft, but the googles blew me away (Figure 14). It was a very immersive flight experience Figure 13: The eye cups do a great job of that didn’t leave me sealing you into the goggles and preventing any outside light from interfering. Do not let wondering about my sunlight shine in these lenses or damage to orientation or how much I the screens may result! was really drifting. It was a bit unnerving to not be able

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the aircraft such as shallow banks and to see if there was something above, wind drift that were not nearly as below, or beside me (see the Rules obvious from the ground. section), but with careful flying and knowing the layout of my field I did get used to it. One feature of the goggles that I discovered by accident is the simulated The FAA guidance on FPV flying gimbal mode. The camera has a was fuzzy at best for quite some time, relatively wide field of view. By but the rules are very clear now. As depressing the top button on the with unaided flight, the aircraft must be goggles for a few seconds, they will visible to the operator at all times. Let display a zoomed-in section of the me emphasize that again, line-of-sight entire camera image. The section you operation is a requirement — even are looking at depends on the when flying FPV. If the battery on your orientation of your head. Turn left, system fails, the feed goes out of right, etc., to change the view. It is sort range, or some other problem occurs, of like having the camera on a small you need to be able to pilot the aircraft virtual gimbal. Remember though, that back safely. if you are looking to your left, you are If you are flying with goggles or Figure 14: Using the goggles is an really just looking at the left side of the other viewing equipment that prevent immersive experience — even if you do look a little strange! wide-angle image, not necessarily to you from physically seeing the aircraft the real left of the quad. with your own eyes, you are required to Without proper gimbal mounting have a full-time spotter. The spotter or the camera having a spherical lens, must remain in visual contact with the it’s just not possible. This feature did aircraft and should be in constant make flying a little easier as I had a communication with the pilot about any more zoomed view of what’s ahead, hazards. but again required some adjustment. As we talked about above, you only For advanced setups with a gimballed get one vantage point with an FPV camera, these goggles can be set to system and can be unaware of hazards control the gimbal based on your head approaching from above, below, position. That sounds like a future behind, or to the sides of the vehicle. project to me! Remember, the FAA governs Flying from the screen attached to outdoor flight only; indoor flights are the remote was a much easier currently a free-for-all according to my transition (Figure 15), but I really found understanding, but remember, I am a myself mostly flying visually and looking geophysicist, not a lawyer. With all of at the screen occasionally. The sun your flights, remember to be a Figure 15: The screen was a nice way to shield worked very well to help keep combine visual and FPV flying, but was not responsible pilot and keep the hobby nearly as immersive as the goggles. When things visible when in the field, but in safe, protect people on the ground, and at higher altitudes, it was an easy way to some situations, it was still difficult to constantly be on the lookout for verify my orientation and get some see. It was useful to be able to look problems. spectacular views. down and get an idea of what was ahead in my given orientation, but the experience felt much less like being in the seat of that Cessna and much more like playing a video game. It’s amazing really. When I was a kid, none of this was The video quality was rough at times, but that’s what possible. Multi-rotor flying vehicles were only found in we expect from these lower resolution cameras. It was research labs. Now, anyone can own and fly one. With a certainly plenty to fly with, but not what I’d use as my few hundred dollars, we can add a FPV system and recording camera. There were occasional glitches or noise, experience life in the pilot’s seat. I can already imagine the but not enough to be a problem. Looking around on next iterations of this technology. YouTube, this seems to be perfectly normal for a flying feed. Will something like the now-defunct Google glass come I did notice that my normal flying space was very small along that allows us to watch the aircraft, view a video when I was getting started with FPV. I recommend finding feed, and see our critical parameters all in one go? Can we a very big open area with no obstructions while you are adapt to that much information and still make clear acclimating to first person flying. judgments quickly? I certainly think it’s possible and am It was also interesting to see the small movements of excited to see what happens next! SV

Rules

Closing Thoughts

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Twin Tweaks

by Bryce Woolley and Evan Woolley Go to www.servomagazine.com/index.php/magazine/article/ February2017_TwinTweaks_Junkyard-Robot-Warrior to comment on this article.

Junkyard Warrior

S

challenges ran the gamut, and the intrepid builders (many of them hobbyists and not professional engineers) would build everything from giant trebuchets capable of launching Mini Coopers to amphibious vehicles equipped with Archimedes screws to portable bridges. Sometimes the machines weren’t super effective, but the vast majority of the time they were. Throughout the builds, quirky animations showed how the teams were applying engineering principles to their junk. The show was a weekly reminder that you don’t necessarily need a lab full of high-end brand new equipment to make cool stuff. Plus, adding in a time constraint really put on the pressure for finding creative solutions that could be executed in a day. We credit Junkyard Wars (along with the original run of BattleBots™) as a major inspiration that got us to start building stuff too. Cathy Rogers, the creator of Scrapheap Challenge and Junkyard Wars, was herself inspired to make the show by a real life (and extremely high stakes) example of building something out of the spare parts laying around. On April 14, 1970, an oxygen tank exploded on the Apollo 13 lunar mission. The incident generated one of the most quotable (and misquoted) lines in all of space travel when astronaut Jack Swigert reported that “Houston, we’ve had a problem here.” They had a problem indeed. The exploded oxygen tank was essential to powering the command module, so the astronauts retreated to the lunar module as a kind of lifeboat. The junkyard wars moment arose because the lunar module was not equipped with enough lithium hydroxide (LiOH) canisters for removing carbon dioxide. The command module had its own LiOH canisters, but they were square shaped and the lunar module canister sockets were circular. Confronted with the problem of PROTOBOT HANGING OUT UNTIL ITS NEXT literally putting a square peg into a PROJECT. round hole, the astronauts

ERVO Magazine proudly proclaims that it is “for the robotics innovator,” and we think that’s quite apt. We love reading about all of the cool projects every month, covering everything from drones to animatronics to combat robots. More than just intellectually appreciating the cool stuff that other people are doing, we think SERVO inspires readers to go out and build something themselves. That’s certainly the case with us. We’re very fortunate to have access to a lot of the latest and greatest kits as SERVO’s resident Twin Tweakers, but every so often we’ll be left to our own devices. That’s when we can engage in hacking at its most elemental. Some of the most fun we’ve had is scavenging stuff from the garage to make something cool. That’s how we came up with our fighting printers from the August 2013 issue, and that’s pretty much how we ended up building our favorite prototyping platform, Protobot. What could we come up with this time, limited to scavenging from the garage and compressed to the timeframe of a weekend? We would have to find our inner junkyard warrior, roll up our sleeves, crank up the music, and find out.

Junk History Building cool stuff out of the junk you have laying around has a proud and colorful history. One of our favorite shows from back in the heyday when you could actually learn something on The Learning Channel was Junkyard Wars (the American title of the fantastic British series, Scrapheap Challenge). Our love of Junkyard Wars ran so deep that we actually auditioned for them and appeared on the kid’s version of Junkyard Wars in 2002 — Operation Junkyard (or OP/JY to those hip to the lingo). In Junkyard Wars, two teams had 10 hours in a junkyard to build something awesome, and the next day they would see whose creation was, in fact, the “awesome-ist.” The

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Twin brothers hack whatever’s put in front of them, then tell you about it.

improvised a device with the materials they had on board. The result was what they termed the Mailbox. Using materials from a space suit and various other fittings, they crafted a way to mate the square canisters to the round sockets. The junkyard wars moment was re-created in the 1995 film, Apollo 13 (which also contains the now ubiquitous misquote “Houston, we have a problem”). The teams in Junkyard SCAVENGED MOTORS IN ROBOT CENTRAL. Wars competed for bragging rights and a Protobot is our trophy made of junk — not quite the prize of not favorite prototyping suffocating/freezing to death in space, but still plenty cool platform, and we to inspire a generation of builders — ourselves included. have it hanging up in Robot Central, suspended from A HISTORIC PIECE OF SPRING STEEL. We admit that Robot Central isn’t just your everyday hooks in the ceiling garage. It’s seen over 15 years of competitive robot like how many normal folks would store a bike. We pulled building and many more years than that of car building. down the bot and determined that whatever mechanism We’ve got an unusual assortment of parts, but not we came up with could easily find a home on Protobot’s necessarily that unusual an assortment of tools. We have a spacious frame. drill press that came to us during our FIRST days as a We began scrounging around for parts to see what donation from an awesome team member (thanks Evan inspiration would strike. We first unearthed an old Heid!), a hydraulic press, and a chop saw, but other than Magmotor from our solar boat days. Our local water district that it’s pretty much hand tools. So, don’t worry if you sponsored a competition for high school students where we don’t have your own CNC machine capable of turning a built solar powered boats to run in sprints and endurance billet into a shiny smooth unibody frame. We don’t either, style races, and the Magmotor was used to power the and we get by just fine. propeller one year. Unfortunately, when we popped off the The first step in a weekend warrior scrapheap challenge gearbox, we were greeted with a kind of wet time capsule, type build is to find your inspiration. Unfortunately, we as lake water picked up from the competition over a decade didn’t have Robert Llewellyn and Cathy Rogers to announce ago came pouring out. Perhaps the motor could be revived, a challenge for us, or an exploded oxygen tank and the but that would be a project in and of itself that our selfnecessity of not suffocating on carbon dioxide to direct us. imposed time limit of a weekend would not allow. We had to come up with something on our own. We also had a fan motor from Bryce’s BMW 540i. The

Nuts and Volts and Bolts

PREPARING THE

PROD.

EYEBALLING THE

MOUNT.

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FEELING THE POTENTIAL. TEST

fan exploded one day on the freeway in Los Angeles, CA prompting a tense stay on the off ramp while waiting for the tow truck to arrive, lest the engine overheat like the creation of many a losing team on Junkyard Wars. We ended up replacing the fan and motor assembly in toto because you don’t just throw something away with an origin story as death defying as that. The fan motor itself is a little unusual in that it doesn’t have a traditional shaft. It has a flat flange type thing that would lock into the fan, and a large part of the fan casing actually spun around with the flange. We still had projectiles on the brain, and given our penchant for medieval weaponry (our 30 pound combat robot is called Twibill Trouble), our brains immediately focused on a more old-school way to throw stuff around than an air cannon: a catapult. Specifically, we were thinking of a mangonel. A mangonel is a catapult that works through torsion. Unlike a trebuchet — which depends on a falling counterweight — the mangonel relies on twisted ropes or springs. We thought that the fan motor could be used to twist a torsion spring. Another unusual aspect of the fan motor was that it had a three-wire lead with some funky connectors. It would

FIRING.

take a little thinking to determine how best to get it to work with the Victor speed controllers on Protobot, and as we were scratching our heads over this very problem we finally found our perfect inspiration staring us in the face. The walls of Robot Central serve as a sort of shrine to builds past, with various souvenirs we’ve collected watching over our new endeavors. We’ve got side panels from old FIRST robots (one signed by Dean Kamen), castoffs from our own combat robots, and a few parts from other combat robots — friend and foe. One of the more unique entries in the menagerie is a panel of thin spring steel from Agamemnon: one of the first bots built by combat robot greats, Team Delta and a competitor in Robot Wars 1996. Dan Danknick from Team Delta was one of the awesome mentors for our FIRST Team, and the panel from a classic combat bot has been one of the prized possessions of Robot Central for years. As we were thinking about medieval weaponry, the idea of a crossbow (or perhaps ballista, given the scale we were going for) did zip across our gray matter. Our concern was that we didn’t have the proper material for the bow of the crossbow — something flexible that could store and effectively release enough energy to fire a bolt with enough power to fight off hordes of sieging Vikings (or shambling zombies, to borrow from more current pop culture). However, a panel of thin spring steel would be just about perfect.

Siege the Day

BATTERY

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DONOR.

As with many engineering advances, the crossbow replaced human skill with mechanical reliability. Bows were essential to warfare in medieval times and even earlier during classical antiquity, but their effective use required years — often lifetimes — of training. The crossbow — invented in China around the 6th Century B.C. —

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gotten through your initial sketches, allowed even the relatively untrained to meticulously edited your CAD drawing, achieve decent accuracy and power with a mocked things up in cardboard or wood, bow. and then finally marked your metal parts, Overall, the design of a crossbow is you’ve probably measured many more fairly straightforward. The bow (a lath or times than that. That kind of patience and prod in crossbow parlance) is mounted attention to detail is a great skill, but so is perpendicularly on the stock. A bow string being able to estimate and eyeball things is used to pull back on the lath to store and rapidly prototype on-the-fly. energy, and is held by a trigger until the We totally understand that robotics user wants to fire the bolt. By freeing up experimenters might be hesitant to train both hands for aiming and without the their eyeballs on their new robotics kit or strain of having to hold the bow string RoboGames entry, so that’s why doing manually, the trigger mechanism turned your own personal scrapheap challenge is even the unskilled into deadly archers. such a great idea. The only way to hone Back in the day, the prod of the your estimating and eyeballing skills is to crossbow was a single piece of wood, just do it, and you’ll definitely mess up often yew or ash. Thinner prods more along the way. It’s an inevitable part of the efficiently released energy than thicker process, so it’s ideal to do it on the ones, so we thought the spring steel panel random robotic crossbow you’re making from Agamemnon would be a perfect out of scrap wood and aluminum instead update for our robotic crossbow. of your new heavyweight. Our weekend warfare tends to follow After all of our scavenging and the same pattern that you would see in sketching, we were approaching the end top-notch building shows like Mythbusters of our first build day without having built and Junkyard Wars. We develop the design HARVESTING THE BATTERY much of anything. Since the core of the through some initial drawings, focusing on CONNECTOR. robotic crossbow was our prod from the how we’re hoping to harness the powers Agamemnon panel, we decided to start of physics. Our initial sketches helped us with that. The panel was choc’ full of various holes where pinpoint the crux of this design: the trigger. We needed a bot guts had been mounted to the panel. There were way to remotely actuate our trigger, and it needed to be enough holes already there so that we wouldn’t have to strong enough to overcome the sheer force of the drawn drill any new ones, which we liked for a few reasons. First, bow string. we really weren’t looking forward to drilling a bunch of We tossed around ideas about making a nut, which is a holes in spring steel anyway because it’s a huge pain. specially designed cylindrical device that both holds the Second, we didn’t want to modify our prized piece of drawn bow string and allows for a quick release. Eventually, combat robotics history. we decided against re-inventing the wheel (or, in this case, We chopped up some pieces of diamond plate to make the nut) and thought to repurpose the pin pulling mechanism from our last foray into trigger design. The pin pulling design is a bit more similar to some of the earliest crossbows, which used a pin to push up the drawn bow string over the lip holding it in place. After some initial sketching and blocking out how we wanted the assembly to fit on Protobot, we started building. One of our favorite parts about a quick turnaround/fly by the seat of your pants/let’s make something cool just for fun builds is that they offer unique opportunities to practice certain skills. As any FIRST alum or large weight class RoboGames competitor can tell you, a lot of planning and measuring and doublechecking happens for expensive projects (even those on a compressed timetable). The adage might counsel you to measure PROTOBOT GETS AN UPGRADE. twice and cut once, but by the time you’ve SERVO 02.2017

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sieging Viking or two. Eager to get a sense of how much power our bow would have, we notched the end of a PVC pipe to make a quick and dirty crossbow bolt. We took the bot out to the shooting range (the backyard), pulled back, and released. The PVC bolt jumped upwards and fell right back down; sort of like a breaching whale, but much less graceful than that analogy would ever suggest. We were a bit discouraged, but we hadn’t put in a track or trigger yet. So, perhaps there was hope after all.

Cross My Bot, Hope to Fly WIRING

UP THE NEW BATTERY.

some brackets for our bow string. For the bow string, we pulled out some of our trusty bungees — a garage staple that we think most folks would have laying around. We picked up some of the holes already drilled in the spring steel (even thick diamond plate is a lot easier to drill than spring steel). We attached the spring steel prod to Protobot’s wooden upright by picking up a few more existing holes in the spring steel plate. Hat tip to Dan or whomever drilled all of those holes over 20 years ago. With the prod in place (using screws instead of the authentic medieval method of a whipcord bridle), we were ready to give the bow a test pull. We attached a bungee cord and tried to put ourselves in a medieval mindset. Releasing the bungee bow string appeared to release enough energy so that one might even hope to fend off a

LOCKED, BUT NOT LOADED

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We entered the garage on the second build day confident that we could get our robotic crossbow into good shape. We cranked up the music (because every build has to have a rocking soundtrack) and set about our work to the sounds of a mix ranging from the Gin Blossoms to Lacuna Coil. One of our first tasks was something that had come up in our testing from the day before. Protobot’s electronics haven’t changed much from the way they were when we first built it over a decade ago, and that included the original sealed lead acid batteries. Lo and behold, those batteries finally decided to conk out on us after years of faithful service. A good robotics prototyping platform needs a reliable power system, and we decided it was finally time to outfit Protobot with lithium polymer batteries. We ended up filching the battery from one of our more recent projects — the Agent 390 mini tank from the April 2016 Issue. The 14.8V battery pack used a Dean connector, and we didn’t happen to have any extras hiding in Robot Central. We were committed to finishing this project using only scavenged materials, so a trip to the hobby store was out of the question. We Frankensteined some of our other connectors together, figuring that copious amounts of electrical tape could cover our sins (especially since Protobot wouldn’t actually have to stand up to raiding Vikings). The new battery made Protobot as peppy as a young bot again, and by the time the new battery was in place we had devised most of our crossbow track and trigger. We crafted the track from spare wood, making a channel for our bolt to travel through. To tension the bow string and to mate with the trigger, we created a block that would help guide the bolt through the track and give our trigger pin a place to slide into. We ran a rope from our Fisher-Price motor powered winch mechanism through a pulley so that it aligned with our block when the bow string was tensioned. The tension held the pin in while it was loaded, and we just hoped the motor would be able to overcome the sheer force to pull it out. For our crossbow bolt, we scrounged up a few options

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including some wooden dowel rods and an actual bolt (well, a long piece of half inch thick all thread). We drove Protobot into place (this was a robotic crossbow after all), took aim, and fired. The motor pulled the trigger pin with ease. The bolt sailed down our track straight and true; the spring steel prod released its stored potential energy with ease and efficiency; and our makeshift bolt shot straight into our target with an audible thump. It was so cool we did it again and again, discovering that the long wooden dowel made the best bolt for accuracy and ALMOST A BULLSEYE! distance. All those Vikings and walkers better watch out. We think that scrounging up something cool from the garage is fun not only because it brings out our inner MacGyver, but also because it shows that you don’t necessarily need tons of fancy parts to turn that inspiration from SERVO into something tangible and something as frivolous as a robotic crossbow — your first awesome. However, there’s something even more thought after “how awesome was that” will most likely be important and intangible than that. When your project — “but if I do this and that, it will be even more awesome.” no matter how silly or off-the-wall — actually works, you’re Nothing beats the inspiration and excitement of actually filled with such a satisfying sense of accomplishment that is creating something. So, get out there and build! SV really hard to replicate. Special Thanks to Dan Danknick Once you make something that works — even

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a n d

g{xÇ Now

by Tom Carroll [email protected]

Building a Robot? Just Go for It! I have had several people talk to me at meetings or at the SRS Robothon about building a robot. Several had read some of my articles about how to design and plan a project, and were worried that they might need CAD software and a lot of computer programming and electronics knowledge. I always want to convince people who have the slightest inclination about building a robot to "just go for it." am convinced that most people who even think about building a robot probably already have the hardest skill needed: a basic mechanical aptitude. Usually, a mechanical background is followed by fundamental electrical knowledge. Toss in a basic understanding of microcontrollers and coding them, and you’re on your way. If a person is missing one or two of these skills, perhaps a friend or neighbor can provide some help until that person can build on their own. Just a small amount of these skills and the desire to learn more about robotics can turn into a build of a nice robot. The actual process of beginning the robot project and making mistakes along the way are by far the best way to learn how to build a robot. Reading robot books will help, but actual ‘hands-on’ experience is the best teacher. As a kid, after seeing the movie, “Tobor the Great” shown in Figure 1, I decided that I wanted to build a robot. Deep inside, I knew it was just a tall man in a robot suit, but I really

I

Figure 1. Tobor the Great from the 1954 movie of the same name.

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wanted to believe that Tobor was real. The young boy in the figure was the hero of the movie’s story. I had no goal for my robot-to-be and it wasn’t for educational purposes. There were no ‘how to’ books on robots and only a few articles about robots built by others. I just wanted a robot. No, I did not have any aspirations that it would clean my room or help me with my household chores. I just wanted a robot to sit in the corner of my room and look ‘cool.’ Before discussing my robot project, I would like to talk about a unique robot built from ‘scratch’ that inspired me as a kid before talking about my first robot.

Gismo the Great by Sherwood Fuehrer I had also seen an article in the Boy Scout Boy’s Life magazine back in 1956 called, “Gismo the Great” shown in Figure 2. It was built by 13 year old Sherwood Fuehrer from Rhode Island. Sherwood (Woody) got the idea from his older brother when he said, “Oh, Woody, why don’t you build a robot.” Woody found some 2x4s for the legs, an oil can for the head with flashlight bulbs for the eyes, and other parts shown in Figure 3. He used an old motor that he got from his dad to raise and lower the arms that were made from Erector set bars. He had collected many electronic parts, wire, and switches since his hobby was ham radio. The body was an empty five pound pretzel can and

Figure 2. Gismo built by Sherwood Fuehrer in 1954.

he used a transmission housing for the hips. He soon had the arms moving and a claw opened to grasp objects. The flashlight bulb eyes flashed and the head buzzed. A pilot light and a flashing heartbeat adorned the body. After many hours building the robot, Woody named him ‘Gismo’ which was the name of his science teacher’s dog. As Woody later wrote in Boy’s Life, “So that was that. Gismo was now ready to meet the public, but at that time, I had no idea how much of the public he was going to meet. I entered him in the Rhode Island State Science Fair, where he won a first

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Advances in robots and robotics over the years. Post comments on this article at www.servomagazine.com/index.php/magazine/article/ February2017_ThenandNow_Build-Robots.

grant. He made quite a hit. I rigged up an “Out to Lunch” sign that I pushed in his hand when I wanted a rest from operating him.” The Providence Journal featured a story on his creation. Then, the Associated Press and the United Press ran a picture. Soon Gismo was plastered all over the United States. Before the week was over, he had made a debut on two TV shows. According to Woody, “I became deluged with mail. Letters came from all over the United States — boys wanting plans and girls just wanting to be friendly.” Woody later wrote, “Soon his picture caught the attention of the Pretzel Institute. They offered me an expense-paid trip to New York City if Gismo would show an interest in pretzels. This came natural to Gismo since his body was once full of pretzels.” Woody and his mother traveled to New York and stayed at the Hotel Roosevelt. “Word soon got around the hotel that there was a robot in room 1820, and curious visitors started crowding the hall,” Woody commented. They appeared on the Today Show with Dave Garroway, and Gismo went around handing out pretzels. He later appeared on a children’s show on the top floor of the Empire State Building. There was a contest sponsored by Ford that Woody wanted to enter Gismo into and he realized that he needed a complete overhaul with improvements. “My first try at making Gismo walk ended in sad failure. I put rollers on his feet and was pushing him along when he suddenly tripped over a crack in the floor. He sure needed first aid! One arm and two wrists were broken, and his pretzelcan body was mashed beyond repair.” Gismo and Woody kept being invited to television shows and other

Figure 3. Woody working on his Gismo robot.

exhibitions. He continued to evolve the robot’s complexity with motordriven feet, better sound from the external wire recorder, lights, and all the ‘bells and whistles’ that he could think of for his famous creation. One of Woody’s final comments in the Boy’s Life article was about his aspirations for the future. “If you hadn’t guessed, I’ve got my career ideas set on being an electronics engineer,” he said. “I haven’t seen any recent articles about him but all the TV and news coverage that he received really describes just how much interest the general public had in robots in the 1950s.”

Cosmo: My Overweight Plywood Monster Robot As a kid after reading about Gismo, I said to myself, “Hey, if Woody could build a large robot, so could I.” The first one was too heavy to walk as it was made of 3/4” plywood. As much as I enjoyed photography as a kid, I cannot locate any photos of my robot and I can’t recall any that I took of the robot I named Cosmo. My dad had a nice woodworking shop, so I used a table saw to cut the large pieces of plywood. Most of my

metal work was done with hand tools such as a hacksaw or with a Craftsman drill press. Cosmo stood about my height and had a head composed of a section of rectangular heating duct. A coffee can served as his neck but it was his huge chest that made him so heavy. It was about 18 inches wide by 12 inches deep and 22 inches tall. Two five inch round metal ducts served as his legs. His feet were rectangular pieces of plywood with Tonka toy rubber tires mounted onto roller skate bases with the metal wheels replaced by the rubber tires. Two AC gearmotors were each connected to one back wheel on each foot. The red light bulb ‘eyes,’ the two wheel motors, and the loudspeaker mouth were connected to my remote control panel via several old TV antenna rotator four-conductor wires. The first time I tried running the single speed wheel motors, Cosmo took a dive to the floor of my second floor shop and scared my mom to death. Needless to say, I had to enlarge the wheel spacing foot size to keep him upright. My dad passed away just before I was to show him off, so his only demonstration was on Halloween night to hand out candy to the kids, though his hands and arms were yet to move. He was so heavy, and it was hard to separate him into two parts so I was never able to get him to my school to show other students. I started to change his chest into a metal can that I found and my brother gave me some DC motors to use for his arms, but I never got to finish him the way that I wanted. I learned some valuable pieces of advice from my early robot-building experiences. Start small and learn about robot building before you build larger ones. Don’t use thick plywood as a body material. Keep the center of gravity / body mass as low as SERVO 02.2017

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Figure 4. Tommy and Jimmy Carroll build Gismo 2BL's arms.

possible. Never use 115 VAC power for a robot’s motors, electronics, and lights. Use DC motors with variable speed control. I ended up building smaller robots that were cheaper to construct, and used relay logic and photo-resistive cells for autonomy.

Gismo2BL for Boys Life Magazine Thirty years later in 1987, my own three sons were in Boy Scouts and I was their scoutmaster. So, I asked them if they would like to build a robot. My twin sons (shown in Figure 4) liked the idea, so I asked them to figure out what they wanted and to

Figure 5. A Big Trak dual motor assembly in the base of the Gismo 2BL.

look around for ‘robot’ parts to build with. I wanted them to look around for items that they felt were suitable for a robot, not my ideas. They selected a small wastebasket as the robot’s body and asked me if they could have two of my surplus dual motors (shown in Figure 5) that came from a Milton Bradley Big Trak toy futuristic military vehicle. One set of motors was for the wheels and another for the arms. They had a Big Trak that my wife and I had given one of them for Christmas, but I also had several of the motors that I had purchased at a nearby surplus store.

The robot was wire controlled and used four D cells for the six volt power. I decided that the project would make a great article for Boy’s Life, so I contacted the magazine and they loved the idea. I wanted to call the robot Cosmo, but the magazine wanted the article to be a follow-up for their original piece. I took some photos of my sons as they built the robot and I helped them by cutting pipe ‘arms’ and bending some metal brackets. On a business trip to the Dallas area, I dropped off the completed robot at the Boy’s Life offices and they dolled the robot up for the cover photo shown in Figure 6. We named the new robot “Gismo 2BL” as the second in the series on ‘How to Build a Robot for Under $50.’ The article became the cover story for the February 1987 issue. Boy’s Life came up with a Gismo 3 shown in Figure 7 that was remotely controlled by fitting a ‘robot body’ trashcan on top of an RC toy truck chassis. I’m hoping a reader will design and build a Gismo 4 that is microcontroller controlled by a BASIC Stamp or Arduino and featured in Boys Life too (or here in the pages of SERVO).

Starting a Robot Building Project Figure 6. Gismo 2BL could be built for less than $50.

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Figure 7. Gismo 3 is built on an RC truck chassis.

I started this article by using three different early home-built from scratch

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robots as examples that almost anyone can build. As many of you may have discovered, building your ideal robot is not always an easy task. With determination, the process can evolve into a labor of love, but the beginnings can be a bit frustrating. I have stressed planning and the design process for building a robot in several previous articles. I still feel that process can work for most projects, but it is sometimes just fun to start collecting ‘things’ that look like robot parts until you have enough items to envision a completed machine. To eliminate the frustration factor, it is wise to sit down in front of your pile of parts and just sketch out your initial ideas of what functions that you want the completed robot to perform. Overall appearance and size of the robot is a secondary design criterion. You also need to realistically look at what resources that you might already have and what additional items you will need to buy. If you are lucky, your pile of parts may be all that you actually need to complete the robot. You also might want to examine the complexity of your initial design, what capabilities that you have, and what tasks you might want to have someone else do for you. Let’s say that you saw a great looking and performing robot in a demonstration and have decided to build something similar. You contacted the builder and went to his house and were amazed at his shop. He had a large drill press, a milling machine, a 12” x 36” metal lathe, a sheet metal shear and brake, and a MIG welder. You have a small table-top drill press, a cordless drill, and a nice assortment of hand tools. Hmmm. “Should I look around for a contract machine shop or pay the guy who has the nice shop to build a few things for me?” you ask yourself. “Or, can I just do the project with the tools I already have?” On the electrical and computer side of your prospective robot project, you look around and see that you have an Arduino that you’ve experimented with and a few ‘shields’ that act as motor controllers and

Figure 8. Charlie the Robot by Jim Hill.

sensor input devices. You also have an inexpensive digital multimeter, soldering equipment, and some electronic-type hand tools. You have basic computer, electronic, electrical, and mechanical skills. Can you build a nice robot with your basic skills and resources? Yes!

Jim Hill and Charlie I have written about Jim Hill before. He’s a friend of mine from the past and his amazing robot, Charlie is shown in Figure 8. Jim worked at a car dealership as a parts manager and had access to larger tools, but he built his robot entirely with hand tools such as an electric hand drill and hacksaws. Of course, it is certainly easier to make large holes in sheet metal stock with a fly-cutter or hole saw than to drill a bunch of small holes with a hand drill, and then saw and file the holes into a large hole, but the final result is the same. Don’t say, “If I only had ...” Instead, say “I have this and that, and I can build a robot!”

Linear Actuators on Charlie Act Like a Human’s Muscles Jim’s robot in 1983 was as complex as any experimenter’s robot

Figure 9. Jim Hill's Charlie graces the cover of the April 1984 issue of Popular Mechanics.

of today. Carefully crafted aluminum panels and internal structural aluminum beams made for a robust machine. When he began the project, the resulting design was driven by what parts he could find. He lived near the great surplus store in Pasadena that most of us robot builders called ‘home base:’ C&H Sales. Jim used aircraft linear flap actuators that he found at C&H Sales for Charlie’s arm joints. These moved the arms in much the same manner as our muscles, since gearmotors with a rotary output with sufficient torque and light weight are very hard to find in surplus markets. Instead of having heavy motors at the site of each joint, Jim used rotating flexible cables connected to car seat motors inside the robot’s chest to transfer the motor’s power to the arm joints. All of this was accomplished with basic hand tools and a hand drill. This is an excellent configuration for any potential builder of a large robot with arms to consider. I featured Jim and his robot in a cover story that I wrote for Popular Mechanics in April 1984 (Figure 9). I had some far greater reader feedback on Jim’s robot than the one I had built. It was Charlie’s SERVO 02.2017

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Figure 10. Dave Shinsel and Loki.

Figure 11. Sensors and control block diagram.

Figure 13. Dave Shinsel and his daughter, Amber control Crash to a $100K win. Figure 12. Loki and Alice.

personality that drew people to him.

Dave Shinsel’s Loki Built from Parts from Everywhere I first met Dave Shinsel in 2009 at a Portland Area Robotics Society (PARTS) meeting when he brought in his homemade robot, Loki (shown in Figure 10) to demonstrate to the gathered members. The robot’s name, Loki is from the Norse God of Mischief, and quite frankly, it does look a bit mischievous to me. The robot’s head, body, and arms are made completely from items that he found in all sorts of places, such as cheap flashlights and soup cans for the eyes. Dave told me, “I am always on the lookout for useful and interesting things that I can use in my robots. The shoulders of Loki are made from carpet protectors that go under a couch’s legs.”

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“Loki’s drive wheels are lawnmower wheels I picked up at the hardware store. His tail-wheel is made from two inline skate wheels I caught on sale from a sporting goods store. Trim around the robot is mostly door-edge molding from an auto parts store, as well as the decorative lighting on the sides of the robot. There are lots of interesting decorative lights at auto parts stores,” Dave had commented. Being a software engineer for Intel certainly was a plus when it came to integrating all the mechanical appendages and wheel motors, and an array of sensors to a microcontroller. The chart in Figure 11 is a simple block diagram of Loki’s sensors and controls. Dave now leads the robotics technology division in the New Technology Group at Intel. Combing through the Portland’s area surplus stores helped him locate high quality bearings for a dollar each to use for the elbow joints, as well as the blue shoulder brackets seen in

the figure. As time progressed, I saw Dave add another arm and change the robot’s grippers. The original left hand gripper had come from a drug store. Loki’s voice was from an iPod dock speaker in his neck. Dave found his robot’s side and front louvered grills on a trip to Home Depot. He very cleverly used a laptop as a display in the robot’s chest as well as the keyboard to program him in Visual C++, with a PIC based microcontroller using a CCS C compiler. Two simple Logitech clip-on computer cameras served as stereo eyes.

Dave’s Alice Robot

Dave built the robot he called Alice after Loki as a software test platform. Next to Loki in Figure 12, you can see the Microsoft Kinect sensors on Alice to the right, and added to Loki on the left. Alice has an LCD display on the mast below the Kinect and the base is the newer Kobuki platform used on the latest TurtleBot 2 — the original of which was developed by Melonee Wise at Willow Garage. A software engineer, Dave rapidly turned into a robot hardware engineer through his series of robots. Besides the Kinect that is used as a 3D camera sensor, Alice uses an Intel NUC computer and an Arduino Mega 2560. The robot and its computers ‘talk’ with the sensors and motor controls through a USB hub.

Dad/Daughter Team Win Robot Combat League Championship As an interesting bit of Dave’s exploits, he was invited to participate

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in the Robot Combat League. The SyFy Channel developed a unique robot contest called the Robot Combat League in early 2013, and constructed 12 eight foot battle robots for the 12 competing teams. With Dave’s popularity from news on his many robots, he and his daughter were selected as one of the teams with Dave as the ‘robo-tec’ and Amber as the ‘robo-jockey’ (Figure 13). Dave is seated at a computer control system and Amber is standing with an exo-skeleton motion control system strapped to her body. They were furnished with a robot named Crash shown in an orange protective skeleton in Figure 14. Notice the metal ‘pipes’ in the back of the two robots that contain power, hydraulic, and control lines, as well as provide stability for the robots from a fall. Dave and Amber did not start out as favorites with some failed bouts in the beginning, but rose to the challenge and in the end won the series and a $100,000 prize. (Not too bad for driving a robot built by someone else and having a blast doing so!) Between bouts, each team was

Figure 16. A cute little robot made from scraps.

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required to repair their robots, so extensive mechanical and robotics knowledge was required for each team’s repair people. The scene in Figure 15 shows their surprise as they were named winners of the $100K and the trophy in the center.

Final Thoughts I selected several different robots built from scrounged items by amateurs as examples Figure 14. Crash (in orange) meets Steel Cyclone in a of what anyone can build. Robot Combat League bout. These machines can be designed and constructed by high school kids or even elementary school students. They don’t have to be fancy motorized automatons with advanced microcontrollers and multi-axis arms. They can be a non-functional but extremely cute robot that can sit on your desk like the robot in Figure 16. You can then decide to give Figure 15. Dave and Amber are the winners of the Robot the robot motion by Combat League Championship. adding inexpensive Engineering, Mathematics) classes are servos and maybe changing the offered as early as elementary grades robot’s feet and ability to balance in many school systems. while walking, all while learning Yes, many great teaching tools about robotics. and associated robot kits are available Your inspiration can be from a from the advertisers in this magazine movie that you saw or to win an (such as the Parallax BoeBot series amazing prize in a contest. As a and their courses). parent or teacher, you can set a You can also expand a child’s child on a path to an exciting career creativity by promoting garage by encouraging the kid with a experimentation and basic tinkering budding interest in science and with things. Robotics does not have to computers to go just a little bit cost a lot. Anyone can build a robot. further and build a robot. SV STEM (Science, Technology, Front Panel Express .....................................7 Hitec .............................................................2 Maxbotix ....................................................39 M.E. Labs ...................................................28 Mikronauts .................................................59 PanaVise ....................................................59

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The new starting point for robotics

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