The Rules for Roboticists

[This piece originally appeared in The Absolute Beginner’s Guide to Building Robots]

Remember The Rules, that icky book written by those two insufferable women who nobody would want to date regardless of what relationship principles were or were not being applied? Well, I decided to dream up some rules of my own. No, they’re not things like “Never call a robot after the final assembly. Make it call you.” Or: “The way to a robot’s stomach is through its rear access panel.”  These “rules” represent the collective working wisdom of builders who’ve been bolting together bots for decades. The cyberneticist Gregory Bateson used to say: “Always tie your ideas with slipknots.” So these are not hard and fast rules, more like rules of thumb. Just a few things to consider as you build robots.

1. A roboticist is a generalist, a systems thinker.
One of the things that attracts a lot of people (me, for one) to robotics is that it involves the orchestration of many different disciplines. There are, obviously, specialists in the field — those who work only on AI control architectures, or robot locomotion, or whatever — but even they must keep the entire machine in mind. Most people who work in the field, and certainly all amateurs, have to have at least basic skills in numerous disciplines. As you get more into robotics, you’ll also find yourself spending a lot of time looking at humans and animals trying to figure out how they work. Oddly, trying to construct machine “creatures” gives one an even greater appreciation for the heavenly designs of nature, which brings us to…

2. A roboticist is a “deconstructionist”
As a robot builder, you’ll find yourself obsessively looking at the natural and built worlds and going: “Ah-ha! So that’s how it’s done.” Nothing will be safe as you take apart toys and machines that don’t work anymore (and some that still do), and find yourself playing with your food in a manner unsettling to others (“Cool, there’s the ligament attachments!”). But, for the love of all that’s civilized, leave the family pets alone!

Rumor has it that BEAM (and Wow Wee Toys) robot inventor Mark Tilden has been known to put all manner of bio-matter (chicken and other animal bones and bits) into his dishwasher so that he can clean them thoroughly for study of their mechanics, and one might even assume, incorporation into disturbing SRL-esque bio-mechs.

3. A roboticist knows how to K.I.S.S. it.
Actually not every robot builder knows this, but they should. K.I.S.S. stands for “Keep It  Simple, Stupid” and it’s a maxim recited (but frequently unheeded) in many design disciplines. Heed it in your robot building. Take time to plan your projects. Don’t just throw technology at a problem ‘cause you can. Use prototyping tech such as LEGO MINDSTORMS, VEX, and breadboarding to test out designs. Then try and figure out what you might not need and toss it. The simpler and more elegant your designs, the more likely your robot is to be stable and robust.

4. A roboticist must learn to think “outside the bot.”
Innovation comes from thinking differently, heading down the road less traveled. Don’t be afraid to take chances, to go in radical directions. Apply what I call Rodney Brooks’ Research Heuristic. Here’s how this works: In his book Flesh and Machines, Brooks reveals how he came upon many of his radical ideas regarding robots and AI: He would figure out what was so obvious to all of the other researchers that it wasn’t even on their radar, and then he’d put it on his. Essentially, Brooks would look at how everyone else was tackling a given problem, and what assumptions were so implicit to them that these assumptions were no longer being questioned. And he would question them. Don’t listen when people tell you that you can’t do something. Ignore your critics.

This is completely unrelated to robots, but it neatly illustrates our fourth rule. Many years ago, a friend of mine, a fabric artist, entered a beginner’s fabric weaving contest. She rented a small loom, learned how to weave, and decided to weave a seersucker blouse. Because she was new to weaving, she didn’t know that you “couldn’t” hand-weave seersucker (which is comprised of alternating puckered and smooth stripes). She had a devil of a time doing it, but she thought it was just because she was new to weaving. The judges were stunned. Needless to say, she won the contest, and the grand prize, a gorgeous room-sized Swedish loom that was the size of a small sailing vessel.

5. A roboticist is as much an artist as a scientist.
Find someone who’s done anything truly cutting-edge in science and technology, and chances are, he or she has a bit of an artist’s/poet’s soul. Independent engineer and self-proclaimed “high-tech nomad” Steven Roberts is often quoted as saying, “Art without engineering is dreaming. Engineering without art is calculating.”

6. A roboticist must be methodical and patient (like any scientist).

The pressure that many robot developers are under to deliver creations that live up to sci-fi-like expectations leads too many to attempt too much, too soon. Scientific development is measured, by its nature. Don’t be afraid to get one thing right rather than a bunch of things “sorta okay.” (Notice how we just contradicted rule number 4. What can we say? Rules are … well for those two ladies who wrote that book.)

7. A roboticist knows that neatness counts.

After you’ve built a few robots, you’ll quickly learn that the mechanics and (especially) the electronics can quickly become complicated, even in simple machines. There are usually wires sprouting everywhere, and trying to fit all of the parts inside your robot body, or on your robot platform, can become quite a challenge. You’ll learn that keeping everything neat and tidy will make a huge difference in the end. Use quick connectors when you can (for plugging and unplugging wires), use cable ties to bundle related wires together, and carefully plan (or revise) your design to maximize order and quick deconstruction/reconstruction of subsystems for easier troubleshooting. Color-code.

8. A roboticist must be a master of many trades.
As stated in rule number 1, a roboticist must be able to look at the big picture and know at least a little about a lot. He or she must have a working knowledge of materials sciences, structural and mechanical engineering, electrical engineering, and computer sciences. This may all sound intimidating to an absolute beginner, but knowing something about all of these areas of technology and science can actually be fun and exciting. And don’t let the big words trip you up. In plain English, these boil down to: building stuff (and knowing the right stuff to use), doing basic electronics, and knowing the ins and outs of microcontrollers and their software.

9. A roboticist should know his or her tools, materials, and processes.
You can have all the fancy “book learnin’” in the world, but if you don’t have a good working knowledge of robot building tools, building materials, and real-world construction techniques, you’re not going to be seeing robots scooting around your den anytime soon. The more you tinker, experiment, the more mad skills you’ll acquire — which leads us to…

10. A roboticist knows that you need to build early and build often.
Modern robot building technologies such as LEGO MINDSTORMS, VEX, iRobot’s iCreate, open source microcontrollers, prototyping boards, and other similar innovations (not to mention computer designing, simulation, and programming software) allow robot builders a tremendous amount of freedom to experiment and build on demand. Think of pre-PC writing tech (pens and paper, typewriters) versus a word processor (complete with spell- and grammar-checking, a built-in dictionary, Thesaurus, and so forth) and that gives you some idea of today’s robot tools versus those of a decade ago, even five years ago. Now you can have an idea for a new drive or sensor system, whatever, and have it built and tested within a few hours. If it doesn’t work, you can quickly disassemble and assemble something else. From this rapid prototyping can come truly innovative robot designs.

11. A roboticist should know when to come back later (A.K.A. “The Kenny Rogers Rule”)

When you’re building anything, especially something as complicated as a robot, the build can sometimes get ugly. If you try to force your way through, you can often dig yourself into an even deeper hole. So here’s what you do: “Put the soldering iron down. Step away from the steaming robot entrails!” You’ll be amazed at what an hour away, vegging in front of the TV, rolling around on the floor with the cat, or sleeping on your problem will do. It almost never fails. Here’s a corollary: The extent to which you don’t want to drop what you’re doing and take a break (“I know I can fix this, damn it!”), is inversely proportional to the extent to which you need a break. Why is it the Kenny Rogers Rule? Cause “you got to know when to hold, know when to fold ’em, know when to walk away…”

[“Heroes of the Robolution” trading card illos by Mark Frauenfelder, from Absolute Beginner’s Guide to Building Robots]

Other Robot Projects on Street Tech

Mouse Dissection 101

By Gareth Branwyn

This document was put together for the 2007 Bay Area Maker Faire(May 19, 20). If you’re coming to the Faire to take my Building Mousey the Junkbot Workshop, you can save some build time (giving you more time to enjoy the Faire) by bringing an already-prepared, recycled computer mouse. Here are the instructions you need to do that prep. We will have more dead mice at the Faire and we’ll have two parts bundles for sale: one to build “My Mousey the Car,” a non-robotic, much simpler, version of Mousey, and one to build the full Mousey the Junkbot, as seen in my book, the Absolute Beginner’s Guide to Building Robots, MAKE Vol. 2, and as a “special guest” on The Colbert Report!

Tools Needed:
Screw Driver(s) (likely small phillips head)
Dremel Tool (w/ cut-off wheel)
Shop Goggles or Safety Glasses (a must!)
Dust Mask (ditto)
Soldering Iron (full Mousey only)
De-solder Wick or De-soldering Pump (full Mousey only)

To create My Mousey the Car or Mousey the Junkbot, you first need an empty computer mouse case to house your cute little Frankenmouse creation. For the Car version (which includes little more than two DC motors, a power switch, and a 9V battery), you can use any mouse, mechanical or optical. For the full Mousey the Junkbot, with its LM386 brain, IR sensors, bump switch, and reverser circuit, you need an older, analog/mechanical mouse (you know, the kind with that always-grody rubber ball underneath). You likely have one of these in a junk drawer someplace.

In selecting your mouse, you want one that’s as symmetrical as possible and fairly roomy inside. You can use “lopsided” mice, such as the popular IntelliMouse from Microsoft, with the curved body. It’s just a trickier to build and to get the motors aligned and the weight balanced, so if you have a choice, choose symmetry.

You also want to do a little planning ahead to see how everything is going to fit. For the Car, this is no big deal. Any mouse should have plenty of space. For the robot version, this is a factor. Getting everything inside will be a challenge with a mouse of any size and design. Below is a rough layout for a typical arrangement for Mousey the Junkbot components. You’ll need to fit all of these inside your case (tho they don’t have to go in the same places). Unscrew the mouse halves. Many mice have screws under the little rubber glide pads, so check there if your attachment screws aren’t obvious.

With your proper mouse selected, you’re ready to remove everything that’s not needed inside. First, remove the printed circuit board (PCB). This is usually attached only by the scroll-wheel mount (if your mouse had a wheel), so snapping the wheel usually frees the board. Removed the cable, scroll-wheel assembly, and PCB. Save the PCB. You’ll need parts from it (if you’re building the full Mousey).

Now you should have nothing in the mouse but the encoder wheels and all of the plastic mounts for the various components and for attaching the two body halves. Get out your Dremel tool and a cut-off wheel. You should absolutely wear eye protection for this, and a paper filter mask. The plastic dust is nasty business.

If you’ve spec’d out where the parts will go, you’ll have some idea of what you can get away with leaving in. You’ll need a place in the top half for the toggle switch tail. If the screw post is in that vicinity, you’ll have to remove it. No biggie. You can hold Mousey together with a piece of tape when he’s finished. We recommend taking out everything that’s inside, just to give yourself as much room to work as possible.

When you’re done, a clean as a whistle bottom body half should look something like this:

Now you need to cut notches for your motors. If you’re doing this dissection in preparation for my workshop, you won’t have the two Solarbotics RM1A motors to use as your guide. You need to cut two tabs out of the sides of the mouse bottom. Make them at least 3/4” wide and all the way to the floor of the mouse bottom half. That should give you plenty of mounting room. Just so you know, the Solarbotics motors are approx 5/8” wide by just shy of ½” tall. We’ve found that placing the motors forward of the halfway mark (forward-to-back) is a good spot in terms of overall parts placement and robot performance. Here’s where we tend to mount ours:

Once you cut the motor notches, if you’re just building the Car, you’re done with the bottom half. The only other thing you have to do is drill a hole in the top half for the toggle switch. The photo below shows you the basic placement. You want to drill a hole ~1/4” wide.

If you’re building the full Mousey, the other thing that needs to be cut in the bottom half is the notch for the bump switch package. See the Motor Placement image above for the basic location. You’ll be using one of the button switches from the mouse as a bump sensor that’ll engage Mousey’s reverser circuit. You want the opening to be about 5/8” wide by about 3/8” high. The package itself is (likely) 1/2” wide by 1/4” tall. Don’t worry too much about these cuts. You can adjust them as you test-fit the motors and the switches.

If you’re building the full Mousey the Junkbot, you’ll also need to remove one button switch and the two infrared EMITTERS from the mouse’s printed circuit board. See the illustration below for the likely location of these components. Your PCB may vary slightly.

In this drawing, you are looking at a top-down view of the PCB, with the front end of the mouse at the top of the image. The encoder wheels aren’t used in this project, they’re just pointed out for orientation purposes. Once you’ve located your parts, get out your soldering iron and de-soldering tools. De-solder the pins on these components and bring them with you to the Faire, along with your prepped mouse halves.

BTW: You want to save (and bring) the two plastic pieces that make up the top surface of the two mouse buttons. They likely came apart as you eviscerated your mouse case. You can follow your own creativity as you build, but when I designed Mousey, one of the things I wanted to do was make it look as much like an un-altered mouse as possible. I’d seen some other robots in mouse cases, but the top of the mouse usually didn’t fit or it had been so altered it didn’t look mouse-like anymore. I wanted Mousey to look like your garden variety computer mouse that had somehow transformed itself into a robot, chewed off its own cord, and made a grand escape from its computer servitude. So, when the build is complete, you can glue the button parts back on your case to minimize the “damage” to the mouse formfactor.

BTW 2.0: You’ll also need to drill holes in the mouse top to snake the eyestalk sensor eyes through, but you should save that until you’ve installed everything else inside the case and know where the stalks should go.

* Mousey the Junkbot’s Webpage
* Free Mousey Project PDF from MAKE Vol. 2
* Mousebot Revisited, Additional Mousey Building Tips and Tricks on Instructables.
* My Soldering Tutorial
Information about the 2007 Bay Area Maker Faire

Images are from the Absolute Beginner’s Guide to Building Robots, Gareth Branwyn (Que). Illustrations by Mark Frauenfelder, Photos by Jay Townsend.

Mousey the Junkbot FAQ

By Gareth Branwyn

Here is the collected questions and answers I’ve processed, via email and online discussion, for the past several years related to Mousey the Junkbot, the light-seeking robot made from a computer mouse I featured in my book, Absolute Beginner’s Guide to Building Robots, and in the Mousey project in MAKE Vol. 2. If you have additional questions, feel free to ask them in the “Projects” topic of the Building Robots board in Shop Talk, our conferencing area.

Image of Make:Philly Mousebot Contest Entries, Courtesy Jef Wilkins.

Q: Are there other resources related to Mousey, besides this website? A: You betcha. Since the publication of my book, Absolute Beginner’s Guide to Building Robots, Mousey has taken off (so to speak). He seems to have his own career now. I wouldn’t be surprised if he didn’t soon have his own agent. As I write this, the original Mousey just showed up at my front door. He was coming back from a “showing” at a Chicago art museum, representing MAKE (in an exhibit about the history of DIY). Here are some of the other places you can find Mousey materials:

* He was in MAKE Vol. 2. He even made the cover! MAKE made the Mousey project article into a free PDF download. You can get it here. It’s everything you need to build our favorite mousebot. (Altho it does contain a slight error in the circuit design – keep reading for the fix.)

* After the MAKE issue came out, a builder, named Jake, put up a series of building tips called Mousebot Revisted. If you’re building Mousey, you should definitely check this out before starting your build.

* Mousey has quite the fanbase on Flickr. Various groups, such as Make:Philly, and individuals. have built their own mousebots and photo-documented their efforts. Search on “mousebot” and “mousey” in the MAKE pool to scoop up the Lion’s share of them.

Phillip Torrone’s Mouseys in the MAKE Flickr Pool.

* Make:Philly is an organization, inspired by MAKE magazine, that holds regular gatherings where members get together to build stuff. One of their meet-ups included a Mousey-building contest. One of the organizers, Josh Kopel, created a PDF page of hints, tips, and a re-done, corrected circuit digram. He also shows you how you can add a second bump switch, either a second whisker on the front, or a bumper in the back. Here’s a link to the PDF.

* Mousey the Junkbot: As seen on TV! On March 6th, Mark Frauenfelder, editor-in-chief of MAKE, and the illustrator for my book, was on The Colbert Report. He brought several projects from the magazine with him. One of them was a Mousey. Everything was going just swell, until Stephen Colbert drove Mousey off of the desk, where it broke into many pieces. Much hilarity ensued. After Mousey plummeted to his doom, Colbert quipped: “You built, not a robotic mouse, but a robotic lemming,” and looking offstage to his producer, sheepishly, he asked: “Is that in our budget? Can we replace robots?” The whole segment was really fun. You can see it and some follow-up blog discussion on MAKE’s blog.

Mousey the Junkbot on The Colbert Report, with Stephen Colbert and Make’s Mark Frauenfelder

Mousey started off life with a different name, Herbie. The original LM386-based circuit upon which Mousey was based was designed by Randy Sargent, then a student at MIT. It was originally designed as a line-follower (the two light sensors designed to keep themselves on either side of a black line on the floor – and therefore the bot following the line). Soon, builders modded this original design to follow light instead. Dave Hrynkiw of Solarbotics used a light-following Herbie in his book Junkbots, Bugbots and Bots on Wheels. Then, I created the Mousey the Junkbot version, encasing the Herbie circuit in a mouse case, and created the eyestalk light sensors. Now Solarbotics has further evolved the Herbie/Mousey robot family with Herbie the Mousebot, a wonderful kit that ingeniously uses three electrically=connected PCBs to create a mouse body, of the bio-rodentia variety. It has two whisker sets on the front and an optional clear LED on the back so you can get one Herbie to chase another. It’s a really fun kit to make. Here’s my review of it.

A gorgeous example of a Herbie robot, using Sargent’s original circuit, built here by Grant McKee. In an illustration in Make Vol. 2, this was identified as the original Herbie. It isn’t. I’ve never seen a photo of Herbie 1.0

BTW: While we’re looking into Mousey’s family tree, check out this rarity. It’s an image of a precursor to the Solarbotics’s Herbie the Mousebot kit.

And if you don’t think mousebots are supposed to be lively, check out this video of the kit beta in action.

Q: Are there any significant mistakes in the instructions given in your book or the MAKE article that I should know about before I get started? A: Yes, a couple . A builder, Gareth Adams, found a mistake in the subcircuit for adding sensitivty to Mousey’s light sensors. Wilf Ritger, creator of this circuit hack, pointed out on the Yahoo! BEAM group that the circuit as I have it in my book, and as it appeared in Dave’s Junkbots book (which is where I got it) is incorrect. The same mistake appears in the MAKE Vol. 2 version of the project. The current circuit diagram shows the correct wiring. PLEASE NOTE: This means that the breadboarding illos and photos in the book and on the site are also incorrect. Please refer to the circuit diagram when breadboarding. If you’ve already built Mousey with the incorrect connections, it shouldn’t be a big deal to reconnect them as shown. Thanks to Gareth (not me, the other one) for finding this bug. ALSO: In the book version of the circuit diagram, the orientation of the IR eye sensors got switched around in the illustration. If you just follow the diagram above, you should be okay. As far as I know, there are no other significant mistakes in the Mousey book chapter or the MAKE project. Any other issues, corrections or improvements are dealt with below.

Q: Can you post a Parts Lists and suggest places to buy the parts online?
A: Here is the complete parts lists for the Mousey project. Solarbotics has a parts bundle for Mousey. You can get it here. The lists below include the individual Solarbotics parts numbers and numbers for other suppliers (on the few items Solarbotics does not carry). Here are the suppliers’ Web addresses:

Mousey the Junkbot Bill of Materials

1 – Junked Computer Mouse (or new el cheapo one)
2 – Small DC motors (Solarbotics Part #RM1A)
1 – Double-Pole, Double-Throw (DP/DT) 5-volt Relay (SB Part #RE1)
1 – LM386 Audio Operational Amplifier (SB Part #LM386)
2 – Light Sensors (IR *Detectors* taken from mouse)
1 – SP/ST Toggle Switch (SB Part #SWT2)
1 – SP/ST Touch Switch (taken from mouse)
1 – 9-volt Battery Snap (SB Part#BHold9V)
1 – 9-volt Battery (the checkout line of your grocery store)
1 – 2N3904 or PN2222 NPN-Type Transistor (SB Part #TR2222)
1 – 1k-Ohm to 20k-Ohm Resistor (Range available from Solarbotics)
1 – 1k-Ohm Resistor (SB Part #R1.0K)
1 – 10uF to 100uF Electrolytic Capacitor (range available from Solarbotics)
2 – Spools of 22 to 24-guage stranded hook-up wire (one black, one red) (available at Radio Shack, or use salvaged wire)
4 – 6-1/2″ pieces of 22-guage solid hook-up wire (two red, two black) (available at Radio Shack, or salvaged)
1 – Wide Rubber Band
1 – Small piece of scrap plastic (about 1/4″ x 2-1/2″)
1 – Small piece of Velcro or two-way tape (optional)

Q: How come you’re supposed to use the Infrared emitters from the mouse as Mousey’s light-sensitive eyes? Why not the IR detectors?
A: The reason why we use the emitters and not the detectors from the mouse encoder wheels is that the IR detectors are designed to only turn on and off at a specific light level. The emitters, although they were designed to SEND infrared signals, will also respond to a wide spectrum of incoming light levels (just as any Light Emitting Diode, while it’s designed to emit light, is also sensitive to light). For the IR emitters, we do a number of things to make that light response more sensitive. First, we connect the Gain pins (1 and 8) on our LM386 Op-Amp chip, which boosts the signal strength, then we use “reverse biasing” (switching the positive and negative leads on the emitters) to pump up the signal even more, and then we add our sensitivity booster sub-circuit, which gives us another gain. All of this turns the lowly mouse IR emitters into reasonably light-sensitive robot eyes.

Q: I’m confused about the wiring on the light sensors. Why do you switch the wiring that you solder to the IR emitters?
A: This can be a little confusing (especially to those of us who are dyslexic). We thought the easiest way of handling the reverse biasing of the emitters was to first determine which pin is cathode (-) and which is anode (+), and then, solder the red (+) wire onto the CATHODE (-) side and the black (-) wire onto the ANODE (+) side. From here, you just treat the red and black wires as if they were positive and negative (even tho they’re actually reversed). Does that make sense? So what is happening here? By reversing the direction of the current flow through the emitter, it makes them more light sensitive.

Q: Can I move my “eyestalks” around or do they need to be positioned as they are in the project photographs?
A: You *can* bend the stalks apart and forwards and backwards. Part of the idea behind the eyestalk design is that you can mechanically “tune” the sensors by adjusting the position of the eyestalk wires. The fronts of the emitters (which have a little clear dome on their faces — think of them as pupils) should be facing the light source at all times.

Actually, you can also play around with any positioning, to see what sort of action you get by reflected light (from a shiny floor and a gaze that’s turned downward, for instance). But try such experiments only after you’ve got Mousey working properly with eyes front n’ center.

Q: So, LEDs can act as light sensors? That blows my mind.
A: All LEDs have photoconductive properties, if you reverse bias them (swap anode and cathode). Thing is, conductivity is not that high except under very bright conditions, so for practical use in a project like Mousey, IR LEDs work best, or obviously, a proper photodiode, photoresistor, or our mouse IR emitters (which are actually IR phototransistors).

Here’s an excerpt from the website about the light sensitivity of FLEDs (Flashing LEDs):

“Ben’s use of this circuit for a photopopper takes advantage of an interesting feature of FLEDs — they are photo-sensitive. In particular, light shining on a FLED causes that FLED’s SE to be inhibited (to perform more poorly). So if you’re building a phototropic FLED -based BEAMbot, you may have problems in bright light (both SEs in your ‘bot are being inhibited, so neither side of your ‘bot wants to fire) — you can address this by partially shielding your FLEDs with heat-shrink tubing, or some paint (be careful here, you’re trying to give your ‘bot sunglasses, not blinders). Meanwhile, if you’re using a FLED-based SE on a non-phototrope, you’ll want to completely cover the FLED (with heat-shrink tubing, or black electrical tape, or dark paint…).”

Q: I’m confused by the Mousey circuit diagram in your book, Absolute Beginner’s Guide to Building Robots. It shows that the cathodes of the IR emitters connect to pins 2 and 3 on the LM386 chip (instead of anodes, the black wires). What’s correct?
A: Crap! I can’t believe I didn’t notice that mistake in the book’s artwork. Somehow it got switched on the art. I can’t believe I didn’t notice this during editing. Here’s a link to the corrected diagram.

Here’s what I’m putting in the Bug Report:

Mistake in Circuit Diagram!: The Mousey Circuit Diagram in the book and the one on this website has a mistake in the emitter eye hookups. Somehow the bevel on the IR emitter packages got switched and we didn’t notice during editing. The leads on the emitters aren’t labeled, but because the bevel indicates the cathode (-) side, it looks like you’re supposed to hook the cathodes to pins 2 and 3 on the op-amp chip and the anodes (+) to power. Oh contraire! You want to hook the anode (+) sides to pins 2 and 3. It gets confusing because of the whole “reverse biasing” technique used here (running power through the emitters in reverse to make them more photoconductive). Just remember that you want the negative emitter leads to go to power and the positive leads to go to the pin 2 and 3 inputs (it’s counterintuitive, but that’s what you do). In the book, we recommended soldering a red wire onto the cathode leads on each emitter and a black wire to the anodes, and then just treating the wires normally (red wires plug into power, blacks into the chips input pins). Don’t know if this helps or confuses matters. Thanks to builder “Mousey Fan” for catching this error. Sorry about the confusion. Barbie sez: “Building robots is hard!”

Q: I love that illustration (of the circuit diagram) and the illustrations in your book. Who did them?
A: Mark Frauenfelder, of Boing Boing fame. And yeah, he did such a nice job, on all the illos, but especially that one and the servo hacking diagram from Chapter 7 (and, of course, the trading cards, which we hope to one day put up on the site). We budgeted all the illos at an hour a piece, but the servo hack image took Mark like six hours. It’s so hard doing a technical book like this and trying to make the images both attractive, easy to understand, and accurate. On many of ’em, I would do sketches, we’d scan them in, Blake (my son) would add stuff, clean up, label parts, etc., we’d send them to Mark, he’d draw, send back, we’d send them back with changes, etc. Maddening, and time-consuming. Given all that, I think they turned out really well. And then there was the photography and the Photoshop tweaking… Have
thanked Jay yet? Jay Townsend was the photographer. He did an amazing job too.

Q: Can you offer some advice on speed control for Mousey? I’ve built the circuit and can see the motors spinning very fast speed. I am afraid that when I put everything together my Mousey will be dashing around out of control.
A: The easiest thing to do is to just change the contact profile of the “wheels,” in other words; use a steeper angle on the motor mounting such that LESS of the gear/wheel comes in contact with the ground. You can also use a tire material with a slicker surface (rather than rubber) for the wheels which will “waste” some of the excessive torque.

It IS true that Mousey is extremely lively. I like this about it. Both the walker project and this one have a very biological feel to them. The walker has a persistence that’s very bug-like, and Mousey acts very jumpy and nervous like a bio-mouse. You want to try to achieve that balance where it’s right on the verge of chaotic. If I built mine over again, I would make the angle a bit steeper to reduce some of the traction.

Also keep in mind that the motors just sitting there tethered to the breadboard are much livelier than they are once they’re carrying the full weight of the mouse case, the 9V battery, the relay, the switches, and everything else. You can get an idea for how the motors will behave in the bot by using poster putty to temporarily affix them to the notches you cut in the mouse case bottom at different test angles (I talked about this in the book). Also temp. fix the battery and just toss all of the other parts in the case as well. Hook the motor wires between a switch and the battery, flip it on, and then try to grab the switch again to turn “this crazy thing off!,” as Mousey takes off like a bat outta hell. I did this when I first got these motors, to make sure they were appropriate. I put everything in the mouse (except, of course, the mouse case top).

I’ve gotten a lot of email from builders who find the Mousey too speedy, making it feel more like a demo-derby racer than a photovoric robot. So, we’ve done some testing on various ways of possibily slowing our mechano-mouse down. We tried adding resistance to the circuit — in series with the motors and on the chip’s power pin. Neither of these worked. Adding resistance in this way seems to screw with the op-amp chip’s ability to do its job (which is to dynamically equalize its output to the two motors). There may be some other way to re-design the circuit to add resistance (and therefore slow down motor RPMs), but I don’t have the time nor the inclination to go this route. The next thought we had was to tweak the “tires,” experimenting with different materials that would change how the rubber meets the road (so to speak). On the original Mousey, we used LEGO Mindstorms corragated plastic tubing. This stuff seemed fairly slick, but we wanted to try something even slicker. Before doing this, my bot-building assistant Jesse Hurdus tried making some “thick” rubber tires from rubber bands. Instead of just using one thickness of rubber band (as I suggested in the book), he wrapped the band around three or four times. It seems counter-intuitive (you’d think these tires would provide even greater traction and speed), but these bigger rubber tires seem to do the trick. They slow the vehicle down to an extent that the feedback loop between light/sensors/chip/motors is more effective. We also made the angle of the motors steeper, as was mentioned in an earlier post. The problem here is that, unlike Herbie versions of this bot design, which usually don’t have cases, with Mousey, you’re constrained by the lid of the mouse case when altering the motor angle. We made ours as steep as possible while still allowing the top to go on. We recommend you do the same. You can also go in the other direction and make the motors relatively flat on the case bottom. This works well if you use actual tires on the wheels, which a lot of builders do. We’ve seen builder make four-wheel Mousey’s (see photo at the beginning of this FAQ) with one passive axle and one powered. We recommend using the poster putty option and experimenting.

Q: I don’t have breadboarding gear. Can’t I just go ahead and build the robot. There aren’t that many parts. Could that much really go wrong?
A: Breadboarding is an essential part of electronics. A board and a jumper kit don’t cost that much. By breadboarding, you’re guaranteeing that all of the components are working and you’re verifying that the circuit design is correct and that you’ve interpreted it correctly. If you then assemble/solder up the project and it doesn’t work properly, you know that it’s not the circuit design itself or any of the constituent components. This makes troubleshooting a whole lot easier. So, everybody reading this, PLEASE, for the love of all that’s mechanical and brought to life by frisky electrons: breadboard, breadboard, breadboard! It’s amazing how much email I’m getting from builders with problems that stem from skipping this crucial step.

Q: I have the Mousey circuit working, but the LM386 chip is getting really hot, so hot, touching it gave me a small blister. Is this normal?
A: In a word: No. You must have been a short circuit someplace. The chip (or none of the other components) should get what would be described as “hot,” warm maybe, but not THAT warm. Look carefully at all of your wire connections and solder joins and look for crossed wires or bridges of solder that might be shorting the circuit.

Q: You claim this is a beginner’s robot project, and it’s in a book for “Absolute Beginners.” The soldering seems kind of hard and you have to buy breadboarding stuff, a multimeter and a lot of other high-priced tools. How can this be considered “beginner”?
A: I’m getting a lot of email from people complaining that this and the other projects in my book are too hard for a beginner. It’s ROBOTS, people! No real robot project is going to be easy. And these are scratch-built robots. When I ask these folks if they’ve built any of the kits first that I review and recommend in the book or done the soldering practice I recommend, they ALL say no. If you are a beginner and you jump in trying to learn soldering and robot building with one of these projects, it is do-able, and it’ll be quite the learning experience, but it will also not be without some genuine frustrations. I guess it’ll separate the true bot builders from the wannabes ’cause you’ll need patience and persistance, two qualities that a robot engineer needs in large quantities. But that said, I do recommend that people get their skill set down and some easier kits under their belts before tackling the projects. And as to the “expensive tools,” you’ll need all of this stuff if you plan to build any other bots or other electronics projects, and most of it is NOT expensive. The most expensive tool is the Digital Multimedia and you can even get a really respectable one of those inexpensively if you look for sales or buy one on eBay.

BTW, builders: When you buy parts, always get extras of components that are cheap. These IC chips, caps, resistors, relays are all inexpensive so get more than you need in case you blow any or they don’t work to spec.

Q: I did not want to wait for the motors from Solorbotics, so I went to Radio Shack and got some motors, the smallest ones they had. I want to slow Mousey down by attaching a large gear to do some gearing down affect, but I can not find a gear to match the teeth. Any help would be greatly appreciated.
A: The motors you got are probably the Mabuchi 1.5-3V models. Did they cost like US$2.99? Those are surprisingly great motors for the price. If I’m not mistaken, they’re used in the gearmotors for the WowWee Robosapien. Designer Mark Tilden has used these motors before, in the B.I.O.-Bugs and the Beastland Dragons (his two previous bot projects with WowWee).

For this particular project, however, they have some problems, tho. They EAT batteries. Much less power-efficient than the Solarbotics RM1 (which is also a Mabuchi, BTW). They’re also a lot heavier. Using two of these motors would nearly equal the weight of three of the RM1s. This might not be such a bad thing in terms of slowing your bot down. I think they’re also slower than the RM1s, which again, may not be such a bad thing in this instance. This may all add up to mean that, using these motors, you don’t have to gear down ’cause these other factors increase the mechanical resistance of the overall bot. The biggest problem is that…well…they’re big. More case-cutting, more fitting, more trouble getting the lid on the case. Then you’ve got gears and gear attachments/housings to consider. We specifically chose this motor because it fit the weight, power, and size constraints of this application. Improvise with this in mind.

Q: The LM386 chip has only 1 output on pin 5 controlling the speed of 2 motors independently that are on the same line. How is this possible? Am I missing something?
A: This LM386 chip is designed as an audio amplifier. It’s supposed to compare two input values and amplify the difference. It doesn’t matter what that difference is, just so long as there is one. It sends the amplified signal to the output pin. As the chip “struggles” to equalize the difference in the inputs, it changes the power on the output pin. It is this power fluctuation that is used to “steer” the motors based on the changing values of the two light-driven inputs.

The LM386/Mousey circuit uses a split-power output, meaning that if we have two power draws on the line, which we do, it will attempt to split the power needs evenly. But if we have uneven input, as when one “eye” is receiving more light than the other, the output reflects that in more power going to one motor than the other. These power fluctuations and then equalizations (when the two eyes are getting equal amounts of light input) allow Mousey to steer towards a light source.

This is an amazing little chip for what it can do. I was describing the circuit to a geek friend last night and he was in awe of the fact that you can make a “real” robot (read: one that has a true sensor-brain-actuator chain) out of something as lowly as an el cheapo chip designed to make speakerphones speak and analog modems go squeek-SKWACK-shsssssh, etc. I’m in awe of folks like Randy Sargent of MIT (who created the original Herbie circuit), Mark Tilden, and others who can create these minimalist robot brains out of lowly analog components.

BTW: has a nice library of datasheets for components used in BEAM (and BEAM-related) robots. Included here is the LM386 sheet:

Q: Are there any alternatives for the LM386 chip?
A: I know of no Herbie-circuit hacks using other op-amps. I’ve seen a similar photovore built from the venerable 555 chip, but I haven’t built one.

Grant McKee’s adorable Herbie built on a 555 timer chip

Q: I have read your explanation of how the LM386 chip works and I still don’t get it. Can you elaborate?
A: Okay. I’ll try. When the light value is the same (across both inputs), both motors receive equal power and steer the robot directly towards the light source. If one sensor is getting more light, it will split the difference to the power output. So, with a 9v battery, when light is hitting the eyes equally, both motors will each feed off of 4.5v and spin at the same rate. If the input becomes unbalanced, the voltage on the pin might rise to 6v, so one motor will have 6 volts to draw on, but the other will only have 3 available, turning that motor about half as slow. But the chip wants the values to be equal, so it will react by changing the power levels as the robot moves (as it amplifies and outputs the difference between the two inputs), always trying to lock onto an input of equal value on both input pins (steering the bot towards the light in the process).

Q: What do I need to know about resistor wattage ratings? I see that some are rated 1/4-watt, some are 1/2-watt, even 1/8-watt.
A: 1/4-watt is most common for these types of low-volt/low amp circuits. 1/8-watt resistors can also be used. This rating refers to the number of watts a resistor can safely dissipate, as heat, before it fails, fries, blows up, etc. 1/4-watt resistors are more than adequate for this circuit and readily available at retailers like Radio Shack.

Q: Why is a 5V relay used if the battery is 9V?
A: The coil on the 5V relay is activated at 5V, but it’s rated for much higher voltages (I think up to 24 or 30VDC on the contacts, don’t know the upper limit on the coil itself). The 5v relay is used because it’s a ubiquitous component found in many low-power electromechanical switching applications (such as our humble little circuit).

Q: I have a button switch not from a mouse that I want to use for the bump switch. How can I tell which of the three terminals on the switch I should use?
A: Ah. Good question, and a good opportunity to address some I didn’t in the book: selecting switches. Switches of this type (a button switch with three pins) are frequently marked on their case (or “package”). The print may be tiny. If it is marked, it will likely say “NO,” “C” and “NC.” These stand for “Normally Open,” “Common,” and “Normally Close.” If they are marked, you want to connect your circuit to the “C” and to “NC.” Normally Open simply means that the switch is open (i.e, off” when the switch is NOT depressed. A Normally Closed switch would power the circuit until the switch was triggered. Not good in our case.

If your switch package is not labeled, no biggie. Just set your multimeter to volts and attach your probes to two of the terminals (the center one will assuredly be Common). When you get juice flowing through the terminals with the switch in one of the On positions (facing away from Common), that’s your NO terminal and the one you want to use.

How-To: Build BEAM Vibrobots

In the current issue of MAKE (Vol. 8), I have a piece on Pummers, a type of solar-powered robotic plant life. I’ve known about Pummers for years, but my inspiration for doing the MAKE piece was finding Zach Debord’s gorgeous Pummer set on Flickr. Being an artist and designer, Zach understands the value of making miniature robots that are as beautiful as they are functional. Mark Tilden, the “Big God” of BEAM robotics, has a wonderful adage that a human is a way that a robot makes another robot. One “evolutionary strategy” here is centered on aesthetics. Aesthetics drive interest. The Pummer piece is a prime example. I saw Zach’s bots, I was wowed by their beautiful designs, and wanted others to see them. The piece got published, and now, if you search on Pummer in the MAKE Flickr pool, you see other people are making them. The robots are replicating themselves.

In the realm of behavior-based robotics, BEAM, bio-mimics, and other bottom-up, bug-brained approaches to robotic design, nearly every conceivable form of motility has been tried. There are bots on wheels, two-, four-, six-, eight-legged bots, bots with whegs (wheel/leg crossbreeds), snakebots, spinnerbots, swimmers, fliers, climbers. You name it. One of the less documented types of robotic motility is found in the Vibrobot, a type of robot that gets around by shimmying, shaking, and scooting. It’s not the most graceful or accurate way to explore the world, but it’s very easy to build a Vibrobot and they’re really fun (and funny) to watch.

The key to Vibrobot movement is a motor (or motors) that employs an unbalanced weight. Pager and other motors used to create vibration alerts in consumer electronics use this technique. As the motor shaft spins, the weight on the shaft, being off-kilter, makes the motor, and therefore the entire pager, vibrate. Hook such a motor up to a little robo-critter with four fixed legs, and when the motor fires and the weight starts spinning, the bot will skitter across the floor. That’s all there is to it. Since the legs don’t need to be articulated or driven, there are few mechanical challenges in building a Vibrobot. The power circuit is very simple too. The simplicity of the mechanics and electronics frees you up to put more effort into making the bots look incredibly cool. It’s no wonder then that, as with Pummers, Zach has built an amazing menagerie of Vibrobots. We asked him to tells us how he goes about building these wacky little robo-critters.

Here’s a call-out image that details the parts used in a basic Vibrobot (the Solar Engine circuit is detailed in the diagram below).

As you can see, it’s all fairly simple. This Vibrobot uses the FLED (as in “Flashing LED”) version of a Type 1 Voltage-Triggered Solar Engine. This type of common BEAM power circuit was discussed in my “Beginner’s Guide to BEAM” and the “Two BEAMBots” projects in MAKE Vol. 6. This is the same FLED Type 1 SE used in Zach’s Twin-Engine Solarroller we wrote about on Street Tech a few months back. In that piece, tI quote from a reasonably clear explanation of how a FLED-driven voltage trigger works from well-known BEAM builder Wilf Rigter.

Here is a schematic for the basic FLED SE circuit, taken from Beam-Online.

Parts List

Here’s the list of parts that Zach uses to build a basic single-motor Vibrobot. Solarbotics parts numbers are given, but you can also get many of these parts from your own techno-junk collection, from Radio Shack, or other electronics sources (see “Resources List” below).

Quant Part Solarbotics Parts # Notes
Pager Motor #RPM2 With weight still attached
3v Solar Cell #SC2433 Any 3v cells, such as the 24mm x 33mm ones SB sells
4700uF cap #CP4700uF N/A
2N3904 NPN transistors #TR3904 N/A
2N3906 PNP transistors #TR3906 N/A
Flashing LEDs #FLED N/A
2.2K-ohm resistors #R2.2k N/A
Heat Shrink Tubing N/A Radio Shack has an assortment in various sizes. You’ll want tubing all the way up to 2″ dia.
Medium-Size Paper Clip N/A N/A
Guitar String N/A N/A
Red and Black Hook-Up Wire N/A Used to attach solar cell to SE circuit

This bot has two pager motors. The first one (on top) has a fan attached to it. This doesn't have much purpose besides offering some kinetic visual interest.

Zach’s Building Tips

Zach offers the following bits of additional bot-builder wisdom for success in creating your own Vibrobots:

  • The key to a good Vibrobot is to keep it as lightweight as possible so the motor can really jiggle it around when it fires.
  • Play around with leg placement. Having only a couple of the legs touching the ground at the same time can create some interesting movement patterns.
  • Buy a pack of jumbo- and regular-sized paperclips. For the US$2 you spend, you’ll be able to build a whole fleet of robots. I almost exclusively use paperclips and guitar strings for my creations.
  • An assortment pack of heat shrink tubing goes a long way. Not only are your bots more interesting-looking, but you can use the tubing in key places to reinforce weak joints. I rarely have two strips of heat shrink on top of each other just for visual appeal.

This dual-motor vibrobot has the ends of paperclips soldered to two pager motors. Each motor is connected to a CdS cell so the more light each "eye" gets, the more the motor on that side fires. It's great to watch it react to a flashlight.

Resource List

Here are a few of the parts suppliers and websites that Zach (and I) recommend when planning out a BEAM project.

Solarbotics These guys are the go-to source for everything BEAM. I’ve been buying from them (and working with them) for many years and have always been impressed with their intense devotion to the BEAM hobby (and their customers).

Hobby Engineering Good source for motors, robot kits, parts, and other geekly goodies.

Goldmine Electronics I’ve never met a hardware geek who didn’t heart the Goldmine. If you’re not on their free catalog mailing list, get on it! It’s a treasure-trove of weird and wonderful parts and deep discounted gadgets.

Mouser Zach sez (and I concur): “Great for any extra parts you might need. You may be able to find parts a little cheaper elsewhere but I’ve found that their fast shipping and great packaging (every item comes in a clearly marked bag) makes it worth any savings you might find elsewhere.”

eBay Several good places in Hong Kong offer cheap LEDs via eBay. The BEAM community portal. The Library section drops all sorts of mad science on BEAM theory and practice.

Beam-Online Another venerable and useful site for all things related to BEAM.

Zach’s BEAM Bots on Flickr To see additional (and hi-res) versions of these images, and Zach’s other bots, check out his Flickr page. To learn more about his design and fine arts work, visit his website.

This basic vibrobot uses a polyacene battery instead of a cap (to deliver about .6F of power). The bot gets a decent power burst when it fires. It also has a guitar string "nose" to help keep it away from larger bots.


Other Robot Projects from Street Tech

[Dead Inventors]

Sergei Pavlovich Korolev: The Soviet Space Program’s Secret Mastermind

by Gareth Branwyn a cold, gray morning in October 1947, outside the Soviet city of Volgograd, a group of men watch in wonder as a huge rocket rumbles skyward from a hastily erected launch pad. Two years of intense effort to piece together a German V-2 rocket have finally paid off: The first Soviet ballistic missile has taken flight.

A stocky man in a dark leather coat is particularly enthusiastic. From this moment until his death, Sergei Pavlovich Korolev will be the moving force behind the Soviet space program. In only 10 years he and his team will stun the world with the launch of Sputnik, followed by a string of other historic firsts.

Yet Sergei Korolev will be forced to live a life in secret: Others will be given credit for some of his immense accomplishments. Even after his death in 1966, accounts of Korolev’s life will be clouded by hearsay, and official histories will obscure the true story of this remarkable man. in Ukraine in 1907, Sergei Pavlovich Korolev became fascinated with aircraft at a very early age, watching planes at a naval airstrip near his home. In 1928 a 21-year-old Korolev entered Bauman Technical University to study aeronautical engineering; in 1931 he co-founded GIRD (Jet Propulsion Study Group), an unofficial organization experimenting with liquid fuel rockets.

Korolev was arrested by the Soviet secret police in 1938 during Stalin’s purges and was accused of “subversion in a new field of technology.” He was initially sent to the dreaded Kolyma gold mines in Siberia. But Stalin couldn’t afford to let his rampant paranoia slow down his engines of progress, so Korolev was transferred to a special prison for scientists and engineers where he was allowed to resume his rocket research.

After World War II, the engineer was sent to Germany to study captured V-2 technology, and was put in charge of a design bureau responsible for ballistic missiles. But inspired by the writings of Russian space visionary Konstantin Tsiolkovsky, Sergei set his sights higher than the battlefield. When a colleague questioned the military readiness of his rocket design, Korolev angrily replied: “The purpose of this rocket is to get there [pointing spaceward]. This is not some military toy!” was the inexhaustible force behind a staggering number of space projects: the first intercontinental ballistic missile, first satellite, first man in space, first spacewalk, first spacecraft to impact the Moon, first craft to Venus, first Mars flyby, first spy satellite. James Harford, executive director-emeritus of the American Institute of Aeronautics and Astronautics, sums up this great engineer’s place in history: “Korolev dominated virtually the entire Soviet space program. His feats, and those of his design bureau, would have to be equated to those of dozens of U.S. space leaders, companies and NASA centers.”

Nov. 16, 1965, was to be the last launch date that Korolev would ever see. The Venera-3 probe was set on a course to Venus, to become the first craft to impact another planet. In January of 1966 Korolev checked himself into a hospital for a colon operation. Years of poor health brought on by harsh prison conditions and workaholism had taken their toll; Korolev died on the operating table. His Pravda obituary the next day was the first time Korolev was ever identified as the chief designer of Soviet space rocket systems. Abramov, who worked in Korolev’s design bureau, said of his former boss: “He was … an intellectual and a skilled craftsman. … While observing Korolev during our time together, I caught myself thinking he was from another planet … a character in a dream.”

The following originally appeared in Discovery Online’s “Dead Inventors” column, March 1997]

Twin-Engine Solarroller

Gopod bless Flickr! While searching on it recently to see if anyone else had built Mousey the Junkbot or a Symet or Solarroller inspired by my recent BEAM robotics articles in MAKE, I discovered Zach DeBord and his amazing BEAM creations. A Chicago-based designer and Web developer who’s done work for (among others) Comcast, Volvo and Yellow Tail (mmm…wine), Zach’s bots put the “A” (as in “Aesthetics”) back into BEAM, with gorgeous, meticulous designs that are as much objets d’art as autonomous robo-critters.

All of his robots are awesome-looking, but I was instantly attracted to this roller because it’s bigger than any solarroller I’ve ever seen and it uses two solar cells, four storage capacitors, and two gearmotors. Ingeniously, this roller can be steered (sorta). Zach writes: “It is currently configured to go forwards, but by angling either solar panel, it will turn more in one direction since one panel will be getting more light. With both panels angled in the same direction, it is pretty phototropic.”

The two large drive wheels on the roller where made from the discs in old SyQuest 270MB 3.5″ removable cartridges. Of these, Zach sez: “The SyQuest platters make great wheels except that they are fairly slick. I plan on getting some rubberizing paint and putting beads along the edges to give the wheels more traction.” The third wheel, an idler, “keeps the motors from dragging on the ground. It is actually a small plastic part also taken out of the SyQuest disc.”

For this design, Zach used two FLED-based voltage-triggered Solar Engines (Type 1). In my “Beginner’s Guide to BEAM” and the “Two BEAMBots” projects in MAKE Vol. 6, we also discussed and used voltage-triggered Type 1 SEs, but they used a 1381 voltage detector IC to control the circuit. FLED-based SEs use a Flashing LED (hence “FLED”) in place of the 1381. On the FLED SE page on the Circuits Library on, this is how BEAM guru Wilf Rigter describes the way in which such a circuit works:

“The solar cell charges the main capacitor until the voltage is high enough for the FLED to start flashing. When the FLED flashes, current flows through the FLED and the base of the PNP transistor and it turns on. Now current passes through the PNP into the base of the NPN transistor and it turns on. When the NPN turns on the collector which is connected to the motor and the 2.2K resistor goes low (to GND). This places a voltage across the 2.2K resistor which provides more base current for the PNP transistor which makes it turn on even more. That is called positive feedback or latching of the circuit because both the PNP and NPN transistors remain on until the main capacitor is discharged to less than 0.7V. When the capacitor voltage drops below 0.7V the PNP and NPN transistors both turn off because of the minimum voltage required to keep the base emitter turned on.”

Here is a schematic for the basic FLED SE circuit, taken from Beam-Online.

Zach on building BEAM Roller circuits: “I usually build engines in a batch for later use. In the image below, you can see that there are sockets on top of the engine circuits (made from IC socket pins). These are used to easily plug in the solar cells. The two leads (red and black) coming out of the back of the engines go to the motors. In this picture you can see the two types of engines that I make: one “classic” configuration with storage capacitors (the two engines on the left) and another config using Polyacene disk batteries in place of the caps (which deliver roughly .6 Farads of stored power). These are represented by the three engines on the right.”


Parts List

Here is a list of the parts that Zach used to build his bot. Solarbotics parts numbers are given, but you can also get many of these parts from your own techno-junk collection, from Radio Shack, or other electronics sources (see “Resources List” below).

Quantity Part Solarbotics Parts # Notes
SyQuest Disc Platters N/A Dumpster diving, anyone?
3v Solar Cells #SC2433 Any 3v cells, such as the 24mm x 33mm ones SB sells.
Gear Motor GM3 #GM3 These are 224:1 90-degree shaft motors
2200uF caps N/A N/A
4700uF caps #CP4700uF N/A
2N3904 NPN transistors #TR3904 N/A
2N3906 PNP transistors #TR3906 N/A
Flashing LEDs #FLED N/A
2.2K-ohm resistors #R2.2k N/A
IC Socket pins #SPin24 These are on a 24-pin DIP that you pull off to use.
1/2″ piece of 1/4″ tube N/A Used as a spacer between engines.
1.5″ screw N/A To fasten engines together (via hole on motor casings. You just need to find a screw that’ll fit snuggly.
Round plastic piece N/A To be used as back stabilizing wheel. Zach got his from the same SyQuest disc.
Heat Shrink Tubing N/A Radio Shack has an assortment in various sizes. You’ll want it all the way up to 2″ dia.
Heavy Duty “Jumbo” Paper Clip N/A N/A
Hook-up Wire N/A Use red and black to keep things colorful and polarity-coded.

Zach’s twin-engine roller next to a more
common single-engine variety.

Resource List

Here are a few of the parts suppliers and websites that Zach (and I) recommend when planning out a BEAM project.

These guys are the go-to source for everything BEAM. I’ve been buying from them (and working with them) for many years and have always been impressed with their intense devotion to the BEAM hobby (and their customers).

Hobby Engineering
Good source for motors, robot kits, parts, and other geekly goodies.

Goldmine Electronics
I’ve never met a hardware geek who didn’t heart the Goldmine. If you’re not on their free catalog mailing list, get on it! It’s a treasure-trove of weird and wonderful parts and deep discounted gadgets.

Zach sez (and I concur): “Great for any extra parts you might need. You may be able to find parts a little cheaper elsewhere but I’ve found that their fast shipping and great packaging (every item comes in a clearly marked bag) makes it worth any savings you might find elsewhere.”

Several good places in Hong Kong offer cheap LEDs via eBay.
The BEAM community portal. The Library section drops all sorts of mad science on BEAM theory and practice.

Another venerable and useful site for all things related to BEAM.

Zach’s BEAM Bots on Flickr
To see additional (and hi-res) versions of these images, and Zach’s other bots, check out his Flickr page. To learn more about his design and fine arts work, visit his website.

Blow Your Socks Off! (The Bell Rocket Belt)

By Gareth Branwyn

April 20th, 1961. Next to the taxiway of the Niagara Falls Airport, engineers from Bell Aerosystems have set up equipment for an altogether new kind of flight. A young engineer, Harold Graham, straps a bulky contraption called a rocket belt onto his back. As Graham engages the belt’s throttle an immense blast of steam erupts from the rocket nozzles. Out on Niagara Falls Boulevard a driver does a double take and wheels into a ditch as the world’s first rocketman pops out of an immense steam cloud and shoots into the sky.

Originally conceived in 1953 by a wildly inventive Bell engineer named Wendell F. Moore, the rocket belt was part of an Army contract to create a “small rocket lifting device” that could improve soldier mobility and maneuverability. While the April 20th test flight and hundreds that followed were promising — especially as jet engines replaced rockets — other defense and aerospace priorities of the 1960s grounded further R&D.

Harold Graham demonstrates an
experimental rocket lift.

A funky thing built mainly from scrap and off-the-shelf parts, the rocket belt consisted of fuel tanks, handlebars, a control throttle and a pair of rocket nozzles. Hydrogen peroxide (H2O2) fuel was fed over fine silver mesh, which acted as a catalyst to produce 1,400-degree steam. The steam was then forced through nozzles to unleash 330 pounds of thrust and 135 decibels of brain-rattling sound.

Inventor Wendell Moore observes a test run.

The belt offered a surprising degree of maneuverability — its pilot could fly, hover, spin, negotiate tight turns and make pinpoint landings. But it was not without problems. Bill Suitor, one of the original belt pilots, recalls that during an early tether flight the control stick snapped off in his hand. He hung on for dear life as spotters yanked control ropes to keep him from crashing.

The biggest stumbling block was limited fuel capacity. The belt’s recycled Air Force oxygen tanks could only hold enough H2O2 for a fleeting, 23-second flight. During one show, rocketman Suitor accelerated too quickly and discovered to his horror that he couldn’t slow down. “I was at 114 feet when I looked at the fuel gauge and saw I had only a few seconds to land. I was about 3 feet off the ground when the fuel ran out.”

Anatomy of a hydrogen peroxide rocket belt

Despite James Bond’s pronouncement in the movie Thunderball that “no well-dressed man should be without one,” the rocket belt never caught on. Four copies of the original Bell belt were made. Three of those are now in museums; one ended up on the scrap heap.

Nevertheless Hollywood was intrigued. A version inspired by the original Bell model and crafted in the late ’60s by inventor Nelson Tyler — who Bill Suitor says is a dead ringer for the mad scientist in Back to the Future — saw celluloid action with Suitor, who did 007’s stunt rocketeering and appeared in dozens of commercials, TV shows, movies and special events such as the 1984 Olympics. Noted Hollywood stuntman Kinney Gibson has also used the Tyler belt.

Despite James Bond, the rocket belt never took off.

Brad Barker of American Flying Belt recently unveiled a further modified design. He’s published a technical manual and video about his RB-2000, and has offered to manufacture a rocket belt for anyone who cares to bankroll one. Though Barker’s belt burns five seconds longer, Suitor and others say its advances are minor.

Still rocket belt veterans know that there’s plenty of room for improvement. Rumors abound of inventors developing a new generation of jet-powered belts. “You can get up to 30-minute flights with a jet engine,” says Suitor, “which could offer all sorts of uses for search-and-rescue, fire inspection, law enforcement, flying camera operators and so forth.” Bell Aerospace actually licensed a jet-powered version of the belt to Williams International in 1970, but development of Bell/Williams “small lift devices” was halted after Williams’ small jet engine — the only engine of its kind — was earmarked for exclusive use in the cruise missile.

Bill Suitor lands during the 1984 Olympics.

“It was technology 50 years ahead of its time,” sighs Suitor, his voice carrying no small amount of nostalgia — and a little bit of hope for the future of this tech.

Rocket Belt Movies

[This article originally appeared on Discovery Online in 1997, as part of their Alt.Tech series]

Pictures: Arnold Sachs/Archive Photos | UPI/Corbis-Bettmann | Dean Conger/National Geographic Society | Courtesy of William P. Suitor | Springer/Corbis-Bettmann | Jacques Cochin/Vandystadt/Allsport |
Video: Archive Films | Courtesy of Pabst Brewing Co./Collection of William P.Suitor/Rocketman Enterprises |
Copyright © 1997 Discovery Communications, Inc.

The SCO Monkey Trial (A Street Tech Intro)

By Bruce Dykes

SCO used to be a Linux company called Caldera. They bought AT&T Unix from Novell, who bought it in the early 90’s, but did nothing with it, choosing instead to battle Microsoft in the desktop app arena with WordPerfect and Quattro Pro.

Caldera’s goal was to build a common environment between AT&T Unix, and Linux. SCO’s brand of AT&T Unix had a respectable installed base, and an impressive reseller channel. Caldera found it a more difficult strategy than first thought, the original board wound up moving on, and Caldera found itself under the direction of The Canopy Group and Darl McBride.

The original SCO, Santa Cruz Operation had renamed themselves Tarantella, and gotten out of the OS business in favor of network management software. One of Darl’s first moves at Caldera was to buy the SCO name from Tarantella and rename Caldera to The SCO Group (SCOX).

Brought on board to increase revenue, he started casting about for untapped potential, and he discovered the original AT&T Unix licensing contracts with IBM.

Older geeks will remember the DR DOS vs. Microsoft lawsuit, where, in the early days of Windows 3.1, Windows was programmed to produce error messages when it was loaded on top of DR DOS. Darl McBride headed the company that bought DR DOS, and the lawsuit against Microsoft, and won a decent settlement, so naturally, he thought litigation was the best way to put SCO/Caldera in the black.

The first thoughts when they announced the lawsuit vs. IBM was that it was buyout bait – they were suing for [pinky] one billion dollars! A sum large enough to get themselves noticed, and hopefully bought out to go away.

They selected David Boies to represent them. You may know him from such lawsuits as RIAA vs. Napster, or Al Gore vs. the Florida Election Commission. From those cases, one thinks SCO might have been better represented by Lionel Hutz, but he did win when he was representing the DoJ vs. Microsoft (it was on appeal that M$ was able to get their punishment neutered), and he also represented the government in their antitrust case against IBM, so not a bad selection in and of itself, but hardly promising, either.

IBM is the single largest holder of patents in the country. Entire families of IP lawyers have been raised for the sole purpose of managing IBM’s patent portfolio. Taking them on in an IP battle is the legal equivalent of launching an overland invasion of Russia in September.

After poking the dragon, and being shocked to learn that not only didn’t the dragon want to pay them for their valuable service in waking it up, but was in fact rather more interested in setting them aflame, the common belief is that they changed their strategy to a pump-n-dump run on the stock.

SCO is accusing IBM of violating contractual clauses in their Unix license that prohibit them from taking any software developed for Unix System V, and releasing it into Linux. Please note that they’re not accusing IBM of any copyright violations, or patent infringements, just breach of contract, no matter what else they may be saying to the press.

There’s a few problems with this:

1.a. The contracts don’t prohibit taking software developed for SysV and releasing it as a separate product – they prohibit taking software developed from the SysV code and releasing it as a separate product.

1.b. AT&T sent out side letters to all AT&T licensees to clarify that point that anything developed independently was the product of the developers, and not considered a derivative of the SysV code.

1.c. Novell, the company that sold Unix to SCO, says not only didn’t they sell the totality of all Unix rights to SCO, they still have the right to veto any amendments that SCO wants to make to the licensing agreements, and they’re vetoing any attempts by SCO to revoke IBM’s Unix license.

1.d. While SCO hasn’t exactly been forthcoming with the code in question (remember, they’re only charging IBM with breach of contract, not IP any violations), all their statements to the press have hinted at three different code groups under the SMP (Symmetric MultiProcessing) section of the Linux kernel: JFS (Journaled File System), NUMA (Non Uniform Memory Access), and RCU (Read Copy Update). The problem with that is, all that code was developed independently of any SysV code. JFS was created at IBM, and RCU and NUMA were developed by Sequent, also an AT&T licensee, and also independently of any SysV code.

2. Damages.
2.a. SCO brought the lawsuit back in April. But for all their talk of IP infringement, they refuse to identify the code and allow it to be cleaned from the kernel. Darl has gone on record to say he doesn’t want that to happen.

2.b. What’s more, they’ve been discovery ever since, and so far, SCO has refused to provide any examples to IBM of this allegedly infringing code. Since April. There’ll be oral arguments in court today where IBM says they’ve given SCO what they can, but without SCO being more specific, there’s only so much they can do, while SCO’s counter is that IBM and only IBM knows what code they copied into Linux, therefore it’s down to them to provide the code that they copied, and SCO has no way of knowing what that code may be.

You may notice something about that last item. It’s in direct opposition to multitudes of public statements made by SCO principals over the past several months. There’s one piece of legal advice that any lawyer, anywhere is going to give you for free: shut yer yap! With every statement, SCO’s been putting its feet in its mouth, then pulling the trigger to put a few rounds into them.

And that doesn’t even begin to start covering the IBM countersuit, and the suit by Red Hat charging tortious interference.

The single best source of info on the trial is:

Gar’s Tips on Sucks-Less Writing

[Here’s something I’ve been working on, in dribs and drabs (mostly drabs), for the past four years. The idea was to share a few tricks of the writer’s trade with Street Tech writers, many of whom were then new to the biz. I violate some of my own “rules” here. It’s a bit…ah…windy and even more than a bit redundant, but I decided that, in this context, it was OK. For instance: “Garage Band Writing Style,” “Shitty First Drafts,” “For God’s Sake, Have Fun!,” and “Writers Write” are all saying basically the same concept, only expressed in slightly different ways. One may speak to you where another doesn’t. Anyway, consider it a work in progress, one that I didn’t feel like keeping to myself anymore.