Dumpster Divin': The Student's Jaycar

With the availability of processors like Arduinos, It's easy to forget that complex behaviour can be made out of analog circuits scavenged from garbage.

My number one childhood reference book.

The book that first got me into electronics was Junkbots, Bugbots and Bots on Wheels by Dave Hrynkiw and Mark W. Tilden. It told great tales of interesting robots - solar-powered racecars, mini-sumo robots, light-chasing robots, a magnetically accelerated swing and a walking robot all made entirely (or at least, mostly) out of electrical junk.

I was amazed by what complex behaviour could be squeezed out of relatively few analog components, all based off energy harvesters and simple oscillators. It seems that analog electronics are rapidly dying out, and now seem to only serve the purpose of regulating the power supply to digital microcontrollers. BEAM robotics has "Keep It Simple, Stupid" as one of its core principles - if your robot is meant to follow a line, you don't need an Arduino running 8 million calculations every second to compare the infrared reflectance to a predetermined threshold when an op-amp will do just fine. In the modern scheme of  "just microcontrol it," one is always firmly under the yoke of compatibility - logic levels, clock speeds, encoding formats and other irritating details that are irrelevant to the problem at hand 99% of the time. The advantage of pure-analog circuits is that most of the parts can be found, not bought.

Clockwise from top right: high-quality ±5V, ±12V power supply, 1000W microwave transformer, plastic box for future projects, well-loved flyback transformer

I've sourced many rare and unusual components from garbage found lying by the side of the road - electrolytic capacitors from an old dial-up modem, an IR receiver module, microswitches and geared motors from a VCR, inductors from an ancient motherboard and an enormous transformer from a microwave. Taking apart old appliances for parts, besides having its own perverse destructive joy, means that in a pinch you can grab obscure parts near your house rather than ordering them from eBay and waiting 3 months for them to arrive. The best part? Everything's free, and you're helping to reduce the quantity of harmful e-waste in landfill.

 

Clockwise from top right: high-quality ±5V, ±12V power supply, 1000W microwave transformer, plastic box for future projects, well-loved flyback transformer

Of course, these parts aren't really free - they cost you time and irritation in liberating them from their leaden prisons (Solder sucking, pulling and a well-placed strike from a hammer are my methods of choice) but I can assure you the effort is more than repaid by the fun it is to pry open commercial products to see how they work, then resurrecting the dead machines as simple analog toys that have a surprising amount of personality. I can only encourage you to try your hand at it yourself.

 

BEAM robotics are discussed on this very old (and very broken) website, but the content is no less relevant today. 

Written by Alaric Sanders (professional.events@mueec.com)

Melbourne University Electrical Engineering Club

2017

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