And now, a completely unnecessary distraction.
While digging through the parts pile for stuff to help build Sawppy’s wiring, I came across an electronics kit that has been sitting, waiting to be built, for over a decade. Every time I came across this kit I decided “I’ll build it later.” And even though I’m in the middle of building rover wiring, I looked at this kit today and thought: “I kept saying I’ll build this someday… that day is today.”
I’m not sure how old the kit is, but I’m quite confident it’s been over a decade. The only date visible is the last revision date on the manual – August 25, 2003. The manual said it is version 4.2, the Solarbotics catalog is now up to version 5.0. I thought its age wouldn’t be a problem, it’s not like electronic components decay, right?
It’s a simple little kit of through-hole solder components. The first step – like all kits new and old – is to lay out all parts and check against the parts manifest in the instruction. Once all parts are accounted for, assembly can begin. Given the growth in my electronics skills over the past years, this “Skill Level 3” kit is now a breeze to assemble.
It took only about half an hour to reach the point where all power components are connected. I am instructed to take the partially built robot someplace bright to give the solar powered system a test. I placed it under sunlight and… nothing.
First I ran through troubleshooting steps outlined in the manual, and none of them helped. So it was again time to deploy skills I didn’t have years ago, this time for electronics debugging. Out came the multi meter and start probing the circuit.
Diagnosis: the electrolytic capacitor is dead. Remember when I said electronic components don’t decay with age? Well, that was wrong because electrolytic capacitors do. Back into the parts pile I go and I was able to find another 4700 uF capacitor. Problem: it is physically a far larger device. In this picture, the dead capacitor from the kit is on the right, dwarfed by the new functional capacitor on the left.
Since the functional capacitor is much larger physically, it couldn’t fit in the same space under my photopopper. The big capacitor would have to go above. The dead capacitor also served as the third leg of the photopopper, so that job had to be reassigned to a little piece of wire. Now the robot sit on the wire instead of a capacitor along with its two wheels.
And now… it moves! The little solar panel charges up the capacitor, and ever few seconds that power is dumped into one of the electric motors, scooting the photopopper a tiny bit forward. A process that will repeat for as long as there’s light shining on the solar panel. I’m sure that it would move farther or maybe faster if the original sized capacitor was in place. This poor photopopper has to carry a big heavy barrel of a capacitor on its back.
Technically the kit has not been completely assembled. There are also two touch sensors that help the photopopper detect walls and steer away from them. But given that it is moving, and that I wanted to get back to assembling wiring for Sawppy the Rover, I’m content enough to leave the photopopper as is. I’ll pull it out every once in a while, so I could put it under sunlight and let it scoot around.