I had a lot of fun working on this. I had to fight with the Miller engine a bit but was able to get a basic proto going, but more importantly, I think this is a project that I will gravitate toward in the future. I love that you can slap together a simple circuit like this and come out with a cool little robot. This project in particular also got my attention because it’s really easy to understand once you’ve put it together a couple of times and now I understand a bit more hardware than I use to and that makes me really happy (because I’ve lately been feeling like “I’ll never be MacGuyver,” but now I’m one step closer….). Pictures, videos, explanation:
This is the underbelly of the photovoltaic cell I used. The leads are thin, about 1.5″ long and are made of a specially engineered foil-like substance which, upon contact with human skin, destroys itself in a mysteriously magical fashion rendering the unit useless. To avoid this feature, I decided to just hot-glue the hell out of them so they are made idiot-proof (which is perfect for me).
I built the circuit and experimented with a few configurations of capacitors and found that I was digging the 2x4700microFerrad caps(at 6.3V) on the hot line with a 1microFerrad (at 50V) between the positive and negative pin of the voltage trigger.
I then transfered it to a new board and delicately soldered the new circuit and hot-glued the connections to keep them discreet.
Then I made a little spacer out of the extra board I had in order to straddle the glue job on the pv cell.
After the cell and foot were attached, I found that the torque in the tiny tiny motor I was using wasn’t enough to get it to turn itself around without assistance. It can handle the weight of the cardboard but not of the circuit and cell altogether.
I think that I could improve on this design in two places in particular. The first place is the extra capacitor between the positive and negative pins of the voltage trigger, which I believe makes the base of the 3906 transistor stay high longer so the voltage getting dumped out of the 4700microFerrad caps release slower, smoothing its capacity output as well. This could be cut out or replaced with a smaller cap which would squeeze more power out in a shorter amount of time. The second place is the materials. I used a little RadioSnacks printed board that I broke in half and hot glued together for the circuit architecture. The caps and the solar cells are not places that I have weight to spare (unless I de-idiot-proof the solar cell leads) so I could soften the circuit by removing the board and spacer which might give me a few hundred pounds worth of mobility. I think the silver bullet is really a bigger motor. With a bigger motor comes other bigger parts but I think I can find a reasonable weight balance pretty easily. Fun stuff, this and I will surely dive further in when summer comes around!