I built the beginning of a BEAM robot: it moves in the light. Using a blinking LED as a diode that allows it to pulse rhythmically. I’m using a small capacitor (2200 uF), but using a clamp light, the solar panel charges to about 4.5 V.
I’d like to use an oscilloscope to see more of what’s going on.
I used this circuit from this site
Maybe my BEAM can even have this FM receiver circuit, for, say, a microphone, so it will respond to sound?