My 2 year old daughter has recently become interested in a couple of solar powered robots that I built a few years ago so I thought I would share them here. Both bots were built from instructions in Make Magazine vol. 06. The first one that I made was a ‘Trimet’. The Trimet uses a 1381-based solarengine with three 4700uF capacitors in parallel to power itself.
Trimet
The second bot that I built was a ‘Solar Roller’. It uses the same 1381-based solarengine as the Trimet but this time with a single 0.33 Farad gold capacitor. The body and wheels were salvaged from a VCR and a cassette walkman.
Solar Roller
The 1381-based solarengine works like this: The solar cell charges the capacitor. As the capacitor gains more charge, the voltage across it increases. Eventually the voltage reaches the critical point for the 1381 and it supplies current to the base of the 3904 NPN transistor. This turns the 3904 on so that current is drawn through the motor and from the base of the 3906 PNP transistor. This current turns the motor and the 3906 on, effectively removing the 1381 from the circuit. The motor continues to run as the capacitor finishes discharging.
Solarengine schematic from www.solarbotics.net
To see some great solar bots go here.
