This is a small magbot hopper made from spare parts I had laying around. I've been meaning to make one of these ever since I saw Tilden's bot. Originally I had planned to make it phototropic using two coils, but this would propably have been to heavy. Naturaly, weight is very important for a bot of this kind, this one only weighs 10 grams including the magnet. 640 uF of power storage might not seem like much, but it is sufficient to make the bot "jump" about half a millimeter everytime the solarengine fires, and it fires often. The aluminium on the solarcell is there because the cell was pretty badly damaged, and this way it looks a little better. The bot rests on the magnet, and when the solarengine dumps the power thru the coil it pushes against the magnet and the bot makes a small jump (making a really irritating click-click-click sound).
This is a funny looking little bot. Like a small box that moves around mysteriously... In the left picture you can see the magnet in the center and the coil behind it. The magnet is held in place by the small spring on the right. The LED is wired in parallell with the cap "backwards", so it lights up from the pulse from the coil, but you can't see this when the light-level is high enough for the bot to operate.
Power storage: 640 uF, 2 * 220 uF + 2 * 100 uF electrolytic
Motors: Solarbotics "Major Henry" coil and neodynium magnet
Cells: 24*22 Panasonic sunceram.
Solarengine: Standard FLED solarengine
Contruction time: 3 h