Another fun are litte motor driven units fueled by sunlight: Symets

and it's easily put together: a motor from a old cd-rom drive, some capacitors from an old mainboard and a solar engine (link to

the solar panel charges the capacitors up to a level and then the stored energy is released to the motor making the symet to move around.

symet 2
symet 2 this was the first try, but the capacitors are way too far above the ground, so this one got a wire coil.

the solar cell is a nice one from schott solar, making the symet to move without direct sunlight, but then it may be as slow as one move a minute ;-)

this is the second try and this symet is more compact with a cheaper solar cell amd a simple solar engine. as you see just the two npn transistor version with a resistor and a zener-diode. so this one needs sunlight to hop around. symet 1
symet 1 and here with the solar cell on top. as spacer to the solar panel two old button cells are just glued in between.

Some links about symets:

• many sources at Google images
• to the Junkbots Sample Chapter ( an excellent source
• solar engine at beam wiki (

And always don't forget: Have fun!

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Wed Jul 8 17:43:43 CEST 2009