For green tinkerers and DIYers, nothing could be sweeter than building something from repurposed materials, except maybe when that something is a teaching tool for kids, especially when it's about renewable energy.
This little hydropower project is a nice example of what can be done with some scavenged parts, a little time, and some good old homegrown ingenuity. Instructables member masynmachien said that after staying at a place which generated its own electricity with a water wheel, he was inspired to build his own version in a workshop for kids. The resulting hydropower generator is tiny and powers just a single LED, but is also a potent example of what can be done with discarded tech parts and some imagination.
The only new material used in this project was some hot glue, and the rest of the materials were reused, including a small stepper motor from a printer, 2 discarded CD-ROMs, a foam tray, a piece of PVC pipe, an LED bulb, and some zip ties.
"Stepper motors make very easy generators, as they produce relatively high voltages (I’m talking 5V range) at low rpm. Small DC motors (toy motors) need high rpm and still produce only a low voltage (1V range). Stepper motors do not need gears and/or electronics to power a LED (compare it to my junior wind turbine). I was worried about blowing up the LED at first, but that did not happen. The current generated being pulsating very probably contributes to that." - masynmachien
Check out the full instructions at Instructables: Hydropower from Reuse