Last week I was scavenging through my son's toys. I found one with a geared dc motor.
Looked very promising. I designed a circuit to make a hand crank torch. So here it goes.
Step 1: Schematic
The circuit that I got used a capacitor to store the charge that was generated from cranking motor. But I stripped it to just glowing 2 LEDs. I did not find any capacitors or diodes in the circuits.
Step 2: The Housing
Measured the motor+gearbox dimensions and made a box with card paper to hold everything. The largest section of the gearbox was just under 2 inches. So I made the box as 2x2x2 inch.
Step 3: Finally
Now glued the LEDs and put everything together with glue. Now the box is a totally enclosed thing.
For the crank! I planned to make a handle but a flat piece of wood looked more promising. I will be drilling a hole (the size of a thumb so it can be cranked easily. The handle is attached to the axle with a little mseal putty and air dried.
So now If you crank it clock wise one LED glows and going other ways the other LED glows. I am planning to add the capacitor and the switch the next time I make a trip to the electronic store.
Also I am planning to paint it in funky colors so that my kid can play with it!