The circuit is really not too difficult. The important thing is that you will need a spool of magnet wire with a LOT of turns. There was no scientific method to the number of wire turns needed. I just bought a spool of magnet wire from Amazon, hooked it up to an oscilloscope, and dropped a rather large magnet through it. I saw 3-5V spikes and decided it was enough to light a white LED.
What you’ll need:
- Spool of magnet wire
- Rather large (3/4″) neodymium (rare Earth) magnet
- Perf board (or solder-able breadboard)
- 4x diodes
- A large capacitor (I used 220uF. Anything around there will work.)
- 220Ω resistor
- White LED
- Wire (I recommend solid-core wire for this)
- Soldering equipment
The spool I bought from Amazon did not have both ends visible. I needed to unwind the spool, pull out the end taped to the core of the spool, and re-wind it. I did this on a lathe, but anything that spins would work (e.g. a drill). You could also re-wind it by hand, but that might take some time.
Here is the circuit:
Solder up the components on the perf board as per the schematic. After that, drop the magnet through the spool!