Coil Prototypes

Found some old bobbins and coil formers to create the windings. The wire is #32 AWG. This is OK for the prototype, but for the final piece ill use much thinner wire and a better coil former (something that has a bit of a lower profile). Im using the larger wire for now as anything smaller than #32 is a pain to wrap, it just breaks to easily.

I wrapped a couple of test coils on the small coil formers. These have 50, 100, and 150 turns respectively. The voltage spikes caused by the coil passing the magnet should be proportional to the number of turns (Faradays Law -- special case with multiple coils of wire, Electromotive Force is equal to the number of turns times the time derivative of the magnetic flux. so... more turns is proportionally more EMF, if we keep the speed and distance between the coils and magnets the same. Electromagnetic Induction. ) These three coils should let me show this relation. Then i'll extrapolate the number of turns i need for the voltage spike amplitude i want. I think it will be quite a few more than 150 turns in the end.

 I built two prototypes, both with full bridge rectifiers on the outputs, and just a resistor (100Ohm) to load the circuit. The left prototype uses the 150 turn coil, while the right most one uses a new 300 turn coil made on an old PQ bobbin i found.  Im a bit worried about the voltage drops on the diodes, but ill test it tomorrow to see if this will work. If not, ill just use a single diode half wave rectifier. (The full bridge rectifier catches both positive and negative voltage spikes, but causes two diode forward voltage drops. As i'm dealing with low voltages, this may not be ok. A better option at this level, may be to just use a single diode. This will loose half the energy from the coils as only positive spikes can be harvested, but may be better overall. We'll see. Full Wave Rectification. ) The energy harvesting guys will be in on monday as well, so ill ask them if they have leftover rectifier diodes for low voltage applications. They should have just what i need.