New Coils - Finishing the Prototype

 The new coils for my prototype boards are finally done! Using two old PQ cores, i wrapped as many turns as i could of AWG34 wire. This should be about 4-500 turns based on some old tests, which should give me a reasonable voltage on the output. Using some old plexiglass that we have laying around, i'm going to make a coil holder to make the tests easier. The coils are in series, and i'm planning on placing them so that they are individually excited by the magnets.  Some old tests showed that  if they are excited at the same time, its hard to make sure they don't fight each other. So i'm hoping to avoid the issue altogether. heres a picture of the coil holder as i'm planning on cutting it out...

...and here is the final product... 

 In the end, ill use a laser cutter to get the right shape to mount this to my bike and make things a bit cleaner, but for now this is OK. The wire to the battery holders runs through this holder twice, mostly just to remove any strain on the connections when i'm moving this thing around. After adding some test-points which i initial forgot and fixing my diode rectifier which i messed up at first,  i was able to get some test results with the setup below.

The raw coil voltage is measured using a single ended passive probe, while the rectifier output is measured with an active differential probe. This is needed as the two sides of the rectifier have different ground references. Using a single ended probe on bot sides of the rectifier effectively shorts the grounds together through the scope. At high power levels, this doesn't make the scope happy, while at low power levels like in this circuit, it can simply mess-up the measured signals. Below, the coil voltage is seen in yellow, while the rectifier output is seen in purple.

Note that although the rectifier output says it has units of amps, it really is volts. (The diff probe i'm using doesn't like the scope i have, so the gains are messed up. Telling the scope your measuring current lets you fix this, just with the wrong units.) These waveforms are taken at about 6 or 7mph, and already we are getting 1-2V outputs! This is great, and really gives me more flexibility in the next revision. (The rectifier output is clamped at a bit above 1V, as its diode connected to the batteries. Voltages above this charge the batteries.) Additionally, you can see from the yellow coil voltage waveform that i placed the coils just barely to close together. It should be fine for now, but ill fix it eventually. you can also see that the first coil has a few more turns on it (higher spikes) than the second. This is also not an issue, and one i don't care about anyway as both voltages are high enough.

Next up, i need to make sure that the battery charging currents are reasonable, and then double check that i'm generating enough power with these coils to make this system self sustaining.

Complete First Revision

I finally got around to populating the boards. Everything seems to work well. The LED's are attached with a 12" wire, while the coil board is attached with a 6" wire. After a bit of trouble getting the correct blink frequency, it looks like this is a working bike light! I still need to do all the power measurements and such to make sure everything will work in the long run, but for now its nice to have a working board together.

I took a short video of the lights working, showing the different light modes. I balanced my phone on my coffee cup to get the video, hence the poor quality. In any case it does show things working.