Thank you, Bigboat for the lead on transformers.

Last week, I made a trip to a local surplus store and picked up an assortment of ferrite toroid cores. The first one I tested was 17mm O.D. X 10mm I.D. X 6.7mm high. I used 32AWG for the secondary (400 turns) and feedback, and 25AWG for the primary. It was just for a test and the limit on turns was because the shuttle I made for winding was too big for the hole as the windings increased. The circuit was modified to use an NPN transistor and I used a voltage doubler for the output. So far, it seems to work as good or better than an import ignition from China. By "better" I mean the spark intensity and stability seems better at the highest test RPM (about 18,000 rpm). Maximum peak current during charge is about 900 mA, as estimated with an oscilloscope and small rsistor.

I plan to do more characterization and comparison of it today with the Chinese ignition. It was just plain fun to see it work so well and be so simple.

As I read more on ferrite cores, it seems the choices are almost limitless, and the characterizations and color coding schemes are completely unstandardized. I would like to be able to describe what I do, so it can be reproduced. Not everyone can visit the same surplus store in Cleveland that I went to. So, the core I chose to use in my initial test was the only one with an identifier number on it. That number is: 2D10-55115-A2-2. I have searched Google and cannot find any technical data on it. PartMiner lists that number, but has no other information. It is grey and has a smooth epoxy-like coating. Does anyone have any idea what its characteristics and/or manufacturer is?

John