I built a high voltage board which worked OK - though my voltmeter recorded between 500V-600V from 6V input. I had a few odd behaviours with the SCR triggering the spark: the spark would trigger, but only start to recharge when I earthed the trigger.

Also, I only triggered a spark when I used a 1.2V power source as the trigger, I tried connecting directly to a Hall sensor but it didn't work. I don't understand the requirements of the Hall trigger circuit to trigger the CDI system. Any clues?

My high voltage coil is wound on an E-core. I would rather spend $200 on a professional CDI than wind another toroid coil! The E-core coil only took about 20 minutes to wind.

Thanks for the informative page, Jon.

Cheers,

Ben