Re: How do Atom Computer Ignition modules work?

[legendre]

I have this circuit set up on a breadboard, though I’m using a 6V Bosch coil (from a Puch moped) and a 6A 6.3V transformer for power. The coil’s primary winding is wired in series with the 6.3V transformer secondary – I believe this should be a reasonable stand-in for the flywheel alternator on an actual motor, though I could be wrong..

But if we assume a simple, single-coil, single-magnet alternator, 60Hz AC should be the equivalent of 3600 RPM – which is about the top speed for most small outboards, I’d guess?

In any case, according to the o-scope, the module +is+ being triggered, but I’m not seeing any spark. Unfortunately, I don’t have a HV probe right now, so I can’t easily measure activity on the coil’s HV secondary. One thing, the 1071 is getting pretty warm, so I’m thinking it’s not fully saturating – I don’t have the BC337 driver transistor that debe used, and my replacement may lack sufficient gain.

Thoughts on a suitable drop-in for the BC337? ETA: Apparently, the venerable 2N3904 might be OK.. and I have them.

Have checked the coil, and it will make snappy, bright 1/4" sparks when tickled with an 8V DC supply. Will have to putz with it some more, later this eve.