Re: How do Atom Computer Ignition modules work?

[legendre]

quote Mumbles:

The module doesn’t know how to advance the timing. It wasn’t designed to. The original Red Atom for outboards work the same but spark advance is achieved by rotating the mag plate.

Ideally, the Red module shouldn’t create any dynamic advance or retard – following only the advance curve of the movable stator plate. But per my understanding of the laws of induction, a circuit of this type should +tend+ to produce an advance behavior with increasing RPM, unless the circuit is additionally designed to squelch it.

quote :

Briggs motors have no mechanical advance system.

Far as I know, no they don’t – at least not the typical lawnmower / snowblower motor we’d be most familiar with. Doesn’t mean it might not be advantageous, though! Sure, the motors run ‘right’ with fixed timing, but if cost / complexity were not an issue, I’d expect to see dynamic advance on these motors.

quote debe:

(…) Next point is for reliability don’t use paper type electrolytics as in your picture, they will dry out & fail in a hot environment. Use Polyester MKT types as in the original pictures. (…)

This is a very Good Point. I’ve been using aluminum electrolytics in my modules, simply because I had nothing else on-hand in that low value. I know it’s not helping the performance of my modules, and plan to get rid of them ASAP.

The AEs may even be responsible for the retard-at-speed behavior I’ve clearly observed.

quote mercuryman:

You will need to mount the power transistor on a heat sink and insulate the heat sink from transistor. Looks good to me.

FWIW, the (Darlington) transistors in my modules have never gotten even warm.. this with the either of the successful devices.

Were the original modules heatsinked? I don’t think so.. or at least, not robustly.

Looks like they have a little brass ferrule that admits a mounting screw though the hole in the TO-220 case. But none of this provides the intimate contact you’d expect in a heatsinked part.

The plastic case on the Atom module is a poor thermal conductor.