How do Atom Computer Ignition modules work?

[legendre]

@johnnyrude

Per the scope shots on the preceding pages, and my experiences trying to work with a breadboarded module, it seems they do have somewhat stringent requirements in terms of the powering / triggering waveform.

Sines will trigger my test module, but the coil won’t spark and the power transistor heats up, though not badly at the levels I was running. I haven’t done any work with it since that first go, so I don’t have much else to report.

I suspect that a proper benchtop test for these modules would require some custom instrumentation – in particular, a power amplifier driven by an appropriate (programmable?) signal waveform that approximates the critical characteristics of the magneto primary waveform. A sine alone will not cut it, but a tailored rectangular pulse train +may+ suffice. More testing is needed, and I don’t know if I have the equipment on hand to proceed much further.

One crazy idea.. capture the voltage waveform from an actual magneto, and use that to drive an audio power amp, which in turn drives a coil / module system. No reason it should not work, but it would require some screwing around to find out!

[phil-b]

I made the oscilloscope traces posted above with an OMC 3hp block bolted to a board, driving the flywheel nut with a hand drill.

You could capture the waveforms using the audio in ("sound card") port on a computer (suitably scaled and protected), and then play them back thru the audio output, using an amplifier to drive the coil / module.

Here’s an article from a reputable "maker" ‘zine:
http://makezine.com/projects/sound-card-oscilloscope/

[legendre]

quote Phil B:

You could capture the waveforms using the audio in (“sound card”) port on a computer (suitably scaled and protected), and then play them back thru the audio output, using an amplifier to drive the coil / module.

That’s pretty much what I had in mind.. though I hadn’t considered trying to use a PC soundcard to do the capture.

I was thinking that a DSO would do the capture, which could then be exported and processed. But I can’t think of any obvious, overriding reason that a simple PC sound card (again – carefully padded-down / scaled / protected as you mention) couldn’t do the job.

[debe]

legendre, just sent you an email with some more CRO pics using a square wave. The cro pics were taken from a cheep LCD CRO KIT from ( http://www.banggood.com/Diy-Digital-Oci … 69762.html) they sell for $23 US. Ive built 2 of them & find they are quite reasonable for the price. If you set them in NORM mode instead of AUTO they then will store the wave form when the signal is removed. It wont update un till a nother signal triggers it. All the CRO wave forms I sent you were done on this kit. Also good for checking CDI trigger coils.

[mercuryman]

I built a circuit and its not working. My test bed is a single Champion with Bendix coil ( which sparks fine with points) I used a electric drill and reversed the conection. The photo of BC 337 to 2SD1071 isn’t clear. I put the flat side of the BC 337 down.

[ken-w]

The flat side of the BC337 is up if you are following debe’s construction picture on the first page of this post.

[legendre]

quote mercuryman:

I built a circuit and its not working. My test bed is a single Champion with Bendix coil ( which sparks fine with points) I used a electric drill and reversed the conection. The photo of BC 337 to 2SD1071 isn’t clear. I put the flat side of the BC 337 down.

Ultimately, it’s best to follow the schematic rather than trying to produce a working circuit by duplicating the physical layout. Then there’s no question about what goes where.

[ken-w]

Whats the deal !!! I just got my 2SD1071’s, replaced the BD649 in my circuit and now I have NO FIRE?

[mercuryman]

Ken W + I have connected the BC 337 up the correct way and no fire, I am using the 2SD1071 . Why did you change to the 2SD1071 if the BD649 worked.

[ken-w]

The 2SD1071 is rated at 400v instead of 100v, I was hoping that the higher voltage would have better longgevity.

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