How do Atom Computer Ignition modules work?

[debe]

JoeCB it is in the circuit diagram as a diode, its not in the original photo of the parts as it was found necessary mutch later in my trials. It has taken a couple of years of trial & error to get the module to this stage of reliability. The biggest problem was finding a switching transistor that was a Darington type with sufficient gain & voltage plus capable of at least 6amp pulses. The protector diode came about as some ignition coils give too high a voltage spike, this would either damage the transistor or over heat it & cause it to shut down. Ken W I don’t think going to a lower voltage would help with a Nova module, It just wouldn’t work at all once you put the diode across it, & I tried it with both polarity. I wouldn’t have got this far if I hadn’t sacrificed a perfectly good Atom module to find the actual value of the resistors & the capacitor. The circuit came from the US Patent of the module, but theres no values given in the Patent. If any one wants to read about the module look up (US Patent 4,163,437 Aug 7 1979) Invented by 2 Australians. Probably one of the reasons they stoped making them in 2005 was most small engines now use CDI ignition & lack of sales.

[phil-b]

Debe,

Another patent from the same inventors in US 4,911,126 (Mar 1990)
The table at column 9, line 40 claims higher output voltage ("circuit 5") with the addition of a diode.

Have you ever tested that out?

[mercuryman]

DEBE, What is the minimum voltage rating for the . 47 uf capacitor. I want to keep it small.

[chris-p]

Debe,

Just a thought, but have you ever considered selling these to the members that are not capable or making one, or understanding 80 percent of these posts, lol.

[legendre]

I’m not Debe, but..

quote mercuryman:

DEBE, What is the minimum voltage rating for the . 47 uf capacitor. I want to keep it small.

That cap is fed from a 4:1 voltage divider, which is connected across the coil primary winding. So, the highest voltage the cap will see would be 25% of the maximum voltage developed across the primary during the flyback phase. An educated guess would put that voltage at ~400V, so the cap needs to withstand 100V +20% safety margin – call it 120V.

However, he’s also using that transient suppressor diode across the primary, which IIRC clamps at 275V – so it +may+ be that the max. primary voltage is.. ~275V. In this case, the cap could be ~70V +20% margin, or ~83V.

So you should be safe with 120V in any case, and as low as 83V with a 275V clamping diode.

[jeff-register]

Legondre,
My thoughts would be the zener would cap the voltage being input? Just my uneducated calculationed guess!

[debe]

The capacitor I used was 100V as it was pretty small. The voltage across it cant be very high, as the max voltage the BC337 transistor can handle betwean Base/Emmiter (Vebo) is 5V. And Collector/Emmiter (Vceo) is 45V.

[legendre]

quote debe:

The capacitor I used was 100V as it was pretty small. The voltage across it cant be very high, as the max voltage the BC337 transistor can handle betwean Base/Emmiter (Vebo) is 5V. And Collector/Emmiter (Vceo) is 45V.

Yeah.. and if any of us had been observant enough to notice, the cap pictured on p.1 is marked for 100V,

Probably could have saved a bit of guessing & figuring.. I guess. 😉

[weedlessdrive]

Will these modules work on 1930’s opposed twin cylinder models with single coil?

[debe]

Only way to find out is try one.

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