[Diy_efi] Ignition Pickup

[Brian Dessent]

"marko.cosic" wrote:

> How big a series resistor would this need?

It depends on what the largest voltages on the primary side are.  You
said the coil was being charged by the full 12V, right?  I'd guess that
the inductive spikes might get as high as 75V, maybe more.  I'd figure
that the diode probably needs 10 - 20 mA and can take up to 50mA
spikes... so I'd start with maybe something in the 600 ohm range, and if
the diode gets hot or fries, try 1k or more.

> > Or, try a comparator with a resistive divider
> > network to attenuate the primary ignition signal by like 10:1.
> 
> Primary - the LT side of the coil, not the main spark?

Yes.  Or you could wrap a few turns of wire around the HV lead and run
that directly into the comparator.

Brian

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