Tach input from spark voltage (BEWARE!!!)

[hoss karoly]

Johnny wrote:
> 
> I know that's what we were taught in school, but I have never been able to
> "scope" anything near that high out of a simple points and coil system with
> a cap to ground on each post of the coil. I also don't understand the line
> below about the resister and zener bit. He wanted to use an inductive
> pickup to sense the ignition on the primary side, not attach to it
> directly.
> 
yeah I tend to believe what I was taught
but if the cap dies the voltage can be really high
I'd put an opto-coupler between my pic and the signs :)
bye
charley