High-Voltage Interface Needed

[captainkirksdog]

Hi,
Anyone got a high-voltage interface for inputing an automobile engine spark signal to an O-scope? I built a 4-to-1 multiplexer that lets me see 4 signals on each channel and I think it will make a good engine analyzer. Any ideas?

p.s.--It has to run at CMOS levels.

 

[Gene]

Maybe you could use the current running through your high tension spark plug wires to illuminate a neon bulb by induction. The lighting of the neon bulbs could be sensed by a photonic (Cds, photo diode, etc.) which could trigger your sensor. Since there is no connection to the spark plug wire (induction) and your neon bulbs are not connected to the photonic, you would have a signal without a wired connection. That way you don't have to deal with the high current. I would drill a hole through a dowel with the neon bulb stuck in one end and the photonic device stuck in the other end to eliminate stray light from hitting the photocell.

It's just an idea...

 

[Phasor]

I would try using an opto-isolator...

 

[Sebi]

Just wrap 4...5 turns to ignition cable outside.