Maker Pro
Maker Pro

Designing a circuit to sample magneto ignition signal.

dandy1

Jan 26, 2020
3
Joined
Jan 26, 2020
Messages
3
I want to capture the signal from a magneto ignition to interpret the rpm of a small engine.

with reference to this thread: https://www.electronicspoint.com/forums/threads/magneto-kill-terminal.288631/ these are the types of ignitions which are common on small engines.

and this output:
(courtesy of Debe)
wipac-pos-2-jpg.41360

this is not my output but illustration for what I am looking to achieve.


I am trying out this circuit:

Ign1.GIF

which works with some conditioning in software but there is a lot of noise encountered on the signal line which is totally erratic.

Its a bit hit and miss because the software is implemented to ignore pulses shorter than
X and longer than Y to avoid the erroneous readings which really limits the bandwidth at which i want to sample: 600-6000 RPM or 10-100 Hz.

On the other hand sometimes the circuit completely misses a pulse so at 3000 RPM i will get a reading of 1500,

I use this circuit because it is really simple and I want it to be compact. But I am willing to bet there is better way to do do it, maybe with better spec'd components or a different circuit altogether?

ideally i would also like to implement some filtering too, I've tried out some caps before and on the signal line but really that is a step beyond what i understand about electronics.

Any advice much appreciated

A
 

debe

Oct 15, 2011
278
Joined
Oct 15, 2011
Messages
278
They are $13 Australian & they are all you need if you want engine RPM & hours run.
 
Top