Another ignition pick-up sensor question (with a diagram)

Capt. Quirk

I recently replaced the stator on the msd ignition for the jet ski racer, it was a giant hassle
because the parts are no longer available. A few months later the control box failed.

I have been working on my own version of an ignition system using the propeller, and
since the other ignition system failed, I was thinking about using the stator sensors
from the other system to trigger my ignition system.

But I don't understand how the sensor works, because it does not seem to work like a
hall or reed switch.

The Control box provided a low voltage to the two wires that lead to the sensor. There
no grounds that I am aware of.

It is possible there is an smd choke coil inside the sensor with a concentration glued to the
top of the coil. If that is the case, could you power the choke with both wires? Or maybe
the 2 wires had pull up resistors inside the control box.

If both leads had pull-up resistors and they used a choke coil, how could the Propeller
sense a magnet as it passes by. It would create a sine wave right???

Would you use a LM339 comparator?

Thanks for your input.

DigitalBob

That MSD unit uses a magnetic pickup. I would hook up my oscilloscope to the trigger pickup then pass a magnet over it quickly. Monitor the signal and come up with a substitute . The pickup is probaly a piece of iron core with a coil around it. They use this style pickup on their big block crank trigger.

DigitalBob

Disconnect the pickup and measure the resistance with an ohmmeter it should be low 60-100 ohms.

DigitalBob

You can still buy these new from MSD for about $700 pn 42351

Capt. Quirk

I took me a few days to retest the stator, and it has continuity.

I know that MSD claims there is a coil in there, but from the two I am in the process
of tearing apart, there is no normal pick-up coil inside.

There is a small circuit board with a very small diameter sensor, that has a metal
cone on top of it. Allegro called it a concentrator.

Like I said before, it may have an smd choke coil inside with the concentrator mounted
on top. The sensor is about 3/16" in diameter.

Capt. Quirk wrote: »

But I don't understand how the sensor works, because it does not seem to work like a
hall or reed switch.

The Control box provided a low voltage to the two wires that lead to the sensor. There
no grounds that I am aware of.

If there is a really small pick-up coil inside, why does it require a small voltage on both
wires from the box to the sensor?


Bill M.

DigitalBob

It could be an allegro ATS685