De-twitching an electronic tachometer

Quick response, looks like you're using a NE555N as well. This behaviour works with the rather underdocumented difference between reset and trigger voltage input levels, manufacturers may well decide these are not worthwhile parameters to maintain between batches.

Most of my testing was done with an idealised 555 test signal, I can well believe that a noisier signal (e.g. Dyna with ringing at the switching point) might lead to less predictable output. I'm using a clean 12v tach signal from a prototype igniter.

I see what you mean with multiple voltage signals at shunting crossover, I guess you'd need some hysteresis at the threshold.
I'm not so convinced by the spikes on the last signal image, is this possibly an impedance matching issue with the scope probes?
Like I say, the stator signal seems to be a cleaner signal with less ringing at the switchover than does an IGBT-connected inductive coil voltage signal.
I had entirely forgotten about the number of poles on the stator, so the extra overhead of a frequency divider is a negative.

The one in the photo is a Ne555, but that is not necessarily what I used earlier. I've had that board cleared a few times with different projects in the interim. I have some old stock 555's rolling around in the parts box. The earlier steady-low could also have been a misinterpretation of the 22k/220k confusion.

I've had other issues with using the reset pin as a signal input in the past. I generally avoid it.

As far as the stator goes, I would assume the signal was slow enough that impedance mismatch wouldn't really cause the spikes, but I can't say for sure. It would be interesting to expand one of those spikes to see if it's a series of spikes or a single isolated spike.

Some things need some time and hardware to fix the problem.
I solve my bouncing rev meter needle/Dyna III problem with a signal converter.
I soldered a wire to one of the Dyna pick-ups on the backside.
Output is 0,50 - 0,80 Volts square wave with an oscilloscope detected.
The converter, (min. 0,10 Volt input square/sinus/triangular signal = ABS sensor), transforms the signal to a 12 Volt square signal,perfect for my KOSO RX2N+
What should i say it works like a puring cat!!!





Thank you a lot weeZee and loudhvx for the technical support and explanations.
Your both are great electronic master brains!!!

Michael

Glad it's working!

BTW, the rotor on your Dyna looks a little "fuzzy". Are those metal filing?
A good way to remove metal filings from a magnet is masking tape. I learned that trick on speaker magnets.

Thanks loudhvx

Your so called metal filing on the rotor are harmless grease marks, (i put some grease on the advancer).
A German proverb says grease good = drive good without problems.

Ahh

I have to replicate to you and weeZee, thank you for the technical support.

A very thankful Michael