[fenderer]

I'd like to request hopefully what would be a simple upgrade to the Tacho output functionality to allow it to be usable with the wider range of aftermarket rev counters/ tachometers now available.

I'm running a 0.4.3d board (V8 wasted spark) with the latest firmware and I've run into some major stability problems driving such a typical aftermarket rev counter. I think most of this is down to the issues with 8 cylinders, lots of ignition events and the fact the tacho pulse can't be anymore than 3ms before the pulses start to overlap and the rev counter just drops to zero when over 4000rpm.

I'm using a modern 12v pulse driven stepper motor type rev counter (many thousands of units sold on eBay), it works fine on the bench using a 50% duty PWM signal with 15 pulses per 1000rpm. When I try to use it with Speeduino I only really have the choice of setting the tacho output pulse at 1ms or 2ms. But the pulse is too short to be recognised and is very susceptible to noise. The result is the rev counter is unusable and dances all over the place and won't even reliably display idle speeds at 1000rpm.

A 50% duty PWM cycle option would help stability at the lower end of rev range and would probably eliminate false positive triggers caused by electrical noise. It will also automatically reduce the pulse width higher in the rev range preventing the on pulse overlapping with the off time.

I have tested my own rev counter with a simple Arduino sketch that uses the 50% duty at 12v DC output and it works perfectly correlating with 15 pulses per 1000. 66.66Hz=1000rpm, 200Hz=3000rpm etc.

I have posted a video on YouTube (link below) showing testing a rev counter with the Arduino produced 50% duty signal.

https://youtu.be/BQOrvD-fzoU

Thanks for the consideration.

[N2_]

If I am understanding correctly you want the output pulses to be shorter in duration, A.K.A a narrow pulse. In other words, the option to set the pulse duration in milliseconds from its current 3ms down to 2ms or perhaps something even less.

[ArvillaKovacek]

I watched your video, although I don't understand much because I'm not very good at English, but I still wish you success.

[RempageR1]

If I am understanding correctly you want the output pulses to be shorter in duration, A.K.A a narrow pulse. In other words, the option to set the pulse duration in milliseconds from its current 3ms down to 2ms or perhaps something even less.

No the TS wants the pulses to be high 50% of the time and low 50% of the time, to get something like this:

zzz.png (3.81 KiB) Viewed 275 times

Which is what you see on the scope in the video.

[PSIG]

Tachometer function can be frustrating for many, without knowing the type of tachometer signal that is required. There are different types of tachometers for different signals. Current, flyback, logic PWM, etc.

I don't think that specific tachometer is designed to operate with a low-volt PWM signal. Doing a look at the advertisement, they are not specific, but their compatibility listings span from the 1960s and end at 1978, and so is likely intended for either current triggering, or more likely for flyback signal triggering.

That was all to put my question into context. Are you trying to find a way to make it work with low-volt PWM signals, or trying to make it work with the type of signals it was designed to use?

I have not seen nor know where to find the product instructions, which might further help to determine the correct signal type (beyond using ad clues), and therefore best function - if that's what you're after. An example of using a PWM-to-flyback signal adapter for testing can be found here.