Fuel only using coil negative as tach input

[newtyres1]

Can the Microsquirt optoin+ be used with a coil negative input as the tach signal? I would think a 24V zener would be required as per V3.0 schematics note 3, is this correct? Would R20 being 680 ohms be OK, and will C27 and C28 be OK if left in the circuit? I cannot find a reference to this type of setup in the docs, hence the request for clarification.

Ian.

[Matt Cramer]

It can. The zener diode is a good idea but not all systems require it.

[kib_norway]

Working on a fuel only setup on a HD sportster, and wonder what to do with the tach/trigger signal.

I have an aftermarket ignition system that has a "Tach output" that is connected to an aftermarket tach. I guess this gives one pulse per rotation of the engine (v-twin).

How can I use this tach signal to trigger microsquirt?

Can I just hook it up to the pin 30 optoin1+ ?
And, what should I then do with pin 31 optoin1- ? Connect it to ground?

Happy if anyone can help... been working on this project since easter, and getting close to connect everything together now....

[Matt Cramer]

Kib_Norway, sounds like your proposed setup would work just fine. Wire the output to OPTOIN+ and ground OPTOIN-.

[kib_norway]

Hi,
Thanks for fast reply - will try this, and post results within a few days when everything is hooked up and ready to test.

kib_norway

[Bruce Bowling]

Can the Microsquirt optoin+ be used with a coil negative input as the tach signal? I would think a 24V zener would be required as per V3.0 schematics note 3, is this correct? Would R20 being 680 ohms be OK, and will C27 and C28 be OK if left in the circuit? I cannot find a reference to this type of setup in the docs, hence the request for clarification.

Ian.

We are looking at an alternative way to wire up the opto for triggering from ignition coil negative terminal. This setup uses the flyback energy to trigger the opto circuit.

Its easy to wire up - hook the opto+ wire to the negative coil terminal. For the opto- wire, hook this up to +12V battery thru a 4.7K resistor (instead of grounding it). Do not use a zener diode.

This keeps the opt turned off, only coming on when there is the ignition flyback pulse.

- Bruce

[A2TURBO]

Bruce I tried this and the unit suffered serious rests and was undrivable so far the best setup is my original Optoin+ to neg coil through a 10K resistor and Optoin- to chassis ground. it still has occasional resets but they usually donteven activate wue or ase. is there another setup you would like me to try? Im currently using my original setup and continuing with the tunning process (I got a good table it just a little to richon top)

[tech3sandcars]

I also have same question, my ignition says it puts out a 12v signal, 2 pulses per revolution. I think my hook-up is straight forward, tach to Optin+, ground the Optin-. What about the set-up in Megatune so that the right RPMs are calculated, do I set the teeth per revolution to "2"??

thanks

[kib_norway]

Kib_Norway, sounds like your proposed setup would work just fine. Wire the output to OPTOIN+ and ground OPTOIN-.

Update:

Optoin1+ to tach signal from ignition system
Optoin1- to gnd

Works excellent in my fuel only setup.

[Bruce Bowling]

Bruce I tried this and the unit suffered serious rests and was undrivable so far the best setup is my original Optoin+ to neg coil through a 10K resistor and Optoin- to chassis ground. it still has occasional resets but they usually donteven activate wue or ase. is there another setup you would like me to try? Im currently using my original setup and continuing with the tunning process (I got a good table it just a little to richon top)

When you say you have resets - is this processor resets or ignition resets? The opto input is totally isolated from the rest of the microsquirt circuit, so if you are getting processor resets then I suspect there is something else going on...

You can tell a processor reset because the time counter resets to 0 seconds.

- Bruce