Go Down

Topic: RPM input circuit from coil (Read 1 time) previous topic - next topic


I want to build a RPM counter for my car using an Arduino.

The rpm signal need to be picked up from the negative side of the ignition coil.

Now I know there are some nasty spikes being generated.

I need help with a circuit diagram and components to be able to input the rpm signal to the Arduino without damaging it.



Thanx Magician,
I had a look at the link you posted.
Thay use an inductive pickup on the HT lead.

However I want to pick up the signal directlu from the negative side of the coil.

Any suggestions?


Use an optocoupler rated at 500V or more.  The - side of the coil spends most of it's life seeing 12v, to fire the coil the - side is pulled to ground for between 0.5ms and 4ms and then sent high again.
For your purposes detecting when the - post goes low will give you a nice trigger.  Wire the trigger side of the optocoupler so the internal LED grounds to the coil - post and receives power from a 12v source (with resistor, if needed).

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131