Tachometer Bench Tester

[golfather]

Hello all

I want to build a tachometer bench tester for VW MK2 Golf tachometer. My understanding of the mk2 golf tachometer it is driven by the negative signal from the coil.

I have looked at the various sketches/circuits available on forum.

One idea was based from a car forum to use a relay coil as an inductor.

Any help or guidance would be appreciated.

Thank you

[paulpaulson]

Hello
Are you shure ?

[hammy]

Not sure why you would want to do this unless you are setting up a business to test tachos

Hmmm … the problem is , if it works with your relay , will it work on the car ? Maybe, maybe not …if it didn’t work is the tachometer faulty or your circuit ?

I think you need to be switching a real coil which needs a transistor that can stand the high voltage generated . If I was doing it I’d google “ electronic ignition”. - recall making transistorised ignition back in the 1970’s , but sure what I used back then

[johnwasser]

@golfather

Any help or guidance would be appreciated.

Have you tried the 'relay coil as inductor' and transistor switch method? Just hook it to an Arduino pin and use the 'tone(pin, frequency);' function to send it a test signal. I'm thinking any 12V relay coil will do.

[TomGeorge]

Hi,
Have you actually tried the circuit?

Tom...