Converting a four wire tacho (current driven) to an electronic tacho

[alhbln]

As part of my switch to a Megajolt ignition i build a small electronic circuit to convert the "four wire" current driven Datsun tacho in my '72 240Z into an electronic tacho, which can directly be connected to the tacho output of the Megajolt, MSD, Bosch, Crane or other electronic ignition.

Quite surprisingly, the 38 year old tacho was very precise after a calibration, with the highest display error below 3%.

You'll find a complete description including the wiring diagram, pcb files and images here:

http://www.dinoplex.org/tachoconversion/

Best,

Adrian

[Twentysixouncer]

Awesome job. Thanks for sharing.

[alhbln]

I've set up a new project which contains a full replacement of the existing board. It is as simple to build as my previous conversion but is based on standard components and does not require an attiny programmer or programming software anymore.

The old project is now deprecated, the new one can be found at the same link: http://www.dinoplex.org/tachoconversion/

Enjoy,

Adrian

Edited December 21, 2012 by alhbln
added picture of converted 240Z tach

[SteveJ]

Thank you. I have been searching online about how to build a tachometer. I even have an old one to play with.

By the way, would you mind if I host your write-up on my blog, too?

[alhbln]

By the way, would you mind if I host your write-up on my blog, too?

Sure, but please keep the reference to my website

[SteveJ]

Of course, I would be more than happy to do so.

[240260280z]

Nice stuff!

[madkaw]

Adrian,

I would very much like to do this project, but I might need some help .I have a buddy that will make the circuit board for me, but I will need guidance installing it. I would document everything with pics and add to this thread with your permission. I already noticed that my 71 tach looks slightly different, but I might not know what I am looking at