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

  1. #1
    Registered Ign/ECU Nurse alhbln's Avatar
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    Default Converting a four wire tacho (current driven) to an electronic tacho

    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
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  2. #2
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    Awesome job. Thanks for sharing.

  3. #3
    Registered Ign/ECU Nurse alhbln's Avatar
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    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
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    Last edited by alhbln; 12-21-2012 at 12:00 PM. Reason: added picture of converted 240Z tach

  4. #4
    No more body roll! SteveJ's Avatar
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    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?
    73 240Z
    74 260Z

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  5. #5
    Registered Ign/ECU Nurse alhbln's Avatar
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    Quote Originally Posted by SteveJ View Post
    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

  6. #6
    No more body roll! SteveJ's Avatar
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    Of course, I would be more than happy to do so.
    73 240Z
    74 260Z

    Blue's collection of tech tips - A great place to look for answers
    XenonS30 -The cheap source for FSMs
    Georgia Z Club
    Fiddling with Z Cars - Z car tips & tricks and pictures of my car-loving life.
    Steve's CARtography - Just car pictures.

  7. #7
    Nova Scotia,Canada,Earth Blue's Avatar
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    Nice stuff!
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  8. #8
    Registered User madkaw's Avatar
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    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
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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