Car speedo signal converter

Discussion in 'The Projects Forum' started by Nubaroo, May 29, 2011.

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  1. Nubaroo

    Thread Starter New Member

    May 28, 2011
    Hi guys.

    I am new to this forum and need some help please.

    I have some electronics knowlege - from 20 years ago LOL!

    I have recently changed my cars gearbox to a stronger type. However now I cannot use the same speedo drive anymore. I have been told to use an ABS sensor(magnetic type 2 wire) running and sensing from some metal "teeth" off the front CV-joint. I have mounted the sensor and get a fairly clean sinewave from it - approx. 400mV peak to peak only though, with the frequency going higher as the wheel speeds up. I will measure the frequency and advise.

    My speedo needs from what I can understand a 12V square wave to operate? So I need advice or preferrably a circuit that would use the cars 12V battery power supply to convert the 400mV sinewave to a useable 12V square wave??

    I have tried using an Op-Amp in the comparator configuration but for some reason this does not work....?? Maybe my circuit I pulled off the internet was not correct or I made an error building it LOL.

    I am now thinking of using a VF converter( Voltage to frequency) that I saw on the internet - NJM4151. This will take a 0-10V signal on the input and generate a 12V square wave 1HZ to 10KHZ on the output.

    My thoughts are to push the sinewave from the ABS sensor through a small bridge rectifier, and then to utilise the DC voltage derived from this into the VF converter. Surely the DC voltage should rise as the AC frequency rises as the car speed up, or would the generated DC voltage only be amplitude related - any thoughts about this??

    Any other suggestions would be greatly appreciated!

    Thanks in advance.

    Last edited: May 29, 2011
  2. bertus


    Apr 5, 2008

    I am closing this thread as it violates AAC policy and/or safety issues.

    6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:

    • Any kind of over-unity devices and systems
    • Automotive modifications
    • Devices designed to electrocute or shock another person
    • LEDs to mains
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    There will be enough sites where automotive questions can be discussed :
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