i built a test box to test electronic dashboards on countax mowers but need help

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  • petehall347
    Badcaps Legend
    • Jan 2015
    • 4423
    • United Kingdom

    #1

    i built a test box to test electronic dashboards on countax mowers but need help

    ok so i built a box to test the electronic dashboards on countax ride on mowers , all works fine and can test all functions with the aid of switches buttons and lights . only thing is the engine rpm that i cant check so need some sort of oscillator i can put together with parts from my stock . and need confirmation where to connect it to on the board . engine kill is short to ground and with it being connected to the coil i presume the signal comes from there .
    thinking will need 1000 to 3000 rpm variable .
    will post pics of my build later .
  • stj
    Great Sage 齊天大聖
    • Dec 2009
    • 30932
    • Albion

    #2
    Re: i built a test box but need help

    never presume - scope a mower if you can.

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    • petehall347
      Badcaps Legend
      • Jan 2015
      • 4423
      • United Kingdom

      #3
      Re: i built a test box but need help

      it has to come from the coil . i know you can program these boards for 1 or 2 cylinder engines .. if it came from the alternator it wouldn't matter . i could do with an oscillator that equates to between 1000 and 3000 rpm . i dont know what frequency it relates to .
      ok i worked it out i think .. 16.66 hz to 50hz .. but its 4 stroke so those figures need dividing by 4 . or does it need multiplying by 4 ?
      Last edited by petehall347; 07-25-2023, 06:11 PM.

      Comment

      • redwire
        Badcaps Legend
        • Dec 2010
        • 3900
        • Canada

        #4
        Re: i built a test box but need help

        3,000 RPM 2 cyl, 4 stroke is 50Hz at the coil
        1,000 RPM 2 cyl, 4 stroke is 16.7Hz at the coil.

        Assuming it's not a "wasted spark" ignition system that uses one coil with two HV outputs for 2 cylinders. Or maybe this is a magneto system?

        You can make an oscillator with a 555 or a couple transistors but most tachs are looking for a HV spike or several hundred volts to trigger, not 12V pulses.
        So you'd need to add an inductor to make the HV spike.

        Comment

        • petehall347
          Badcaps Legend
          • Jan 2015
          • 4423
          • United Kingdom

          #5
          Re: i built a test box but need help

          i expect the safest way is to try low voltage spikes first and see if it works . no way i want to probe a coil with my multimeter as have killed them this way . taking my scope to one isnt going to happen . i could take a spare scope that might not even work as has been left not used for years .saying that my bench one hasn't seen power for a long time .
          will see if i can trace the route to the mcu from where the signal goes to the board

          Comment

          • petehall347
            Badcaps Legend
            • Jan 2015
            • 4423
            • United Kingdom

            #6
            Re: i built a test box but need help

            ok as promised a couple of bad pictures .. ignore the rough and ready look .its a prototype
            Attached Files

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            • stj
              Great Sage 齊天大聖
              • Dec 2009
              • 30932
              • Albion

              #7
              Re: i built a test box but need help

              lol - thats quite a mix of led mounts
              have to start calling you Mustie2 if your gonna make a thing of small engine repair

              Comment

              • petehall347
                Badcaps Legend
                • Jan 2015
                • 4423
                • United Kingdom

                #8
                Re: i built a test box but need help

                everything apart from a dc socket that i bought is from what i had lying around here that i got off freecycle and all brand new in packets . as far as i know its the only oms diagnostic box in existence . oms is onboard management system . its made my job loads easier . next upgrade will be a 16 pin socket so i can then make the various leads for other boards . thinking of using car obd stuff for that .

                Comment

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