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Suzuki speedo electronics

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  • Suzuki speedo electronics

    So I'm adding a vacuum drive cruise control to the bus at some point. It features a two wire sensor for magnets on a car's tailshaft.

    Bike has the standard new zook speedo hall effect sensor on the front sprocket.

    What I'd LIKE to do is wire the cruise unit into the existing sensor so I don't have to fuck about with extra magnets, sensor mounts etc etc etc.

    At the same time I might actually put a speedo healer in.

    But does anyone have (or know someone who has) any info on what the three leads do, the expected signal characteristics and loading ability of the sensor?

    I'm guessing it's Vcc, Gnd and signal - but not sure whether I can get away with parallelling off the signal line...
    "Once upon a time we would obey in public, but in private we would be cynical; today, we announce cynicism, but in private we obey."

  • #2
    In theory this is fine to do although if you want to drive separate units from the same sensor you may need 2 diodes which "Y" off of the sensor sig lead to each units sig input. You may need to experiment with this as most diodes will have a 0.7 volt drop across them to flow in normal direction. This "could" but probably won't rob the signal pulse of enough volts to make a legimate pulse to be recognized by either unit.

    Hope this helps.
    Adam

    "Light travel's faster than sound, that's why some people appear bright until you hear them speak."

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    • #3
      Thanks, Adam.

      I guess I need to hook the CRO on and see what's doing what with the thing on the paddock stand.

      Hall effect sensors are typically a three wire device, which concerns me somewhat coz the cruise unit only has two. I have a vague suspicion it's only a coil, but will have to pop the case on the controller to find out.

      Or just plug the fucker in and see what happens :o
      "Once upon a time we would obey in public, but in private we would be cynical; today, we announce cynicism, but in private we obey."

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      • #4
        Originally posted by Captain Starfish View Post
        I have a vague suspicion it's only a coil, but will have to pop the case on the controller to find out.
        Or just measure the inductance...

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        • #5
          don't have an inductomomomometer.
          can't be arsed making an oscillator and doing the frequency count thing.
          don't know the strength of the magnets.
          so don't know the expected current swing as the magnet passes the sensor.
          don't know the two input impedance of the sensor connector on the controller.
          so couldn't guess the expected voltage swing as the magnet passes the sensor.

          Hmmmmm....
          "Once upon a time we would obey in public, but in private we would be cynical; today, we announce cynicism, but in private we obey."

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          • #6
            Ok, so not directly applicable to Suzuki's, but the Honda wiring diagram from the VFR speed sensor shows that it is a pulse generator unit that wires up to the instrument cluster.

            Looking at where the 3 wires run, it would indeed be Vcc, GND & Sig if you have a similar unit.

            The catch is making sure the CC unit can handle the input from the speedo sensor.

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            • #7
              Ahh, isn't it funny the way the process of formulating a request for help yields the answer 9 times out of 10?

              Cracked open the cruise control case this afternoon and, after removing all the glue etc, managed to trace one wire to ground. The other one goes through a DC blocking series cap, then through a resistive voltage divider, past a clamping diode and into a tranny which is configured as an inverting squarer-upperer.

              Short version of the story - with all that crap in front of the processor I could pretty much feed it with 240V mains and it will still extract a signal. Well, not quite, but it's fairly rugged. And the cap followed by 150k resistor divider as first thing the signal sees means high input impedance (I guess you need that to derive a decent voltage from a current source like the coil pickup) which means it should be fairly invisible to the bike electrics.

              Yay!

              Thanks for your helpful input, folks.
              "Once upon a time we would obey in public, but in private we would be cynical; today, we announce cynicism, but in private we obey."

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