Fuel Gauge Wiring?

Discussion in 'Australian Motorcycles' started by Nigel Allen, Jan 12, 2012.

  1. Nigel Allen

    Nigel Allen Guest


    Having got the ER5 back on the road last year, legal thanks to a bicycle
    speedo, my next job is to build an instrument cluster for it.

    The speedo is staying as is but I am going to (re-)fit idiot warning
    lights for left and right indicators, oil, water, neutral and high beam
    and maybe a rev counter.

    I've sourced all the bits I need from Jaycar, LEDs, resistors, mounts
    and a box to fit everything in.

    The sticking point is the fuel gauge - not a must-have, more of a
    nice-to-have (considering its rat-bikedness).

    The instruments were stripped off by a friend of mine who was staying
    with me and I cannot see any obvious electrical connections - certainly
    no spade connectors. There should be three connections according to the
    wiring diagram for pos, neg and sender.

    Here are some photographs I took of the gauge itself:


    Apologies for the point and click quality.

    Anyone care to hazard a guess as to connections? Or does the collective
    consciousness think there is something else missing.

    Nigel Allen, Jan 12, 2012
    1. Advertisements

  2. No need to apologise for the quality - it's the painful size (1.5Mb+ each)
    of the images which you should've taken care of :p
    There're three solder lugs that I can see; http://yak.net.au/t1/er5fuel.jpg

    I can't offer any suggestions as to which terminal is which though.

    Do you have a multimeter? If so, can you check the resistance between each
    of those points and post the results here? The ground terminal should be
    obvious, as it should have a dead short to the chassis of the gauge (this
    might even be possible to confirm visually).

    Failing that... Grab a 220 ohm resistor (to limit the current) and wire it
    in series with the battery positive, attach the battery negative to the
    gauge chassis, then start probing around the terminals until you get a
    needle deflection. Make sure to only touch each terminal for a second at a

    If you get a mild spark, you've found the ground terminal.

    If you get nothing at all, you've found the positive supply terminal.

    If you get a needle deflection, you've found the signal terminal.

    As an alternative (seeing as you're replacing all the other instruments
    anyway), you could get yourself an LM3914 and a string of 10 LEDs to give
    you a more modern display, in keeping with the new cluster.
    Bob Milutinovic, Jan 12, 2012
    1. Advertisements

  3. Nigel Allen

    Nigel Allen Guest

    Oh my goodness - something I tell every one of my customer's employees.
    Guilty as charged. Mea cupla mea culpa mea maxima culpa.
    Muy gracias Bob. I /do/ wish you hadn't told me about the LM3914 though
    - that's enough to take me off on another track entirely :)

    Nigel Allen, Jan 12, 2012
  4. Bob Milutinovic, Jan 12, 2012
  5. Bob Milutinovic, Jan 12, 2012
  6. Nigel Allen

    Nigel Allen Guest

    Nigel Allen, Jan 12, 2012
  7. Nigel Allen

    Nigel Allen Guest

    Nigel Allen, Jan 13, 2012
  8. Nigel Allen

    Nigel Allen Guest

    I just /know/ I shouldn't go down this path but.....

    Given you know just a little more than the average lurkler here, can you
    take a look at this:
    and tell me if that circuit would work with a twin cylinder machine? I'm
    kind of intrigued.

    Nigel Allen, Jan 14, 2012
  9. You mean, I finally get to put my electronics engineering degree to use?
    Whoa! 8-P

    The circuit'll work with any number of cylinders, because you're not trying
    to measure a precise value - merely a calibrated scale of 0%-100%. It's just
    a matter of adjusting the trimmer to suit the frequency range given out by
    your bike, so even in extreme cases (16 cylinders perhaps?) you'd only need
    to change a couple of components to compensate.

    There is though one major problem - visibility. If you use standard 8mCD
    LEDs, they'll look perfect at night but will be invisible in daylight (even
    on an overcast day). If on the other hand you use 500mCD LEDs so you can see
    them in daylight, you'll be blinded at night.

    You could of course implement a potentiometer or switch and resistors to
    manually adjust the current supplied to the display, but that'd be fiddly -
    or devise a light-sensitive automatic dimmer, but that'd be more costly.

    At a rough estimate of $75-$80 for parts (the semiconductors alone are
    nearly $37 from Jaycar) plus several hours of dicking around, I'd have to
    ask again, "is it worth it?" Sure it'd be a great adventure in
    doing-it-yourself and you'll have no end of self satisfaction when you get
    it working, but (1) you'll have much frustration in getting it to work (and
    look) the way you want, (2) it won't look professionally done, no matter how
    good you are with your hands, and (3) it is only a tachometer after all -
    you'll still need to build similar assemblies for the speedometer and fuel
    gauge (and potentially battery votage, current monitor, temperature monitor,
    etc., etc., etc...).

    I'd still go with a ready-made device (especially the $90 from China); given
    that it won't look like anything anyone else has on a similar bike, it'll
    have enough of the "uniqueness" you seek, and the time you spend connecting
    it properly and getting it to mount without falling off at the first corner
    will give you the "I did it myself" factor - and it'll have all the extra
    facilities, including an odometer and trip meter.
    Bob Milutinovic, Jan 14, 2012
  10. Nigel Allen

    DM Guest

    Nowadays you do that kind of thing with micro-controllers.
    Arduino is a popular one.
    DM, Jan 14, 2012
  11. Nigel Allen

    Peter Guest

    There is a tacho function on the trailtech voyager speedo I put on the
    DR650. There is a delay in this part of the system that makes its reading
    Basically, it is too slow... Even for me at the moment!
    Peter, Jan 14, 2012
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.