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Thread: Old G-Tech + junk = loggable accelerometer

  1. #1
    Senior Tuner
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    Old G-Tech + junk = loggable accelerometer

    One old style (red LED, no video) G-Tech
    One 9V battery clip
    One 1Kohm resistor

    Remove plug from cig lighter cable. Open case. Detach
    red wire of cig cable from its solder land. Attach red
    battery clip lead to this instead. Attach black battery
    lead to ground land (white wire, leave it too). Attach
    red cig cable wire to a 1K resistor, other end of resistor
    solder against Pin 12 of the ADXL105 chip. That's third
    pin from the top with the blue capacitors to the right.
    You need a fine soldering tip, 50 mil pitch leads.

    Now your cig lighter cable has white wire = ground, red
    is 0.5V - 4.5V output for -1G - +1G and you still have
    the digital readout. Ready for prime time. Tin the ends
    and screw 'em down to your MPVI plug.

    If you have the old style G-Tech laying around this is
    as close to a freebie as you can get. Took me about
    10 minutes (not including reading the datasheet for
    the part I found inside).

  2. #2
    Tuner in Training
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    That's freaking sweet!!! I knew the old G-tech would be good for something.
    1998 Camaro SS

  3. #3
    Senior Tuner
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    Here are a couple of pics which show the little bit of work needed

  4. #4
    Супер Модератор EC_Tune's Avatar
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    Jimmy, does it need the 9V or can it run off vehicle power?
    Always Support Our Troops!

  5. #5
    Senior Tuner
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    It could be left to run off the cig lighter and just bring out
    the single wire to the MPVI but I have this thing about
    ground loop errors... though with the relatively large signal
    maybe not a real issue. I just prefer to float the thing and
    remove all doubt. Same thing with the other box I built,
    that one also has two floating instrumentation amps to
    use with chassis-referenced sensors like wideband O2
    meters.

    But anyway, if you want the easiest way, just pigtail
    it from the point shown and take your (V-2.50)/2 g.

  6. #6
    Advanced Tuner TiredGXP's Avatar
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    Interesting project, thanks for sharing.

    I have a newer G-tech, so probably won't try this, but lots of venicles are now equiped with onboard accelerometers, I wonder if there is any way to access the signal from the onboard unit so you can log results - in my vehicle the DIC only displays peak acceleration, and only when speed drops below 7kmh. Note to self: Might be time to invest in the service manual and trace some wiring.

    2005 Grand Prix GXP - 5.3 LS4 - HP Tuned, MF catback, 1.8 rockers, K&N, Some day I'll finish putting the LS6 intake on

  7. #7
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    It might be worth popping the cover off the newer G-Tech,
    it has to have an IC accelerometer in there somewhere that
    can be similarly tapped (new one probably has a 2-axis one
    but I'm sure the datasheet can be found). Figure the same
    with whatever box in your car has the acceleration function.

    But I'd rather mung a $40 old GTech than something I'd have
    to replace at dealership prices.