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Can I take something that runs on AA batteries and...

Discussion in 'General Electronics' started by bigbossfan80, May 6, 2004.

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  1. bigbossfan80

    bigbossfan80 Guest

    I am curious as to whether or not the following is possible...

    I have some called an AutoXray for my car. It's a hand-held scanner
    that plugs into my OBD port and tells me various data parameters via
    my cars on-board computer. It's hand-held and runs on 4 "AA"

    Now, because I like doing a lot of custom things with my car,
    especially the interior, what I am wanting to do is take the AutoXray
    apart and fabricate it into my dash permanately. I have found that
    this will be quite simple other than the fact that I don't want to
    always have to be replacing the 4 "AA" batteries. I want to make it
    so that it runs off the cars power.

    From what I've researched already, I think all I need to do is buy one
    of those 12 to 6 volt adapters that they sell at Radio Shack, and wire
    it into the AutoXray. Am I correct in assuming this? The only thing
    that sucks is that the AutoXray ONLY can be powered with 4 "AA"
    batteries and doesn't have an input for an adapter plug. But I'm
    assuming that if I just do some re-wiring, I can get it work

    Anyone here have any input for me?

  2. Budwich

    Budwich Guest

    Yep... just cut the end off (6v side)... strip the wires and run them into
    point where 4 aa cells are connnected (dremel a small hole thru the case).
    Used a multimeter to make sure you get the polarity right. Do this all the
    time for all kinds of battery equipment that is used in non-portable
  3. Externet

    Externet Guest

    Yes, you can. Buy a 7806 voltage regulator integrated circuit, $1,
    it's the size of a dime. You connect it to +12V on one pin and another
    pin gives you +6 V.
    Even a 7805 regulator should work, as the device should be capable of
    working fine with not new batteries at 5 V.
  4. Unless you car is very, very old the minus of the car battery has been
    connected to the chassis. First make sure that the minus of the AA battery
    box is also connected to the cars chassis as well. If it is, you can use a
    common 12V to 6V converter. Be aware of the ground loop you introduce this
    way. It may or may not cause a problem.

    As for a adapter plug input you can mount one yourself into or near the lid
    of the battery box. Simple solder two pieces of wire from the input jack to
    the appropriate battery box contacts. (Use the wire side, not the
    batteryside of the box.) I ever made some fake batteries from a piece of
    round wood and connected the wires to a screwhead of a screw in the top and
    the bottom. This was mainly done not to modify the equipment to avoid
    warranty problems.

    petrus bitbyter
  5. gothika

    gothika Guest

    Sure, just wire the auto ac adapter directly into the rear contacts of
    your cigarette lighter and run the output wire into the AutoXray to
    the power contacts on the circuit board.
    Just be sure to keep the polarity correct.
    You might even panel mount the control module of the ac adapter to
    dashboard and mount a couple of dc coaxial jacks to power any other
    personal electronics you might have.
    I did this so I could use my mini cd-player in the car.
    I soldered in a mini stereo jack to my car stereo preamps and just
    jack in my walkman cd player for tunes.
  6. Byron A Jeff

    Byron A Jeff Guest

    -Yes, you can. Buy a 7806 voltage regulator integrated circuit, $1,
    -it's the size of a dime. You connect it to +12V on one pin and another
    -pin gives you +6 V.
    -Even a 7805 regulator should work, as the device should be capable of
    -working fine with not new batteries at 5 V.

    Just a couple of extra caveats:

    1) You can get closer to that 6V threshold by putting a diode between
    the 7805 ground leg and the car ground. This will raise the Vout to about 5.6V.

    2) You'll probably want to condition the input to the regulator. A running
    car is a noisy, nasty place from an electrical standpoint. Anything from hash
    to spikes in the hundreds of volts are possible. So suggestions:

    A) Use a current limiting power resistor in front of your regulator. That way
    in the event of a short or power surge, that a limited about of current
    reaches the regulator.

    B) Use a fuse, use a fuse, and use a fuse.

    C) Think about protecting your system with a power shunt even better, a crowbar
    that will slam the input voltage to ground and force the fuse to blow.

    With just a bit of protection, you can help your circuit from going up in

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