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Thread: Powering CARPC - Wiring/Battery reboot

  1. #1
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    Powering CARPC - Wiring/Battery reboot

    Can anyone explain more specifically where to pull the power wires (12v constant, Ignition and Neutral) for my carPC?

    I have a Mazda 3 and I'm using a M4ATX psu but every time I crank the engine it reboots my PC and it's annoying the crap out of me.

    I'm thinking it's the wiring because I'm pulling the 12v and the Ignition power from the firewall under the glove box. But when I crank the engine I notice that I loose power to everything else in the car...

    So, does it matter where I pull the power from during engine crank? meaning... are there certain places where it cuts of the power during crank that I shouldn't use to power the CarPC? or is this a battery issue?

    -YACO

  2. #2
    Maximum Bitrate FusionFanatic's Avatar
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    sounds like you wired it wrong...

    the firewall is not a power source, I assume you are referring to the 'fusebox'. if that is the case then that's your problem right there. you are drawing your 12v constant power from a switched power source (and you're drawing from a source that cannot provide as much current as the M4-ATX may require).

    the M4-ATX ignition line should be connected to the car's ACC circuit or IGN circuit. it sounds like you already have this connected to an ACC line in your interior fuse box, if that is the case then you can leave it the way it is.

    12v constant power should be drawn from the car battery (or an unused slot in the power distribution center; if your car has one), not from the interior fusebox. this will require you to run a [fused] wire directly from the battery to your M4-ATX. the M4-ATX can draw up to 25A under full load. you should run 10awg (or thicker) wire for this.

    your ground wire should be the same gauge (or thicker) as your 12v constant wire, and should be as short as possible. run this wire to the closest [chassis] ground point to your carputer.

    once you correct your wiring, then it should work just fine. good luck

  3. #3
    Low Bitrate ZEEBEES's Avatar
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    Quote Originally Posted by FusionFanatic View Post
    sounds like you wired it wrong...



    12v constant power should be drawn from the car battery (or an unused slot in the power distribution center; if your car has one), not from the interior fusebox. this will require you to run a [fused] wire directly from the battery to your M4-ATX. the M4-ATX can draw up to 25A under full load. you should run 10awg (or thicker) wire for this.

    your ground wire should be the same gauge (or thicker) as your 12v constant wire, and should be as short as possible. run this wire to the closest [chassis] ground point to your carputer.

    once you correct your wiring, then it should work just fine. good luck
    exactly the problem I have been having, I debated attaching the red constant hot lead to battery but thought a constant hot source from interior fusebox with an add-a-fuse would be a cleaner solution. think I'll rewire to the battery with an inline fuse instead. I kept having the issue of computer shutting down about a minute after car shut down.

  4. #4
    Variable Bitrate billmee's Avatar
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    Quote Originally Posted by ZEEBEES View Post
    exactly the problem I have been having, I debated attaching the red constant hot lead to battery but thought a constant hot source from interior fusebox with an add-a-fuse would be a cleaner solution. think I'll rewire to the battery with an inline fuse instead. I kept having the issue of computer shutting down about a minute after car shut down.
    I use a connection to the interior fuse box but first checked to see that it was constant power. I personally don't see the need or want the hassle of connecting directly to the battery.


    The computer shutting down a minute after the car is shut down is probably a feature of the M4 not a problem.

  5. #5
    Neither darque nor pervert DarquePervert's Avatar
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    Onbe potential issue with using the fuze box is power draw. If you draw more power than the circuit can handle, then you're going to be blowing fuses constantly.
    The fuze box isnt' rated to handle circuits of more than 15 or 20A, typically.
    The M4 potentially can draw more than that amount.

    Sure, you could throw a higher-rated fuse into the circuit, but then you run the risk of damaging your quipment and the wiring from the amount of current.
    Can anyone say FIRE HAZARD?

    For your own safety, wire your equipment up the proper way. You'll enjoy the lack of frustration, as well as the safety of you, your ride, and your passengers.
    Have you looked in the FAQ yet?
    How about the Wiki?



    Under normal circumstances, a signature would go here.

  6. #6
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    Curious but I thought without a tank setup it would always shut off because of the draw from the starter. Which is why every other single electronic goes off when you start your car.

  7. #7
    Variable Bitrate billmee's Avatar
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    Quote Originally Posted by DarquePervert View Post
    Onbe potential issue with using the fuze box is power draw. If you draw more power than the circuit can handle, then you're going to be blowing fuses constantly.
    The fuze box isnt' rated to handle circuits of more than 15 or 20A, typically.
    The M4 potentially can draw more than that amount.

    Sure, you could throw a higher-rated fuse into the circuit, but then you run the risk of damaging your quipment and the wiring from the amount of current.
    Can anyone say FIRE HAZARD?

    For your own safety, wire your equipment up the proper way. You'll enjoy the lack of frustration, as well as the safety of you, your ride, and your passengers.
    I hear you dp.
    Dedicated fat wire fused at the battery is the gold standard.

    My point was if you pc's demand is within the existing wiring in your car why not use it. Having said that at any given time I have several meters including an dc clamp to see what that my pc is drawing 6 amps on a 15 amp fuse over 14 gauge wire. Six years original fuse.

  8. #8
    Neither darque nor pervert DarquePervert's Avatar
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    Quote Originally Posted by mdawg View Post
    Curious but I thought without a tank setup it would always shut off because of the draw from the starter. Which is why every other single electronic goes off when you start your car.
    The better DC-DC power supplies for PCs are able to survive cranking.
    Have you looked in the FAQ yet?
    How about the Wiki?



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  9. #9
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    ok... now I have a Mazda 3 07 and there's no easy way to pull a cable from the engine side (battery) through the inside of my car (carpc is under the passanger's seat).

    Did any of you have this issue? everything seems well sealed and i don't what to drill holes on my car...

    -YACO

  10. #10
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    Quote Originally Posted by YACO View Post
    ok... now I have a Mazda 3 07 and there's no easy way to pull a cable from the engine side (battery) through the inside of my car (carpc is under the passanger's seat).

    Did any of you have this issue? everything seems well sealed and i don't what to drill holes on my car...

    -YACO
    I had a similar issue, but I learned there is always a way to do it. The hardest part is finding a way to get power from the hood, to the cab of the car, but I have a pc under the driver's seat and managed to get it done.

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