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Thread: newbie power question

  1. #1
    Newbie averagewonder's Avatar
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    newbie power question

    ok so if im using one of the automotive specific power supplys like the M2-ATX-HV 140W Intelligent DC-DC PSU can i just connect the power and ground wires to the factory harness for the radio since im planning on taking out the head unit and just use my pc will this work or what.

  2. #2
    Raw Wave
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    If it handles the current and is switched (or not) appropriately, then yes.

    But I think most prefer a separate dedicated line (from the battery).

  3. #3
    Neither darque nor pervert DarquePervert's Avatar
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    I wouldn't recommend it, but it might work.
    The more reliable & safer method is to run a dedicated power line to the battery.
    Have you looked in the FAQ yet?
    How about the Wiki?



    Under normal circumstances, a signature would go here.

  4. #4
    MySQL Error soundman98's Avatar
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    i agree with both answers above, but wanted to add a couple points-- a lot of car makers today like to combine fuses for low draw items to try to save space and money, and use one larger fuse-- while some cars have a dedicated fuse for the radio, others don't, and on these cars, it can make it even more critical that you do not blow a fuse-- you could loose a semi-important vehicle function.

    the other issue with using the factory wire is the power draw-- can you be 100% that the power supply will not draw more than the factory radio, at any given time? the engineers specced the wire to only carry enough power for the factory radio, so any more, and you could still run into problems-- even more so if you decide to ever 'just get a larger fuse'.

    you will be running wire, and taking panels off any ways to install the pc, why not take an extra 20-30 minutes and do it right, so that you don't have to redo it in a week?

  5. #5
    Raw Wave
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    So AvWo (or is is "Mean" Winder LOL!).
    It looks like "we" are saying the same thing - use a dedicated wire (fused of course!).

    My answer was brief, but to expand....

    For my "standard" Alpine 3x45W CD-Radio, I ran a dedicated +12V from the battery.
    This is in part to minimise electrical supply noise, but also.....
    I consider currents around 10A & above (say 100W-120W) to be "heavy"; too heavy for switches and standard "economical" wiring.

    Hence a dedicated wire/cable unaffected by other loads to deliver "clean" power with minimal voltage drop (hence max power to the load).

    The above should also apply to a load like yours (up to 140W-170W?) except that you are probably wanting to prevent noise INTO the vehicle's electrics from the converter.

    Keep in mind that traditional headlights are often 2x55W = 110W for low beam alone, and few cars (these days) use 110W rated cable into the cabin through a switch and to the lights (ie, ~10 Amps). Instead a low-current switch is used that controls a remote relay. (If not, often relays are retrofitted to improve lighting.)

    FYI - My Alpine uses a heavy twin cable (figure-8) back to the battery for +12V & 0V, but the 0V (ground) may be overkill; but it was easier than worrying about a body ground.

  6. #6
    Newbie averagewonder's Avatar
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    thanks guy i guess my question is now if i connect the power directly to the battery and i ground do i put a switch to the power??? otherwise it seems like the carputer would not shut off when i turn off my car im missing something here right? what did you guess do to have your carputer come on automatically i would rather not hit a separate switch just to turn it on. please keep in mind im new to this

  7. #7
    MySQL Error soundman98's Avatar
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    "all your questions and more can be answered in the adv. faq"

    http://www.mp3car.com/vbulletin/advfaq.php

    (there is a 3rd wire-- a ignition line, that tells the power supply when to turn on/off)

  8. #8
    Raw Wave
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    I'll assume it's for battery status indication else a PC-initiated command to put the charger into stand-by. (The answer was not apparent on the linked page.)

    Whatever the reason you say you need it for determines what you used for your charger.
    (I don't see the need for either in a car situation assuming (1) it is not left there for long idle periods & (2) the PC battery does not depend on it for its protection.)

    So if the charger can not be exchanged or replaced, it's a suppression issue.
    Hence presumably conductor filtering.
    Else maybe aluminium foil etc.

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