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Thread: Negative Voltages: are they bypassable?

  1. #1
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    Aug 2002
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    South Australia
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    Negative Voltages: are they bypassable?

    I am building my own mp3 player, and I am opting to use linear voltage regulators as I find the cost of inverter solutions too high.

    My player is an old p1-75mhz with 4MB of ram and a 1gig drive for storage. It works well on my benchtop but I am now starting the move over to my car (1982 ;-) Daihatsu Charade ETX hatchback).

    The power needs are minimal, 3A on 5V, 1A on 12V so there will be minimal heat emitted from the positive regulators.
    ~20-50ma on -5V & -12V, it appears the motherboard is doing something with the negative voltages but I don't know what.

    I can't get the motherboard to boot without the -5V & -12V lines. Can some one tell me how to create -12V from +12V so I can feed it to a 7912 & 7905 regulator pair. Preferably using cheap, available, common components.

    Thanks in advance!

  2. #2
    Retired Admin Aaron Cake's Avatar
    Join Date
    Jan 2000
    Location
    London, Ontario, Canada
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    2,464
    A search should yeild a "real" answer, but the short answer is that there are no cheap and easy ways to do it. You will need to build a DC-DC converter to provide those voltages, or buy something from http://www.arisecomputer.com
    Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
    Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
    "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

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