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12-volt halogen-bulbs on Dell power supplies

Discussion in 'Electronic Basics' started by Tibur Waltson, Jan 25, 2004.

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  1. I'm trying to use three 12-volt 20-watt rail halogen bulbs.
    These bulbs will shine on paintings, kitchen cabinets and an
    armoire. Is it safe and efficient to use halogen bulbs with a 60-
    watt constant current computer power supply compare to a
    halogen transformer? Also, will the computer power supply
    work with a standard household 600-watt dimmer?

    TIA, Tibur
  2. w_tom

    w_tom Guest

    First, a computer power supply is constant voltage; not
    constant current. Second, computer power supply typically is
    rated at 60 watts distributed among the many voltages. 60
    watts not output by every voltage. Third, dimmer on power
    supply input will do nothing useful. It will only make a
    power supply test circuit. Either that power supply will
    output constant voltage, or it will shutdown. Dimmer on power
    supply input will not reduce voltage output. Forth, a 20 watt
    halogen may demand up to 100 some watts for a very short time
    when starting. How the power supplies foldback current
    limiting responds to this is a response unique to that power

    Question - does power supply output voltage even match
    voltage of halogens? Better, safer, and cheaper to power
    halogens from a transformer designed just for that purpose.
  3. Probably. The 12VDC bulbs will use 5A total. Computer power supplies will
    produce lots of amps at 12V. This one

    can produce 17A at 12V. You need to ensure that your computer power supply
    will supply more than the required 5A at 12V.

    Also, will the computer power supply
    Sadly, no. Dimmers work with things like lightbulbs by changing the AC
    waveform. Unfortunately, you computer power supply is undoubtedly a
    switchmode power supply, which will just freak out and misbehave if given
    this odd waveform. You can dim the lights at the bulb side by varying the
    voltage or 'duty cycle' into the DC bulbs (using a circuit between the power
    supply and the bulbs). Its not just a matter of buying something from your
    hardware store, however.

    Bob Monsen
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