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Transformer for 12v halogen lights

Discussion in 'Electronic Repair' started by Pete L, Feb 10, 2008.

  1. Pete L

    Pete L Guest

    I bought a box of three halogen kitchen lights. I need to split them
    into a two and a one for under the kitchen cabinets. To do this I'll
    need another 12v transformer. Do I need to get the same type or could
    I use any 12v transformer - even something for a radio or a battery?
     
  2. Baron

    Baron Guest

    I would certainly get the proper PSU for those lights. If yours are the
    same as mine, the so called transformer is actually a switch mode power
    supply with an un-rectified output at about 200Khz.
     
  3. Jim Yanik

    Jim Yanik Guest

    OTOH,12V is 12V,as long as the transformer can supply the 10 or 20 watts
    per bulb. the bulb doesn't care if it sees 60hz or 200Khz.

    It's just that the switchers are smaller,cheaper than ironcore xfmrs.
     
  4. Arfa Daily

    Arfa Daily Guest

    From what I've seen of the ones that I've bought for my house, sets of three
    tend to have a 'conventional' iron cored transformer, and sets of five have
    a little switching supply. Agreed with what Jim says. Any transformer will
    do that has the right rating. A 20 watt lamp would draw about 1.6ish amps,
    so that's what the transformer needs to be rated at as a minimum, for one
    bulb. If using a conventional transformer, don't go too much above that
    rating for a 12v type, as the voltage may be quite a bit higher than 12v, if
    the winding is loaded too lightly. This is why the makers of these lights
    recommend that a failed lamp is replaced at the earliest opportunity, to
    avoid over-running the ones that are left intact.

    Arfa
     
  5. Jim Yanik

    Jim Yanik Guest

    those little quartz halogen lamps are expensive,too.
     
  6. NewsGroups

    NewsGroups Guest


    Be sure that whatever you use is thermally protected and UL approved.
     
  7. Baron

    Baron Guest

    Whilst I agree 100% with you Jim. The reason that I made the comment is
    because the bulbs are quite sensitive to voltage and the "Electronic
    Transformers" do provide a fairly regulated output as long as they are
    used within max/min loading. Mine are rated at 60W max 20W min one to
    three 20W bulbs.
     
  8. You got good replies. I'll add that I've seen halogens run from AC
    with normal transformers and nothing else (50Hz), DC both linear and
    SMPSU, not to mention the varieties that run straight from 250VAC (in
    these parts). They all seem to work for their uses, more or less.

    One thing to note is that you might have an innocent looking 10W bulb
    but when you look at it, that 10W needs nearly 1A of current and if
    you have a few, you'll need several amps. A common wall wart won't
    quite cut it.

    I think the intended type SMPSU's should be relatively inexpensive and
    simple to wire, closed, approved, no changes needed and powerful enough
    for their rated loads. They might not start on too light a load, though.

    SMPS efficiency should also be very good as transformers go and their
    switching frequency, if it causes any visible change in the light which
    I think is unlikely, is higher so it's less likely to cause flicker
    effects.
     
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