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Need 12 volt ac to 24 volt ac transformer

Discussion in 'Electronic Repair' started by [email protected], Apr 25, 2007.

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  1. Guest

    Hi I need to convert 12 volts ac to 24 volts ac for an outdoor
    lighting project low amperage, say 500 ma. I am looking for a small
    boosting transformer on the cheap. Any suggestions on where I can find
    something like this? Alternately I could use a cheap 12 volt ac to 24
    volt dc converter. Google has turned up endless garbage for me.

    Thanks
     
  2. me

    me Guest

    wrote in 4ax.com:
    Where are you getting your 12V? You could use a voltage doubler to get
    around 24 volts dc from your 12 volts ac...
     
  3. Arfa Daily

    Arfa Daily Guest

    Assuming that you don't need isolation, just use a tranny with either two
    12v secondaries, or one centre tapped 24v secondary, as an auto transformer.
    Connect the two windings in series ( if it's a centre tapped 24v winding,
    they already are anyway ), then connect your 12v AC across one of the
    windings. 24v will then appear across the pair of windings, so one leg will
    be common to both input and output. The primary would be unused, but it
    would be a good idea to just tie its ends together with a light load - say a
    10k resistor. you could connect a line voltage neon indicator across it as
    well, just to show that it's powered.

    Arfa
     
  4. Franc Zabkar

    Franc Zabkar Guest


    Here's a voltage doubling rectifier:

    D1
    o-----|--|>|-----|-----o +16V
    | _|_ +
    12VAC | --- C1
    rms | |
    o----- )---------+-----o 0V
    | _|_ +
    | --- C2
    | D2 |
    |--|<|-----|-----o -16V

    The unloaded output voltage is around 33V, but under load you may get
    closer to your target.

    - Franc Zabkar
     
  5. Tim

    Tim Guest

    OR you could get one of those 220 to 110 travel adaptors and wire the
    110 side to 12 VAC and get 24 VAC out the other side.

    - Tim -
     
  6. Guest


    Its for a 12 volt ac pathway lighting system (300 watt ac
    transformer). 2 or 3 of the lights I want to use are 24 volts.
     
  7. Guest


    That sounds the the perfect idea.

    Thanks
     
  8. They may have too much winding resistance. And of course, must be
    true transformers, not those triac things that are for hair dryers. ;)

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  9. Arfa Daily

    Arfa Daily Guest

    I rather think not, as the power rating of such an item is highly unlikely
    to be anywhere near the 300 watts or so that you require. At 24 volts, that
    equates to more than 12 amps ...

    Arfa
     
  10. Tim

    Tim Guest

    300 Watts? He said 500ma right? 24V x .5A = 12W (roughly)

    - Tim -
     
  11. Tim

    Tim Guest

    A real converter is just a transformer. We always use 'em backwards to
    step up voltages for our toys. I know that some newer ones may use
    semi's to do the job, but I did not suggest that type be used.

    - Tim -
     

  12. You also didn't warn him that if he chose the wrong type it would go
    up in flames.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  13. Guest


    Yep 500 ma (actually the transformer supplied say 800 ma) for some 24
    volt rice lights. I purchased some converters on ebay for 6.75 (doubt
    they are anything more than transformers) 50 watts each plenty for my
    app.

    Thanks
     
  14. Arfa Daily

    Arfa Daily Guest

    Indeed. I think I mis-understood his second post where he was talking about
    the actual lamps that he intended to use and the - quote - " (300 watt ac
    transformer) " I wrongly assumed that as he was talking about 12v and 24v
    lamps, and that the 12v ones had a 300 watt transformer to power them, we
    must have been talking halogens at 20 or 50 watts apiece. If the (few) 24v
    ones only require 500mA, then a transformer-based 'power converter', as you
    suggest, would certainly do the job. Sorry for any confusion.

    Arfa
     
  15. ian field

    ian field Guest

    Most decent transformer manufacturers supply transformers with 2 primaries &
    2 secondaries to make the transformer as versatile as possible.

    The primaries (which you don't need for what you want to do) can be in
    series for 230V and parallel for 115V, the secondaries can also be used in
    the same way so get 12V secondaries and wire them in series and use them as
    a 12V to 24V auto transformer.
     
  16. Radio Shack.
     
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