Small 120vac to 12vdc transformer

Discussion in 'General Electronics Chat' started by bd525, Feb 22, 2010.

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  1. bd525

    bd525 Thread Starter New Member

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    What is the smallest transformer (step down) that I can use to take 120VAC to 12VDC? I have project that needs 12vdc, but I am told as one of the requirements is not to use a standard wall wart transformer... Can I use a miniature PCB transmformer? Is there a better way to do this?

    Thanks!
  2. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    How much current do you need?
  3. bd525

    bd525 Thread Starter New Member

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    about 50mA
  4. t06afre

    t06afre AAC Fanatic!

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    Is this a school project? Because perhaps then your teacher want you to build a simple power supply as part of the learning process. A simple power is made by a transformer,rectifier, filter cap, and linear regulator(s).
    Also do not feel afraid to admit that it is a school project. You are welcome to ask your questions here in this forum
  5. KMoffett

    KMoffett Senior Member

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  6. bd525

    bd525 Thread Starter New Member

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    Hey Guys,
    Thanks for all your replies!!

    No this isnt a school project. I have been playing with electronics as a hobby and one of my personal projects caught wind of my boss and now had become part of a work project. I am learning as I do this so thats why I am asking questions here to get expert input.

    I will check out the link here in a few.
  7. bd525

    bd525 Thread Starter New Member

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    Thanks for the KMoffet, that might work... also I am going to start hunting some wall warts to see what I can find...
  8. KMoffett

    KMoffett Senior Member

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    If you are going to build this device for your employer, I would suggest you not go with cannibalized parts (wall-warts).

    Ken
  9. Audioguru

    Audioguru New Member

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    A cheap wall-wart AC-DC adapter has horrible voltage regulation. its output might be 12V with lots of ripple at its rated load current but might have an output voltage of 24VDC at a low current.
  10. bd525

    bd525 Thread Starter New Member

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    Thanks for the warnings guys, I will take your advice and only use the junk parts for my own testing...
  11. jls667

    jls667 Member

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    Although this is an old thread, I am looking to build or buy a transformer from 120vac to 12vdc. It would need to be relatively small to fit in an outdoor project box. It would need to run a few relays, so it only needs about 100mA. Any ideas?
  12. KMoffett

    KMoffett Senior Member

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    Check thrift stores or your friends' junk drawers. Orphan wall plug charger transformers will likely serve your purpose. It they are a little too big, I just "carefully" cut off the plastic case off.

    Ken
  13. MaxHeadRoom

    MaxHeadRoom Well-Known Member

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    If it is just for relays then presumably you do not really need regulated?
    As already mentioned, the older wall warts are unregulated, so don't go by the voltage stated on the cover, the O.C. voltage is usually 60% higher.
    You can usually tell them apart by the weight, the older ones have a 50/60 hz mains transformer rather than regulated switching supply.
    Regulated wall wart supplies can be had for around $5.00 now, so often it is not worth the effort to make for this size.
    Max.
  14. jls667

    jls667 Member

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    I am not sure how important a regulated supply would be to relays. My relays are 12vdc relays, but they are switching 120vac 7amp motor.
  15. szhighstar

    szhighstar New Member

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    slect EE13 or similar confirguration
  16. szhighstar

    szhighstar New Member

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    Location:
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    select EE13 or similar configuration
  17. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    What has happened here is called hijacking. A thread belongs to the OP (original poster). Hijacking is not allowed at AAC. Please start your own thread.
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