Where To Get Transformer / Power Supply (US)

Discussion in 'General Electronics Chat' started by Go3Team, Aug 1, 2011.

  1. Go3Team

    Thread Starter New Member

    Aug 1, 2011
    I've been working on a IR LED lighting project. My prototype currently has a wall wort power supply enclosed in the weatherproof enclosure. I'm hoping to come across a more stable power supply that brings 120VAC to 12VDC @ 1 - 1.5 amps. Radio Shack has a Center Tap that has some pretty questionable reviews - Catalog #: 273-1352. I'm looking for something pretty reliable, as it will be mounted in a place pretty hard to get to, and I only want to do it once. Any help would be appreciated.
  2. wmodavis

    Well-Known Member

    Oct 23, 2010
    How much current does your project draw at 12VDC? If it is close to the maximum rating that the power supply will provide, the PS is operating near it's limit and it will tend to run warm or hot. Heat is the main factor that contributes to electronic failure. When reliability is a chief concern design so no component is operated at or near its maximum rating.

    Reliability costs. You will have to pay a bit more to choose any/all components with the next higher rating than what you could get by with. If all else is equal in the transformer such as quality of iron in the core, etc then a transformer rated at a higher current but used with the same project current should run cooler and therefore be more reliable. Even a cheap (RS) transformer used at say half its rated current will be more reliable. My guess is that a large portion of those who give a poor review to the transformer were pushing the limits and heat did its thing.

    Of course there are tradeoffs. Cost, size, weight.

    Look here http://signaltransformer.com/content/split-bobbin-with-isolation for one 'quality' option. I have used Signal brand transformers in commercial designs where cheap was not one of the spec's. I suggest you look at the 30VA size.

    Manufacturers technical libraries can provide lots of helpful information to help you make quality choices. Here is a link to Signal Transformer Technical Library. http://signaltransformer.com/content/technical-library.
    Last edited: Aug 1, 2011
  3. Go3Team

    Thread Starter New Member

    Aug 1, 2011
    Using 96 5mm IR LEDs, The calculator I used estimated it at 660mA. The next stage would be to multiply the LEDs by 1.5 and use 144. That would put the current draw at about 990mA. I would be looking to get at least twice that and up to 3 times that which would be about a 3A power supply.

    The transformers in the link you gave show 2.4VA, 6VA, and up. Would the VA rating also be the same as the amperage rating?

    What I'm trying to do is build a quality IR Illuminator for the same price or slightly more than a cheaply built Chinese import, so please forgive my "basic" questions, sometimes just googling the answer doesn't help you learn.

    Thanks again.
  4. SgtWookie


    Jul 17, 2007
    Here is a 5v, 4A regulated supply from MPJA for $5.95+shipping:

    You need to leave at least 1v or 10% of the voltage to drop across a current limiting resistor. Some LED "wizards" don't do that, and as a result you can fry your LEDs.