12VAC and 12VDC fixtures on same 12VAC transformer?

Discussion in 'The Projects Forum' started by jamesr219, Dec 20, 2012.

  1. jamesr219

    Thread Starter New Member

    Dec 20, 2012
    2
    0
    Hello,

    I have a wall unit where I would like to put a single 12VAC light in the middle (only LED gimbal I could find) and then have LED tape lights along the shelves, but those are 12VDC.

    I am using Juno MG1L3K-FL-BZ light in the center and this is 5W, 12VAC. I was planning on using a 12VAC transformer to power this but I would also like to use the same transformer to power about 48linear feet of LED tape lighting. Something like this:
    http://www.superbrightleds.com/more...ries-High-Power-LED-Flexible-Light-Strip/998/

    These are about 90mA/foot. There are 8x6' sections which need to be powered.

    I plan on using an electronic transformer and an ELV dimmer to make everything dimable. It is my understanding the electronic transformer basically makes the output like 20kHz @ 12VAC.

    so, my questions:

    1) Is this possible with simple rectifier and filter?
    2) Any IC chips or power supply chips which might make it easier? The LED tape lights can run from 9VDC-14.8VDC.
    3) How do I need to properly size the 12VAC transformer?

    Any other suggestions on how I can get this to work?

    Thanks!

    -jr
     
  2. BReeves

    Member

    Nov 24, 2012
    412
    64
    Use a 110-12 volt transformer. Just make sure the transformer is rated for the current you are going to draw and stick in a diode for the DC, no real need to filter the DC for the lights.

    Neber mind, forgot you wanted a dimmer..
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    A LED will only light when presented with a direct current. I've seen a more then a few low voltage LED lamps that are intended to run off 12 VAC or in low voltage AC systems.

    These all have in common is a bridge rectifier to convert the AC to DC.

    Thus I would expect your AC LED bulb to work just fine off DC.

    Now the DC strip lights are a different matter. These don't seem to have that bridge rectifier inside,and LEDs make lousy reverse blocking diodes, so they may well fail if given AC power directly. However, if a bridge rectifier is added, these should then work just fine off AC power.

    As far as dimming goes... it depends. In many of the LEDs I've opened up some have resistors (which should be dim-able) and some have constant current sources (which are not dim-able).
     
  4. jamesr219

    Thread Starter New Member

    Dec 20, 2012
    2
    0
    I can test this? Any suggestions on how to safely do it? Just a 12VDC power supply and a resistor (to limit current) or is the resistor likely not even needed?

    Any suggestions on chips I can use? I've seen potted devices meant for this type of thing with screw hole in middle? Would something like this be enough? I'm assuming the ripple really isn't all that important to smooth out?

    The LEDs I am talking about using are specifically mentioned as dimable, so I am thinking that it is simply a resistor.. The link is here: http://www.superbrightleds.com/more...ries-High-Power-LED-Flexible-Light-Strip/998/

    -jr
     
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