Stupid question about powering LED lighting system

Discussion in 'The Projects Forum' started by src, Aug 18, 2008.

  1. src

    Thread Starter New Member

    Aug 18, 2008
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    I've got a Phillips Aurelle LED lighting system (actually, 6 of them) that I would like to tie to the same power source. Each kit comes with a transformer that can power up to 2 of the kits. I would like to find a transformer that can handle the whole lot. Unfortunately, my electronics education stopped at High School, and that was some time ago.

    The only specs I can find on the lights are 12VDC forward voltage, 20mA forward current. The transformers are 9VDC, 500 mA with a 4.5W maximum load. This is for an outdoor application, although I could probably mount the transformer indoors if I had to.

    The only low-voltage outdoor lighting transformers I can find are 12V units. I'm not sure, but I expect that using one of those would damage the lights. Are there any recommendations you can give me on what to use, or at least what I can/cannot use to power this system? I know I can find a 9v indoor transformer of at least 2 amps (wall-wart style), but would rather solve the problem correctly if possible.

    Thanks in advance for any help!
     
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    OK, if the supplied transformers are rated at 9V, 500mA, and it can power up to two of the kits, the lights must say something other than 12v 20mA - either that, or the manufacturer is relying on the fact that the lightly-loaded 9v unregulated power supply will measure much higher when it is lightly loaded.

    Can you re-read the specs to make sure?
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    Buy a 240VAC to 12VDC universal regulator adaptor rated at 500mA and you will be fine.

    Are you sure that the leds are 12VDC?

    Are they coming with a ressitor? if yes, what is its value?
     
  5. src

    Thread Starter New Member

    Aug 18, 2008
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    Thanks for the responses. There are 10 LED lamps in each kit, so 1 of the original power supplies can handle 20 lights. I don't know if there are any resistors, since the lamps are in sealed enclosures. These kits are for deck lighting.

    I've gone back over the spec sheets, but I still can't find any better info that I put in my first post. I have to assume that the light specs are for an individual lamp, not the full cluster of 10. Sorry for leaving out the details on the number of lights in a kit.
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    If the enclosure of the lamps specifies a voltage of 12 volts DC then buy a universal regulator wall adaptor. Tell us how many kids you want to power with this adaptor as to tell you the current rating of it.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    OK, that was the missing piece to the puzzle. Yes, the spec was for a single light; current in parallel is additive.
    Each lamp requires 20mA current; there are 10 lamps per kit for 200mA total current.

    So, you actually require 9v @ 1200mA (1.2A) to power all six kits from a single supply.

    A regulated supply would be a good idea, as that would ensure that your lights would have a long and happy life. You'd probably have to have such a supply indoors though. If you want the supply to be outdoors, you'll have to find one that is rated for constant service outdoors, or have a suitable enclosure for it installed.
     
  8. src

    Thread Starter New Member

    Aug 18, 2008
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    OK, thanks. I was a bit thrown by the 12 volt forward voltage spec on the lights. It made me wonder if I can use a 12v supply instead of 9v. I'm having no luck finding an outdoor 9v transformer, while 12v transformers are pretty easy to come by.

    But, as you say, in the worst case I'll just put it indoors. I appreciate all the help!
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Well, try measuring the actual voltage output from your 9v supplies with no load on them; and then compare when you have one string of 10 lamps connected. It may very well be that they are not regulated, and under such conditions output a significantly higher voltage.

    I don't know; I don't have them here in front of me. It's up to you to do some detective work with a good meter.
     
  10. twaroc

    Member

    Sep 20, 2007
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    Can you find any 18V outdoor regulators? You could always put two of your LED strings in series. That's a pretty good ghetto rig though - and your brightness from strand to strand might be a little off.
     
  11. src

    Thread Starter New Member

    Aug 18, 2008
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    Thanks for bringing that up - it prevented an error on my part during installation. I hadn't even considered the series/parallel issue - like I said, it's been a LONG time since I had to do much thought about electrical circuits. While I haven't forgotten the difference between series and parallel circuits, I had forgotten to plan for it.
     
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