LED Constant current array help

Discussion in 'The Projects Forum' started by orchiid.wild, Sep 14, 2011.

  1. orchiid.wild

    Thread Starter New Member

    Sep 14, 2011
    7
    0
    Hey!

    I know nearly nothing about electronics but I'm on a mission to build an LED array.

    Here's my a list of my equipment and following that will be an explanation of how I plan to assemble it.

    _____________________________________________________________
    PARTS:
    1x 670mA 36W Power Constant Current Source LED Driver (input: 85~265V output: DC 28-45V)
    http://www.dealextreme.com/p/waterp...stant-current-source-led-driver-85-265v-42906

    2x 9Vf Warm White LUXEON Tristar LED
    http://www.luxeonstar.com/Warm-White-3100K-20mm-Tri-Star-Rebel-330-lm-p/mr-ww060-20t.htm

    1x 6.3Vf Red LUXEON Tristar LED
    http://www.luxeonstar.com/Red-627-nm-20mm-Tri-Star-Rebel-306-lm-p/mr-d2050-20t.htm

    1x 6.6Vf Deep Red LUXEON Tristar LED
    http://www.luxeonstar.com/Deep-Red-655-nm-20mm-Tri-Star-Rebel-LED-p/mr-d3350-20t.htm

    1x 9.3Vf Blue LUXEON Tristar LED
    http://www.luxeonstar.com/Blue-470nm-20mm-Tri-Star-Rebel-174-lm-p/mr-b0030-20t.htm
    ______________________________________________________________

    Power supply will be wired the plugged into the wall. Power supplies output will be connected to all LEDs in series for a total of 40.2Vf (well under the 45V max).

    How do these power supplies work?
    I understand the current is CONSTANT as the name implies. If the voltage variable depending what kind of load you put on the circuit?

    I'll also heat sink everything and strap a fan on to keep things cool.

    Will this work?
    Is my thinking right?
     
  2. vrainom

    Member

    Sep 8, 2011
    109
    19
    I'm pretty sure it will =)

    Yes the current is constant and the voltage is variable because the led's voltage drop isn't constant.
     
  3. Ratneswar Tulsiary

    New Member

    Sep 13, 2011
    1
    0
    well done.hope you can do better
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    You only need one or the other regulator, not both.

    I would use something similar to this...

    [​IMG]

    It has a reasonably low parts count. However, it will get very hot, depending. You will need adaquate heatsinking, and possibly a fan. This is just an illustration, you would need to modify this design to your needs.

    A SMPS constant current source will run much, much cooler and be a lot more efficiently (the two are related). Google buck puck. We have several untested experimental designs you could try out.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,030
    It looks OK to me: The LEDs can tolerate a bit more current than that supply produces, the total Vf is OK as you've noted. All is good.

    The price of that supply is tough to beat unless you've got parts already in hand and enjoy the DIY approach.

    The thing I'd think about before turning it on is heat dissipation. Make sure those LEDs are kept cool at that current level. The current spec for the LED is probably for some ideal world that is really tough to achieve, and your supply is getting close to that spec. So better give it some thought.
     
  6. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Before you turn them on....Heat sink, heat sink, heat sink.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Let me add a couple more to drive the point home.. Heat sink, heat sink, heat sink, heat sink, heat, sink...and fan (air movement makes all the difference in the world)
     
  8. orchiid.wild

    Thread Starter New Member

    Sep 14, 2011
    7
    0
    You guys are UNBELIEVABLE!
    I'm going to post a new thread on this but does anyone have thoughts on where to buy LEDs with specific wavelengths?

    I've been searching around online and there's various sources but I feel that the Luxeon website is the best option. I've read their LEDs are good, and the website seems to imply that the REBEL series are the most up to date versions of their LEDs.

    DealExtreme.com has LEDs for cheaper but I have no idea what the wavelengths are and I have no IDEA in the world how to figure out which LED they're selling exactly based on the BIN/item code they may/may not have provided and then matching that code to the naming guide baffles me.

    I've looked through MOUSER.com and NEWARK.com but I don't want to end up buying LEDs that are old models and less efficient.

    THANKS again you guys are all over this stuff.

    PS. Bill, I can read a basic circuit diagram but the one you provided confuses me. If everyone else is saying what I have planned will work I think I'll just go with that. BUT I'm always keen to learn and improve on my design.

    ;)
     
  9. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Luxeon LED are definitely good and have an abundance of documentation.
    Cree is another good brand. http://www.cree.com/
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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  11. orchiid.wild

    Thread Starter New Member

    Sep 14, 2011
    7
    0
    Yea I've heard CREE is good but I have no idea how to figure out which LEDs are which and when I buy them I need to know exactly what wavelength each diode is emitting. Luxeon's website is far more straight forward.
     
  12. orchiid.wild

    Thread Starter New Member

    Sep 14, 2011
    7
    0
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