3W Bridgelux LED wiring and PSU Help

Discussion in 'General Electronics Chat' started by PC Prudefish, Apr 7, 2014.

  1. PC Prudefish

    Thread Starter New Member

    Apr 5, 2014
    Hi guys, new to the forum after trying to find a simple answer to my puzzle and just getting more and more confused.
    I know some will think the answer is simple but I ask you to bear with me please and offer the simplest explanation with drawing if poss, so I cant fail. (I hope). I have used 12v supplies before to wire up3 and 5mm leds with resistors but these are completely different IIAC.
    Thanks in advance for any and all replies.:)

    I have the following that I could use (the drivers purchased after advice).

    10 Bridgelux 3w cool white Leds Voltage - min 3.5 - max 4.5v Current - 750mA
    6 Bridgelux 3w Royal Blue Leds Voltage - min 3.5 - max 4.5v Current - 750mA
    4 Bridgelux 3w Deep Red Leds Voltage - 2.6-2.8V Current - 800mA

    3 12v (constant v) 24w 2 amp dimmable psu eBayUK item No 390556572105
    3 12-24v low voltage dimmers eBay UK item No 151055417940
    Thought I might use these the old "add a resistor and go" way uh oh!

    Following advice I purchased 2 of these drivers, 230vac to 8-48v 1000mAh
    eBay UK item No 231012564360

    I want to make two tank lights, one for frags with 6 white 4 blue and two red
    and one for a Quarantine tank with 4 white 2 blue and 2 red.

    I did want to make the reds and blues dimmable but the power supplies arrived and are apparently not dimmable so is there anything I can do to make them dimmable.

    If any one can point me to my answer I will be extremely grateful.
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    First.. Lets assume series wiring..
    Then we need the max VF to determine the proper DC output rating of the power supply..

    Tank 1 = 6W + 4B + 2R
    (6*4.5)+(4*4.5)+(2*2.8) = 50.6V max
    (6*3.5)+(4*3.5)+(2*2.6) = 40.2V min

    Tank 2 = 4W + 2B + 2R
    (4*4.5)+(2*4.5)+(2*2.8) = 32.6V max
    (4*3.5)+(2*3.5)+(2*2.6) = 26.2V min

    What I would do is buy the following..
    1 x Meanwell LPF-40D-54 (this is for tank 1)
    1 x Meanwell LPF-25D-36 (this is for tank 2)
    2 x 100k potentiometers
    The datasheet for the power supplies is here
    See that the first power supply is rated 32.4 to 54VDC which is greater than the max and less than the min with a set output current at 100% dimming input of .76A or 760mA
    second datasheet here.

    First I hope you bought those LEDs on star boards..
    Assuming so you would.
    Mount LED's to heatsink using thermal adhesive between the bottom of the star board and heatsink..
    Solder wires to pads on circuit boards so that they are wired the LEDs in series.
    Attach to DC output of power supply..
    Wire the 100K pot across the dimming wires
    Put a plug on it to plug it into your outlet.

    Plug it in and voila.. dimmable LED fixture.. Turning the pots gives you brightness control..aka dimming.
  3. PC Prudefish

    Thread Starter New Member

    Apr 5, 2014
    Mcgyvr, you are a veritable genius. Thank you so much for pointing me in the right direction and explaining in the simplest terms what to do.
    You mention potentiometers, what value should I use please, and yes the LEDs were supplied on star boards.
    Thank you again.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    "100k ohm" potentiometer
  5. PC Prudefish

    Thread Starter New Member

    Apr 5, 2014
    Damn sorry ,you did mention it in your first post.
    Thank you again I will order from Mouser in the morning.
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    Check around.. onlinecomponents.com has better pricing for the drivers