LXHL-LW3C drive circuit

Discussion in 'The Projects Forum' started by smilem, Jan 15, 2009.

  1. smilem

    Thread Starter Active Member

    Jul 23, 2008
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  2. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Here are specs:

    Luxeon III Star LED - White Lambertian, 65 lm @ 700mA

    LXHL-LW3C Specifications:
    Lumens @ 700mA: 65 lm
    Max Continuous Current: 1000 mA
    Forward Voltage : 3.9 Vf
    Dominant Wavelength: 5500 K
    LED Type: Star
    Radiation Pattern: Lambertian
    Weight: 5.5g

    I see commercial power supplies are rated for 700mA of power for 3W LED like I have and 350mA for 1W LED.

    ----------------------------------------------------
    My power supply: 12V Here is how I calculated the resistor for LM317T 1.5Amps IC:

    (12v-3.9v)/0.700mA=11.571/0.700=16.53Ohms

    Are my calculations correct??? because this calculator here:
    http://www.reuk.co.uk/LM317-Current-Calculator.htm

    Shows me that I need 1.8Ohms 0.88W resistor
     
    Last edited: Jan 18, 2009
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Your calculations are wrong.

    The website's calculations are based upon a typical Vref of 1.25v. Yours may be as low as 1.2, or as high as 1.3. You will need to measure it to make certain, by connecting a 100 Ohm resistor between the OUT and ADJ terminals, and connect 3v to 30v between the IN and ADJ terminals. Measure Vref between then OUT and ADJ terminals using an accurate DMM (digital multimeter).

    You will need a heatsink for both the LED, and for the LM317T.
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Some have found simple ways to build regulators. See the website
    Instructables. I can not vouch for their accuracy or quality.
     
  6. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Thanks, I now changed my LED to 1W 350mA version, it suppose to give me 90% CRI rating versus 70% for "cold white" versions.

    I'll measure my Vref of voltage and post it.

    BTW anyone knows how to know Luxeon LED model? My LED has no writings etc.
     
  7. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Do you have a closeup pic of both sides?
    Maybe it's a fraud!
     
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