in my case i use LM317 , Q1 = bc337 , r1 = 2 k , r2 = 2,2 k , pot = 4.7 k , C = 47 uF , r3 = 0.8 r
use this circuit for my luxeon LXHL-LW3C - drive with 3.75 V / 1000 mA = supply circuit just ac/dc adapter ( 7,5 V / 1000 mA ) work well with 6,5 V up to 12 V ( for this moment i don`t test with more voltage )
i give info :
R3 is the "sense resistor" for the current-limiting circuit. select the value of R3 as follows: R3 = 0.55 / (LED string current). so for my circuit I have R3 = 0.55 / 0.8 = 0.69 ohms. resistors don't come in every possible value, the closest match was 0.68 ohms. you also need a resistor that can handle a bit of power, use this guideline:
Selecting R4 control slider/dial
First choose if you want a slider or dial! this is your user interface for your controls. It's less work to make a control panel using dials, because you just drill a hole for them, but you might prefer the look & feel of the sliders. I went with the sliders, but you'll see how much of a hassle they were later. any dial or slider between 2k-ohm and 10k-ohm will work. a 2k-ohm is the best because it allows precise calculation of the output voltage without testing. for sliders, i was only able to find 10k-ohm sliders which required a bit of trial-and-error to get the output voltages correct.
Setting R1 and R2 control range resistors
The combination of R1, R2 and R4 set the output voltage (= LED brightness) of the regulator. the output voltage is approximately equal to: 1.25 * (1 + ((R2+R4) / R1)). This becomes less accurate with larger R values. With a 2.5k dial for R4, the formula will be very close, with a 10k dial, you'll need to hand-test your R1, R2 values. below i work through two examples: one with 10k slider and one with 2.5k dial.
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