9 responses to “Dimming power leds with Arduino”

  1. Robin

    Very interesting! Useful circuit diagram. I’m about to do something similar. Are the LEDs run cooler at dimmer light levels? Thanks!

  2. razor

    Do you have scheme of dimmer adjust by timer?
    (for aquarium lighting with day and nigh simulation)

  3. Abizar

    Why not put a variable resistor after or before your R1? The constant current from an LM317 in the configuration you have is I=1.25/R (so, 1 ohm will give you 1.25A; 10 ohm will be 125mA). You then don’t need the transistor and of course the beloved Arduino. A 1 k variable multiturn in series with the 1.8 ohm will give you nice control from about 1 mA to 700 mA.

  4. Abizar

    Assuming you use a 1.8 ohm and a 1 k pot in series, then the maximum wattage would be 0.9W for a 700mA current. As you increase the resistance in your pot the wattage would decrease, at 10 ohms on the pot, watts would be 0.13W, at 100 ohms, 0.02W. Most wirewounds (about 1 in dia bodies, the blue ones from bourns) are about 5 W. 1″ dia. cermets are 3 W.

  5. robotic

    Can you tell me effect of R2? Thank you very much^^

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