My question is: Can I connect GND to 6v so the voltage difference of the led is 6v??? (12v-6v=6v)
question is...how much current to power the led is required?that circuit is overkill... and yes the same circuit would be fine, r2 is doing the work to protect the diode.
Where's the 6V coming from? If you have a 6V supply, why don't you use it directly instead of trying to subtract?
Why so convoluted?Just drive with 3 logic level, low Rds, low Gate capacitance, N-channel MOSFETshttp://www.digikey.com/product-detail/en/NTD5867NL-1G/NTD5867NL-1GOS-ND/240142210k pulldown resistor to hold gate off while arduino starts up.
I think this is the way to go, as someone in another forum told me:
Ok, the led is this one: http://www.alibaba.com/product-gs/712130845/10_Watt_RGB_LED_high_power.html
That will work better using a voltage regulator for the Red.Can you snip off the top of the device so you have seperate anodes for the 3 LEDs?Then you can have 12V for Green & Blue, and regulated 8V for the Red, and the cathodes can connect to your circuit above.
I would switch to a forum where they didn't tell you such rubbish.For a start that is not a proper circuit and second you always need one resistor per LED.
The circuit is PWM controlled linear constant current sink supply, at 12V LED case it achieve >90% efficiency and without EMI. You might upgrade BUZ71 to logic type MOSFET to make it more Arduino friendly.Now for 6V LED, all you need to do is upgrading heat sink of Q1, efficiency will drop to ~50%. That's all.
"Ohm's Law" for an inductorv=L*(di/dt)