I'm putting together a project where I'll be driving 4 x 10W RGB LEDs (these ones) with one PicoBuck LED driver. I'll be using all three channels on the LEDs at the same time and controlling dimming with an Arduino Uno using PWM. I'll be using heatsinks on each LED.
What power supply should I be looking at using for the LED driver and therefore the LEDs? I'll be honest that I'm a bit confused about the voltage requirements of LEDs - is it enough to use a DC power supply that supplies in this case at least around 40W and at least 350 mA current, regardless of its voltage? For example could I use a 19.5V 65W laptop DC power supply, of which I have several to hand? (for reference, I derived 40W from the maximum forward voltage of the three RGB channels added together (7 + 11 + 11 = 29) multiplied by the number of LED chips (4) multiplied by DC forward current of each channel (350mA) = 29 x 4 x 0.350 = 40.6)
Do you think I can achieve this project with just one of these PicoBuck LED drivers, if the four LED chips are connected in series (diagram attached)? The PicoBuck uses the Al8805 chip, a high efficiency 36V 1A buck LED driver. It says that "the device can drive up to 8 LEDs, depending on the forward voltage of the LEDs, in series from a voltage source of 6V to 36V.". Does this mean that if I am using 4 RGB LEDS, this is considered as 4 LEDS, or would it be 12 LEDS, considering each LED has 3 channels with separate power? If the latter, there is the possibility of dropping the number of LEDs to 3 for this project.
I was looking at using a heatsink for each LED with a thermal resistance of 5.8°C/W - would this be suitable?
- Forward voltage at 350mA:
- red 6.0 min 7.0V max,
- green and blue 9.0 min 11.0V max
DC forward current: 350mA each channel
EDIT: the setup will be outside in winter, so we're looking at average maximum 9.0 °C | 50 °F and minimum - 1.0 °C | 30.0°F (at least round these parts)