I'm using three PWM outputs from an Arduino Mini Pro to drive the R/G/B parts of some strips of LEDs. The circuit is basically this:
I've got a single 12V power supply, rated at 200W, to light the LEDs and to power the Arduino via the RAW pin, and there are 5 metres of 60LEDs/m RGB LEDs, i.e. a total of 300 LEDs, which should be drawing ~72W according to the spec sheet (14.4W/m).
The problem is that even when the sketch says
digitalWrite(9, 255); digitalWrite(10, 255); digitalWrite(11,255), the LEDs are considerably dimmer than when connected directly to the 12V supply. My cheap, digital volt meter measures ~8.1V
between GND and the PWM pins across the LEDs, not the 12V that the transformer is supplying.
Am I doing something wrong? Does the MOSFET really cause such a large drop in voltage? Is there anything I can do to mitigate it? (It's important to get as much brightness as possible from the LEDs for this project).