I have implemented a PWM controlled LED backlight for the LCD in my Arduino Uno design. One LCD backlight pin is connected to +5V, the second to the ground via 220 Ohm resistor and MOSFET controlled from a PWM capable D9 pin.
Everything seems to work fine, I do not see any oscillation, but after some reading about PWM I am not sure if I perhaps should connect a 100 uF capacitor to smooth the voltage?
Is the MOSFET even necessary? It seems backlight is drawing about 5 mA - can I perhaps drive it directly from the D9 pin, using the resistor? (It seems another user in Do I need to use a resistor if I am using a potentiometer to control an LED's brightness? is controlling brightness without any of those.)