I'm using a Mega R3 with seven, backlit, lcds. Each LCD has three LEDs drawing 20mA. Since this would exceed the limits of the arduino, I am planning on using a separate power supply for the LEDs and the contrast pins (Vo on the lcds.)
The problem I'm concerned about is that each display has a common ground for all of its circuitry, so the display will need to be grounded to arduino and to the other power supply through only one pin.
Is this actually a problem? Is solving it as simple as tying the grounds together?