Is this actually a problem? Is solving it as simple as tying the grounds together?
The current will be consumed by the LEDs, not routed back through ground.
QuoteThe current will be consumed by the LEDs, not routed back through ground.The way to guarantee this is to be sure the - pin ["ground"] of the separate power supply is connectedto the LCD grounds and not to the Arduino board ground.
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?