I figured out how to successfully drive a large LED bank with external power by the same circuit that powers the "C" LED on the APM 1.4 shield. I am thinking of putting together a how-to Blog post with the circuit, but I'm just wondering if there is any interest first?
Basically just using a simple MOSFET triggered off a pin on the IMU shield, you can drive a virtually unlimited load while drawing "virtually zero" amps on the APM board.
The idea behind it was that I can't see the LED's when the APM is in my heli. I wanted external LED's to signal armed/disarmed. I'm going to be using the same LED's for navigation lights.
I figure you quad guys might be interested too?