So I'm designing a project that will have about 75 LEDs and will be controlled by multiple Arduinos. I want to have a lamp test push button so I can light all the lights at once and see any that are broken. So I've been looking around and what little on lamp test I been able to find is to use a diode between the LED and lamp test buss so that power doesn't feed back into the lamp test buss and go places it shouldn't. The question is should I put a similar diode between the Arduino output pin and the LED, so that lamp test buss power doesn't feed back into it? The lamp test buss will be +5V just like the Arduino output. It will be a separate power supply that can deliver enough current to run all the LEDs at once without getting unhappy.
Anyone with lamp test experience that can enlighten me?