I ripped out a pcb from an old midi controller, and on it is a 3 digit 7 segment display, a four pin button with an LED in it (seems controlled by the two middle pins), and a four pin fader (with two pins on ground, so presumably this is just a potentiometer?). All powered by a breakout cable.
Ok, I've figured out how to control the 7 segment display just fine, BUT, Pin 12, when HIGH, selects the third digit AND it also turns on the LED in the button.
If I wanted to control this LED in the button, would I have to control the negative side of it instead? Right now it just goes to ground, but I think I could just put a transitor inbetween it and the ground rail on my breadboard, then control the transitor for when I want that button LED to turn on.
Yes, control one side of the LED via other means makes sense.
If running from 5v, maybe just ensure there is a current limit resistor and control from an arduino pin directly.
CrossRoads:
Yes, control one side of the LED via other means makes sense.
If running from 5v, maybe just ensure there is a current limit resistor and control from an arduino pin directly.
Cool, I'm glad to know I'm getting the hang of this (at least conceptually).
There is a resistor on the positive side already (though, this makes the 3rd digit kind of dark since all those LEDs AND the LED on the button use the same current, but whatever). So you're suggesting that the negative side of that LED goes directly into a pin on the arduino? Do I control this as an output pin and simply toggle between LOW/HIGH when I want the LED in the button on or off?