Optical Buttons?

[Tiger-Heli]

The way the circuit is wired, it's backwards. So it would work properly if you held all buttons and let go of the one you want pressed.

Wouldn't this mean that it should work fine if you swapped the NC and NO wires?  (Sorry if I misunderstood).

[ShinAce]

Nope, you must respect the polarity of the photo-transistor as well as LED. I can't stress this enough. The proper way to make an optical switch is to buffer the signal and prevent hysterisis. The 74ls14 chip will do it for you. It has 14 pins: 2 for power, 6 for inputs, and 6 outputs. So you can buffer 6 buttons with one chip.

If you look about 8 posts back, you'll find the schematic I posted. And the method to reverse the logic is in that schematic as well. All that needs to be done is to swap the positions of the photo-transistor and it's resistor. So in the schematic, the photo-transistor is between the signal wire and gnd. Well, you put the resistor between those 2 wires instead.