2006-07-06 15:42:15 · 2 answers · asked by ? 1 in Computers & Internet ➔ Programming & Design
The typical way is to attach your source voltage to the anode of the LED (example +5v), then off the cathode of the LED, you have a current limit resistor (say 2.5k for 2 ma at 5v) then from the resistor to your logic gate. The logic gate goes low to turn on the LED, and high is off. Its called "sinking" and LED, where the opposite is called "sourcing" and LED.
Sorry, I just saw you asked WHY. Its always better to sink a LED then to source it, because you are just supplying a return path to ground instead of trying to drive it. Also if there is a failure in the LED circuit (a short) and you are driving it, you will burn up your logic gate.
2006-07-07 02:21:08 · answer #1 · answered by justme 7 · 0⤊ 0⤋
It's very cheap, no other parts required.
2006-07-06 23:01:40 · answer #2 · answered by Computer Guy 7 · 0⤊ 0⤋