Each of the following diagrams illustrates how the same basic circuit can be used to create an LED-lit accessory that can be switched on an off. These circuits are similar to the practice LED circuit ...

I have used Red and Green LED’s. When node A is positive green LED glows while when node B is positive, Red LED glows. This indicates polarity of the input d.c voltage . 2) LED as a Continuity tester: ...

High-brightness LEDs, with independent delay and duration, find use in a visual-inspection application. This circuit is not complex, but it saved the day in an application involving visual inspection ...