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: ...

Simple Threshold Switch For An LED Indicator Oct. 9, 2008 I needed a simple LED indicator showing that a particular voltage level had been reached—specifically, that a capacitor had charged to a ...

For this application, the LED proved to be a decent reference diode. It has a temperature coefficient that tracks fairly well with that of Q1, and the LED reaches its turn-on knee with less current ...

For under $20 you can get a LED tester (look for TV back light tester) that’ll test anything from IR LEDs @ 1.2v up to 300v. Not sure why so high when TV back lights are usually around 100v.

[PatH] from WhiskeyTangoHotel choose the latter route, and built a super simple LED controller for his KLR650 bike. He chose a commonly available 18 W light bar module containing six 3 W LEDs.