While LEDs are common in voltage detection applications, I have never seen an LED circuit that is dedicated to indicating the presence of low values of current flow. This simple LED current sensor ...

I needed a simple LED indicator showing that a particular voltage level had been reached—specifically, that a capacitor had charged to a particular potential. I was convinced that there must be a way ...

This LED DC voltage indicator circuit is a voltmeter, rather than simply a battery tester. As such it may measure voltages as low as 3V. It utilizes venerable LM741 operational amplifiers applied as ...