Using a few diodes and a LED, you can make a nice indicator as shown in associated schematic diagram that can be used for a lot of applications (with a bit of luck). It’s quite suitable for use in ...

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 ...

If you’re working with 3.3V or 5V circuits, it’s easy for you to throw on a power or status LED here or there. [Tom Gralewicz] has found himself in a pickle, though, often working on projects with ...

There are a few caveats, though.