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 ...

An LED is commonly used as a "power on" indicator for many electronic devices. For the LED to produce discernible visible light in daylight, the forward-bias current needs to be in the moderate range ...

You’ve got an apparently simple design requirement on your latest AC-line powered project: provide a distinctly illuminated indicator to show that the unit is plugged into the line and that power is ...