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 ...

There are many applications where the accuracy of a digital or analogue (bar graph) is not required but something better than a simple low/high indicator is desirable. A battery charge level indicator ...

Fig 1. This voltage regulator circuit (a) uses green LEDs as both the stabilization elements and as the voltage indicators at the front-panel switch (b). Fig 2. The addition of resistor R4 to the ...