It may also be used to check a string of LEDs (one at a time) to make sure that all are installed correctly. LED Tester Circuit Schematic simple led tester schematic. Why 3V? 3V is sufficient to turn ...

3V LED earrings using ATtiny85 ... Following is the circuit diagram of the earring. ... Though this is a simple project, be careful with the polarity of the LEDs when sldering them to the rest of the ...

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 ...