The resistor in series with the LED string provides a convenient point to measure LED current via its voltage drop. Figure 2 The chopper operation is similar to the circuit of Figure 1; the larger LED ...

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 ...

The physical mechanisms worked the same as with any LED: when excited by the applied voltage, electrons and holes have a certain probability of generating photons. The researchers didn’t try to ...