LED detector

This tester can detect the polarity of light-emitting diodes to determine their luminous performance. In batch testing, compared with testing methods such as multimeters, it saves time, effort, and is simple and intuitive. The circuit is as shown in the figure below. One operational amplifier is connected to a low-frequency self-excited oscillator, which intermittently outputs high level or low level at the output end. The other op amp is connected in the form of an inverter. When the oscillation circuit outputs a high level, the inverter outputs a low level; when the oscillation circuit outputs a low level, the inverter outputs a high level. If a light-emitting diode is connected across the two output ends, regardless of the polarity of the jumper, the light-emitting diode will always turn on and emit light intermittently according to the oscillation frequency of the oscillation circuit. LED is a power indicator tube and also serves as a comparison tube for luminous intensity. The op amp IC can be LM358 or LM324.