This project is a transistor analyzer, suitable for testing both NPN and PNP transistors. Its circuit is simple as compared to other transistor testers which is useful for both technicians and students. It can be easily accumulated on a general purpose PCB. Basic electronic components like resistors, LED’s, diode and NE5555 are used for developing this circuit. Using this transistor tester circuit, many of the faults can be checked like transistor is in good condition or not, is it opened or shorted, and so on.
NE555: As the name suggests, NE 555 is multivibrator IC which is popularly known to work in three modes: astable, monostable and bistable. Also, circuit can work through a battery for a longer duration, without compromising the working abilities or disturbing the normal functioning of the passive components attached.
The 555 timer project operates at 2 Hz of frequency. The output pins 3 drives the transistor tester circuit with positive voltage and then zero voltage. The other end a voltage divider is connected with the mid-point at approx 4.5V. When no transistor is connected to the tester the red and green colour LEDs flash alternatively.
Test Result
1. When transistor is put on the test lead both the LEDs blinks.
2. The transistor will be in OK condition when only 1 LED flashes. As it will produce short across the LED pair when the voltage is only in one direction.
3. The transistor will be open if both the LED flashes after connecting the transistor.
4. The transistor will be shorted if none of the LED flashes.
Circuit Diagrams
Project Components
Filed Under: 555 Timers, Electronic Projects
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