The most commonly used component in electronics is a Transistor and it keeps failing. You have to check the working of the transistor through the multimeter. By testing one terminal after another which can be time-consuming. These multimeters and transistor testers are complex to understand and design. But in this tutorial, we are going to make a simple Transistor Tester Circuit which can test both PNP and NPN transistors.
This circuit is easy to make and very convenient for testing transistors. It indicates the working of the transistors through two different LEDs. One for NPN transistor and the other for PNP transistor.
Hardware Components
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Stepdown Transformer | 230V/6V AC | 1 |
| 2. | Switch | Rotary | 1 |
| 3. | Resistor | 2.2KΩ, 22KΩ, 68KΩ, 270KΩ, 2.2MΩ, 680Ω | 1, 1, 1, 1, 1, 2 |
| 4. | Diode | 1N4001 | 2 |
| 5. | LED | RED, GREEN | 1, 1 |
Circuit Diagram
Circuit Connections
As you know there are three terminals of a transistor, Base, Emitter, and Collector. To connect a transistor with this circuit we have marked three points in the circuit diagram as you can see. It is important to put the transistor leads in the right direction. Transistor emitter with circuit emitter where (E) is marked. transistor base with circuit base where (B) is marked and transistor collector with circuit collector marked as C. If you don’t connect them with their respective points this circuit will not give accurate results.
Working Explanation
The 230V AC coming from the mains power supply is stepped down to the required voltage of operation (6 volts) through a transformer. Different resistors are used in this circuit to be used as a current limiter for transistors being checked. A rotary switch S1 is used to choose a correct base resistor for the transistor. We are using two LEDs in this circuit. Green LED for NPN transistors and Red LED for PNP transistors.
A resistor is connected with each LED to limit the base current. Green LED will light up when the NPN transistor is working properly and the Red LED will glow when the PNP transistor is working correctly.
