NPN and PNP Checker




Introduction: NPN and PNP Checker

About: I am a student of BSCS but I'm interested in electronics that's why I would like to think about innovative ideas and try to build my ideas into reality and i also interested in making a robots. email id: degen…

Hello! friends

Welcome to my another rechargeable transistor tester. Today i'm gonna show you how to make your own transistor tester and how to fit into a earrings box just follow the steps.

So, let's get started.

Step 1: Circuit Diagram

With the help of this diagram we can build our own transistor tester project.

Step 2: Materials

You'll need

Resistors: 1k x 4 and one 2.2k

1n4007 diode

Female pin

Led's: red,yellow and green

3.7 volt battery

Veroboard (dotted)

Some npn and pnp transistors

Push button

8 pin base

Earrings small box

Mini drill

Hot glue

Step 3: Cutting

Take a piece of veroboard and cut it down according to the size of earrings box with the help of mini drill.

Step 4: Removing Sharp Edges

Remove the sharp edges and turned it into a round shape then it's look like this and easily fit into the box.

Step 5: Soldering Base

Take a base and soldering it carefully according to the diagram with the jumper wires.

Step 6: Making Circuit

Place the components on veroboard according to the diagram and soldering it and join the all connections of base with veroboard.

Step 7: Fitting

Make some holes according to your design and then take your all components and fit into the earrings box nicely. After all it's look like this.

Step 8: Plugging Chager

Plug your charger with you transistor tester project for charging. The red led is showing charger is plugged. Put the transistor taster in front of you and observe the left side of the 8 pin base in a column is NPN and the right side is for PNP. Same sequence for Left and right side of the base like this E,B,C,E (upward to downward) because some transistors have emitter,base,collecoter and some have emitter,collector and base. When you place a transistor at left side of the base which is NPN then green led is glow and when you put a trnasistor at right side of the base which is PNP then Yellow led is glow.

Now you are ready to use your transistor tester.

Step 9: Finish

It's rechargable and easy to pick and obeviously easy to use.

I hope you guys like it.

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    7 years ago

    great project

    can i place your project on my website.

    i'm working on a website which is related to electrical projects.

    i also mention your name.

    plz reply


    7 years ago

    Very useful gadget for electronics enthusiasts like me


    7 years ago

    I've made a better one in school as a kid. But yes a very handy project I think everyone needs one!

    Asadullah Mughal
    Asadullah Mughal

    Reply 7 years ago

    ScottieDigital yes its very useful with the help of this we can easily identify the npn and pnp transistors.


    7 years ago

    Good project ,

    A suggestion here . The only problem that I can see with your circuit is that if the transistor under test is internally " shorted " the led will light showing it to be good . You may want to put the " test " switch in the base circuit to turn the transistor on and off as a more dynamic test .Anyway ,

    Thanks for the project ! I built a
    transistor tester a long time ago using a simple oscillator circuit .
    Using PNP and NPN transistors , with sockets . I could substitute the
    transistor in question into the socket . Here is basically the circuit :

    If it oscillates , then the transistor is working . Basically a dynamic test .

    Cheers , take care , and have a good day !!...