# How to Make Your Own Emf Detector || BJT As a Switch

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## Introduction: How to Make Your Own Emf Detector || BJT As a Switch

We can sense voltage in a circuit using a multimeter by connecting two probes at two different point in a circuit ie basically contact voltage detector.

As far as the era is concerned there also exist Non contact voltage detector. You can simply buy one,but that will be too boring for an electronics enthusiast.

## Step 1: Link for the Video.

Go check out the tutorial for more clear instructions and the build.

## Step 2: Parts List.

The parts list for this project is very simple any easily available.

Amazon.com

1.BC547-https://goo.gl/Z5hHPH

2.1M ohm resistor-https://goo.gl/vc0DFA

3.100K ohm resistor-https://goo.gl/vc0DFA

4.39K ohm resistor- https://goo.gl/vc0DFA

5.5mm Red led-https://goo.gl/s0Xzai

6.9V battery and battery connector

## Step 3: Connections and Circuit Diagram

The circuit for emf detector has 4 transistor connected in cascade form. Connecting transistor in cascade form helps the gain to increase.The overall gain is the product of individual gain of each transistor which inturn lights the led.

Its always a good idea to build a circuit on a breadboard.

## Step 4: Fitting in a Enclosure

Time to pack everything in a enclosure,Drill two holes,one for the led and the other for the Momentary switch.

Solider the momentary switch to the board,connect the battey…..and the project is complete.

Thanks for watching.

Stay connected for more videos and I'll see you next week.

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## 6 Discussions

what are you connecting the switch and led to?i mean which terminal of the pcb and also the other part which is being connected at the top?

You'd better replace the pot with a fixed resistor, if one set it to 0 the Led wil burn !

what resistor will be suitable for the circuit?

Yes,you are absolutely right.
I used it to adjust the brightness of the led,if you follow my case you just have to be a bit careful.

Thanks mate :)