EMF(Electromagnetic Field) Detector




About: Electromechanical Engineer, Product Designer, Maker. I love to make prototypes and teach others in the process. I graduated from UCF and spent two years working at NASA.

Intro: EMF(Electromagnetic Field) Detector

This is a quick and easy instructable on how to make your own EMF Detector. You can use it to detect electromagnetic fields produced by your electronics. I like how the addition of the piezo buzzer makes it sound like a geiger counter for detecting radiation.

Step 1: Things You Will Need

1. Arduino or other suitable microcontroller.

2. Antenna like this one.

3. 3 Mega Ohm resistor.

4. LED (You can use the on board LED if you would like)

5. Small Piezo Buzzer

6. Battery. I like cylindrical batteries like these but you can use a 9V Battery.

7. Wire

8. Soldering Iron and Solder

9. Screw for attaching antenna.

Step 2: Wire It Up

Simply connect the Piezo Buzzer and LED in parallel between ground and digital pin 11. It doesn't have to be pin 11, just a pin with pwm(pulse width modulation) capabilities. On most Arduino boards, pwm works on digital pins 3, 5, 6, 9, 10, and 11.

Wire a 3 Mega Ohm resistor between ground and analog pin 5 and your antenna to analog pin 5.

If you have an Arduino with solderable contacts for the pins, it is much easier to wire up.

Step 3: Upload the Code

Just upload the code to your Arduino and you're ready to go. This code is from another project found here. He just used a piece of wire and an LED. His project inspired me to make this instructable.

Thank you.



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    13 Discussions

    Varen Greycloak

    2 years ago

    I've tried to expand upon this design but I've hit a fairly big roadblock... Somewhere.


    3 years ago

    Cool and fun project, congratulations.
    What happens if I increase or decrease the resistance? Will it change the sensibility to EMF? Thanks.


    3 years ago

    This is nice! Could you display the code in a way that I could copy and paste it?

    Varen Greycloak

    3 years ago

    Do you know the specs on your buzzer? I'd like a Geiger counter sound like yours, not a screaming circuit board.

    3 replies

    Unfortunately, I do not. I have a drawer full of buzzers that I pulled out of other things but you can get this effect with pretty much any continuous tone buzzer. The code is generating the effect, not the buzzer. PWM on the buzzer pin gives that flickering geiger counter sound. The PWM is being mapped to how strong of an EMF that it is picking up.

    Varen GreycloakProto G

    Reply 3 years ago

    Alright. The only thing I can't seem to find is the specific resistor.


    3 years ago on Introduction

    Do you think that the EMF detector can be used to detect Lightning, if placed outside?

    I am definitely going to put one of these in a 'Geiger counter style box' and then place a small electromagnet in one of my friends backpacks. I then brandish out the 'Geiger counter' and watch my freinds horror when I go up to his backpack :)

    1 reply