Arduino EMF (Electromagnetic Field) Detector




A while back I saw an EMF (Electromagnetic Field) Detector at that used a led bargraph. I decided to modify it to use a 7-Segment LED Display! Here's my project. Sorry I don't have any pictures of it in use. Hopefully I can post some soon. 

Credit goes to Aaron ALAI for the original project. Also Conner Cunningham at Make: for doing a remake.

Have fun, work hard, & play nice! If you have questions please ask them!

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Step 1: The Stuff:

The parts & tools.

- Arduino
- 7-Segment LED Display
- 3.3M Resistor (Orange, Orange, Green)
- 470 ohm resistor (Yellow, Violet, Brown) or a similar value for the LED display
- Wire. I'm using 26 gauge wire
- Breadboard

- Computer with Arduino IDE
- USB A-B cable for Arduino
- Wire Strippers

Step 2: Wire the 7-Segment LED Display

This is probably one of the most confusing parts of the project, so I'll try to be clear. But if I'm not please ask any questions you have.
I used pins 2-8 on my arduino for the display. I wired the pins on the display counter-clockwise starting at the upper-left corner. Hopefully the pictures help explain it better.

Picture 1) Display before installation.
Picture 2) Display after installation.
Picture 3) Pin 1 on the display goes to pin 2 on the Arduino.
Picture 4) Pin 2 on the display goes to pin 3 on the Arduino.
Picture 5) Pin 4 on the display goes to pin 4 on the Arduino.
Picture 6) Pin 5 on the display goes to pin 5 on the Arduino.
Picture 7) Pin 6 on the display goes to pin 6 on the Arduino.
Picture 8) Pin 8 on the display goes through the 470 ohm resistor to the side rail on the bread board
Picture 9) Pin 9 on the display goes to pin 7 on the Arduino. Also Ground on the arduino is connected to the side rail on the arduino.
Picture 10) Pin 10 on the display goes to pin 8 on the Arduino.

If you have any question please ask them!

Step 3: Add the Probe/Antenna

Make the antenna/probe:
- Cut a 6-7 in. piece of solid core wire.
- Strip one end so you can plug it into your breadboard
- Strip the other end about 2 in. from the end.

Add the antenna: (Pictures 2-6)
- Take the 3.3M ohm resistor and connect it from the ground on the arduino to a point on the breadboard
- Add another wire from where the resistor is connected to analog pin 5 on the arduino.
- Add the antenna to where the resistor and the wire are connected on the breadboard.

Step 4: The Code

 Here's some basic steps to program your arduino.

1) Download the source code from below
2) Open the file in the Arduino IDE
3) Press the "Upload to I/O Board" button
4) Once the program is uploaded it will start running

Hopefully there are enough comments in the code, but if you have any questions, please ask them.

There is no difference between the .pde file & the .txt

Step 5: Play With It!

Now go measure EMF's! Here's a few ideas:
- Your dog/cat
- You
- Computer
- Cell phone
- TV

Make sure to use common sense, I'm not responsible for any damage to you or your arduino!

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    45 Discussions


    Question 4 months ago on Introduction

    where does display pin 7 connect to arduino please


    Question 11 months ago

    hi . my problem is the distance between the
    detection circuit. For example, if I find 220 volts at a distance of 10
    centimeters in normal mode, I want to change the distance between 1 cm to 10 cm with 2 keys or one potanseometr or ...


    1 year ago

    How small of an element can the emf sensor detect(elements in soil such as nitrogen etc.)


    2 years ago

    Oh common, i can not get it to work. I have a 7 segment led display, but my pins are a bit different than yours in the photo. I have added a website which shows how my pins look like. Every time i give it to something that emits an electromagnetic field, it just flickers. Will you help me please?


    3 years ago

    A couple of question if you are still answering. Sorry first ever project

    Can with be done with double digits display? ( want to use 2 nixe tube display)

    Can you run the led bar graph along side the display?

    Can you use a surplus wifi antenna as the antenna?


    3 years ago

    I didnt use the 3.3M and my Atmega328P is burnt out !?


    3 years ago

    Can you replace the 7seg with an LED bar graph?


    3 years ago

    Why 3.3M ohms specifically?


    3 years ago

    What kind of range do you get for a human hand? How close where you when the detector first went to a 2 level? Were the distances linearly proportional to the numbers, or were the number zones smaller as you got closer? Does the direction that you approach the antenna for make any difference? Do you think if you expanded the code, could you get 1024 different touch zones out of one resistor? Because if you could then, WOW! I am definitely planning on making this.


    3 years ago

    Will this detect wifi?

    Eng HowT

    3 years ago

    can i use others Analog pin?


    3 years ago

    This is cool! I just have one question, Where did you get 3.3 M Ω resistors?

    1 reply

    What units does this Arduino measure the electric field in? Is it Volts per meter or something else?


    4 years ago on Introduction

    Can I shorten the lenght of the antena? or there's a minimum length for it to work?


    9 years ago on Introduction


    Can someone explain, what are the components being utilized for the sensing coil/ wire, who pick up the emf, i dont see any Inductance coil, is it built into ATMega 328??

    also, it would be really grat if someone explains how does this emf sensor works.

    Thanks in advance