Instructables
A while back I saw an EMF (Electromagnetic Field) Detector at makezine.com 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:

Picture of The Stuff:
The parts & tools.

Parts:
- 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

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

Step 2: Wire the 7-Segment LED Display

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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!
JoseG2yesterday

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

thexplanet4 years ago
Hello,

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
The arduino just picks up random signals (cosmic radiation, tv, etc.) In fact, the arduino uses empty analog ports to calibrate it's random number generator
This does not detect a Magnetic field...  It is a rather crude E-field detector.

That also explains why there is no coil used.

All it does is extend one of the analog inputs from the Arduino and allow stray electrostatic fields to be coupled to the A/D converter in the Arduino.

The 3.3 Meg resistor is used to "bleed-off"  excessive charge by reducing the impedence of the input.
Blaneparker2 years ago
Conner Cunningham is Collin Cunningham
i made mine with 3 1meg ohm resistors becouse thats all i have but it should work the same way but its not working.
owen1023 years ago
does anyone know where i can find plans for one that does not use an arduino?
if you can build it with arduino and get it to work you can simply remove the Atmega IC from your arduino and build it into a stand alone device, youll just have to get the schematic for you Arduino chip and wire it how you wish.
Wally_Z3 years ago
If I were to wire this without Arduino how would I do that?

Also, is it possible to use one of these displays without any kind of IC? I am a noob to this kind of thing and would like to know if you could just put a certain amount of power to certain pins to make it work instead of doing the whole IC and coding and all that wonderful stuff.
''balls''
thefan9903 years ago
My numbers are showing. The display is garble.
ffsman3 years ago
I tried it but instead of LED I set it to print to serial... I get only 0-2 in results whatever I measure,... only if I take antena in a hand it shows more than 50
Hook up a speaker instead of a segmented display, and you have yourself a theramin.
mbudansky4 years ago

can i use a 4.7m resistor insted of a 3.3 resistor?

No because if you did, you wouldn't get a accurate reading.
I would love to try that with my pc joystick port. Have to use an extension cable so pc does not affect results.
I really enjoyed this one and had a few thoughts because this has some great possible applications in ghost hunting. 1. replacing the wire antenna with a halls effect sensor. 2. lcd and/or computer read out 3. temp. sensor added (would be real easy considering the pins are open for sensor, ref. http://www.instructables.com/id/Temperature-Sensor-Tutorial/) 4. put a time stamp on any pre set spikes 5. data logger with sd card and up loading capability when connected to pc would be interesting to see if these are possible.
Ghost hunting? Are you kidding? You don't really believe in ghosts, do you?! O_o
dunnos4 years ago
 I like the code! I learned quite a few things! (for instance, how you make subroutines) thank you!


leemck4 years ago
This is a neat project that needs pointers to the underlying physics.

      It would be really neat if there were some reading material that would help explain what is going on when the project detects an electric field.

Is there a way to generate a "1 unit electric field"?  

Could one use a bunch of antennas, each wound with a different inline loop forming different inductances to pick up different frequencies of electric field?

 When there is a static charge on an object, it creates electric fields.  What is being read is the electric field, or potential a distance away from a charge object.  this isn't picking up frequencies, only stray electric fields, which are different than self propagating Electro-Magnetic waves, otherwise known as photons, or light, or radio waves.
 Did I mention that this works as a good proximity detector in drier climates where there is a lot of static charge buildup?  Just don't discharge onto the arduino- same for all electronics.
devenda4 years ago
I have a other 7-segment display and other pins can you tell mee what arduino pin connects to which segment(a,b,c,d,e,f,g)?

Thanks!
devenda4 years ago
funny and good instructable.
But it isnt very portable...
Is there a way to let it work on batteries?


Axaj devenda4 years ago
Yes, just hook up the batteries to a 2.1mm barrel jack (center positive, I believe).
emedina944 years ago
kool
 
Zafthan4 years ago
Great instructable, I was actually searching for something like this a few days before you posted it.