Arduino EMF detector gets numeric

Arduino Technology
Arduino EMF detector gets numeric


One of the great things about remaking simple projects is the extra time they allow us to add enhancements and a personal touch. Instructable member computergeek swapped out the LED bargraph from my EMF detector to create a single-digit numerical display version. Good idea –

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 .

Thanks – I’ll pass that on to Conner next time I see him ;) Here’s hoping we’ll soon see a 3D graphical representation of nearby fields … mapped to augmented reality? … k, maybe that’s a bit of jump from a 7-segment – an LCD perhaps?


Making the Arduino EMF detector

6 thoughts on “Arduino EMF detector gets numeric

  1. Brian says:

    By using just a single resistor on the cathode of the 7-segment display like that, the display is going to be brightest when only a single segment is on, and will get dimmer as each successive segment is switched on.

    It’s more of a pain to wire up, but you’ll get better results using separate resistors for each segment, like the bargraph version.

  2. DB Speakers says:

    I’m an RF engineer and I really like the work that’s been done here; it’s a really cool idea. I think there’s a good chance I’ll be building one of these in the next couple weeks if I get around to it. If I never get around to it, I have a couple suggestions that may help it out.

    Consider adding a ground probe wire connected to the board ground. The voltage being detected is the field from the probe to the board ground. If you mounted the positive (probe) and negative (probe connected to ground) in fixed position relative to each other, readings should be consistent. You might even be able to capture field polarizations with a fixed configuration.

    At low frequency like this, the best bet for a field detector (think of it as an antenna) is 2 parallel plates. A couple of aluminum covered ping padles, or even the cutout bottoms of pop cans, would work as plates. Try separation distances between 10 and 100 cm.

    LED’s are passive elements that are efficient emitters at their designed wavelengths. Even when enabled, they shouldn’t be putting out anything but photons and thermal noise.

    An amplifier on the front end would allow you to look for specific signals. An audio amplifier would pick up grid and spark transients, but would filter out frequencies above the cutoff). It would also allow for tweaking the sensitivity of the probe.

    Hope this helps, good work.

  3. Philippe Teuwen says:


    I like all those EMF detector projects we saw recently, such a simple design and still very effective.

    Actually I attempted to use my LCD before realizing you suggested it, simply because that’s what I had available.

    Here is a pic with links to a video and code and explanations:

    Upper row is the averaged signal, lower row is the min & max of the signal, which give a much better view on the dynamics of the signal, check the video.


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