Tag Archives: EMF Detector

Building a smartphone EMF detector with an electret mic and Arduino

A simple Arduino circuit can enable you to see a smartphone’s electromagnetic activity, even while it’s “asleep.”

As ubiquitous as smartphones have become, the jury is still out with regards to how their signals affect our bodies. Radio frequency energy is a form of electromagnetic radiation, which can be categorized into two types: ionizing and non-ionizing. Exposure to ionizing radiation, such as from radiation therapy, is known to increase the risk of cancer. However, although many studies have examined the potential health effects of non-ionizing radiation from electronic devices, there is still no consistent evidence proving it is detrimental to our health.


With this in mind, Epic Jefferson decided to call attention to smartphones’ electromagnetic activity, even when the phone is “asleep.” The project had been part of a Making Things Interactive course at Carnegie Mellon University, which encouraged students to use Adafruit’s electret mic to take something from the background environment and bring it to the forefront in a non-invasive way.

“The first thing I remembered was that the RadioShack phone pickup that I have made some interesting noises when held close to any electronic device. Since this thing is essentially just like a guitar pickup (just a copper coil wrapped in a circle), that means it’s sensitive to disruptions in it’s electromagnetic field. If a phone can interrupt it’s EMF, we can use that to trigger an action to visualize the phone’s EMF activity,” Jefferson explains.


Although the RadioShack device worked well for converting EMF activity to the audio spectrum, when it came to passing that into the electret mic and then into the Arduino Uno (ATmega328) for processing, it became highly susceptible to noise coming in through the mic. With a simple adaptation of the circuitry and code using fellow Maker Aaron Alai’s EMF detector project as a reference point, Jefferson was able to make it sensitive enough to detect the small electrical pulses emitted by any smartphone.

With the electronics all squared away, the Maker decided to house the components inside of a Walnut enclosure. After about 10 hours of milling, sawing and sanding, the project was complete.

Want to create an EMF detector of your own? The modified code can be found on GitHub here.