Introduction: Electricity/EM Field Detector (simplest One)

This is a simplest EM field detector you can find on the internet. I designed it myself and it's explained how it works in the next step.

Basically what you will need, are two transistors some resistors, antenna for example made from a copper wire like mine, 3v coin battery, PCB, LEDs and a switch.


  • NPN transistor BC547 x2
  • 100 Ω resistor x2
  • 3.3kΩ resistor
  • Antenna (mine is from copper wire)
  • 3v coin battery
  • Coin battery holder (mine is 3d printed)
  • PCB
  • Switch
  • Any color led x2
  • optionally a cover

Step 1: How It Works?

This device basically catches EM field which is created in small amounts by electronic devices or power lines in walls and converts it into small voltage which makes bigger voltage flow through led. A coil u can see is basically an antenna. U can use it to see if there's electricity in something, or to find power cables in walls.

Step 2: Solder Everything on a PCB.

Get a PCB and just solder it on it in a way showed on a schematic. My version is powered by a 3 volt coin battery but yours can be powered by something else, just remember to change resistors.

Step 3: Done! Just Test It.

It should work just like in the video. When you bring it near to a power outlet, LED should light up. You can experiment with other transistors, resistors etc. LED blinks only in the video, I think that is because an AC voltage in the power outlet, leave your ideas in the comments!

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