A sea of electromagnetic noise surrounds humanity, coming from countless electrical devices. Have you ever been curious about that noise? For my competition entry, I’ll show you how to build a simple EM detector so that you can listen in and learn more about your environment, and use it to receive an activation signal (for a motor). I have also included additional demonstration videos below. The detector circuit will require:
- 1x LM393 voltage comparator IC
- 2x 1M ohm resistors
- 1x 1K ohm potentiometer
- 1x 10K ohm potentiometer
- 1x Battery pack
For the output circuits, I also used:
- 1x 1uF capacitor
- 1x stereo plug board
- 1x PN2222 transistor
- 1x 1N4007 Diode
- 2x 1K resistors
- 1x 5v DC motor
- PC Speakers
In the following video, I will show you how to build the circuit, explain how it works, give a demo, and perform my signal presentation (note: updated 9/11).
The next videos feature a more advanced version of the detector, utilizing upgrades including a circuit board, better components, solder joints, a 3D-printed enclosure, and improved isolation. The core circuit is basically the same as the one featured earlier and uses the same principles. However, the signals are a lot cleaner. More demo videos can be found on my Youtube Playlist.
First, let’s evaluate some power supplies and see what kind of EM noises they give off during operation.
Next, let’s listen in on a Nintendo 3DS and see what it’s radiating. Notice how distinct noises emanate from different areas of the device.
Next, let’s test some audio cables and see how well their shielding works. This is a great practical use for the EM detector!
Next, let’s see if the EM detector has biofeedback capabilities. In this video, I think I heard my heartbeat.
Finally, let’s dive deeper into the proximity detection I demonstrated in the competition video. This time I’ll use a Tesla coil and evaluate how the signal changes as I move through different areas. There’s a lot more going on here that simple signal blocking.
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