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Weekend Workshop: Detect radio waves (and nuclear detonations) with this DIY coherer

weekend workshop diy energy detector 032616
Need something to keep you busy this weekend? Look no further. The Weekend Workshop is our weekly column where we showcase a badass DIY project that you can complete with minimal skills and expertise. We’ve dug through all the online tutorials on the Web, and gone the extra mile to pinpoint projects that are equal parts easy, affordable, and fun. So put on your work pants, grab your tool belt, and head to the garage — it’s time to start building!

These days, impressing your friends with bleeding-edge technology means showing off your new iPhone or talking to your computer and having it search the Web for you. Unfortunately, most of your friends probably have that phone already or (more than likely) have something better. What ever happened to the diversity of show and tell? Well, thanks to an ingenious look to the past, an Instructables user may have actually found the one device capable of impressing your friends: a coherer energy detector.

Coherer Test

Using a technique made popular during the early 1900s, Instructables user Narzan Qarma devised a way to fashion an ancient radio signal detector into something capable of sensing a very high level of energy. Comprised of little more than some metal powder, a 3V battery, and a bit of electrical wiring, a coherer energy detector might be one of the easiest (and most unique) weekend projects we’ve seen.

But what exactly would you use it for? Qarma’s own plans dub the sensor a nuclear explosion detector, capable of sensing the electromagnetic pulse given off during a nuclear detonation. While this function might seem a tad extreme, the device also has the ability to detect strong radio frequency energy, or any electrical pulse emitted nearby.

Though relatively scant on required materials, Qarma’s old-fashioned technique allows the device to work surprisingly well. Moreover, how it manages to recognize energy is incredibly straightforward. Whenever strong enough RF energy is emitted, the shaved metal filings inside the canister cling together and bridge a gap in the simple circuit, tripping the LED light.

To help you get a head start on constructing your own DIY energy sensor, we combed through Qarma’s Instructables walkthrough for all the tools, materials, and otherwise needed for the project. With as straightforward and easy-to-follow as the method is, you’ll have the ability to actually wow your friends with this old (but new) tech in no time. Here’s everything you’ll need to get started:


  • Knife
  • Screws (2)


  • Small LED light
  • Electrical wire
  • Sheet of plastic paper
  • 3V battery
  • Transformer
  • Plastic film container

With all the necessary tools and accessories at the ready, it’s time to start putting together this novel energy detector. Just follow the quick walkthrough posted to Instructables by user Narzan Qarma and before you know it, you’ll have your own unique energy sensor. Happy building!

The step-by-step walkthrough on constructing this coherer energy detector can be found here.

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