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How to Make a Simple Electronic Metal Detector

An electronic metal detector relies on electromagnetic induction to detect metal. This principle of electromagnetism describes the production of voltage in a metal object when it moves through a magnetic field. The metal detector detects this voltage as an electromagnetic signal, which then may be converted into an audio signal. You can demonstrate the principle of induction by building a simple electronic metal detector from ordinary household items.

Things You'll Need

CD case
Ruler
AM radio (pocket-size)
Calculator (solar-powered)
Scissors
Velcro
Metal object

Instructions

- 1
  Remove the plastic insert from the CD case that keeps the CD in place. Measure out a space on the backs of the calculator and radio where you can fit a piece of Velcro.
- 2
  Cut a piece of Velcro that will fit the space on the back of the radio, and another for the back of the calculator.
- 3
  Stick one of the loop pieces of Velcro to the back of the radio and place the corresponding hook piece on one of the interior sides of the CD case. Repeat this procedure with the calculator, placing the corresponding hook piece on the other interior side of the CD case.
- 4
  Attach the calculator and radio to the CD case by pressing the matching pieces of Velcro together. Turn the calculator and radio on. Switch the radio to the AM setting and turn the volume all the way up. Tune the radio to the highest possible AM frequency and slowly tune it back down until you hear only static.
- 5
  Bring the radio and calculator together by slowly folding the CD case closed until you hear a distinct tone from the radio. Slowly open the CD case until you are barely able to hear the tone. Keep the CD case open at this angle and move it towards a metal object. You should hear a loud tone when the metal detector gets within a few inches of the metal object.

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