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DIY: Homemade Carbon Microphone

Microphones convert acoustical energy or sound into electrical energy. They are able to take the air vibrations and transform them into electrical vibrations. These electrical signals are modified by circuitry or software that can do things such as amplify or distort. Carbon microphones have carbon granules and a thin membrane. When the membrane vibrates, it squeezes and releases the carbon, causing its resistance to change. Since resistance affects the ability of currents to flow within a circuit, this changes the electrical signal that runs through the carbon. To make a homemade carbon microphone, use a pair of disposable cups as the vibrating membrane. Amplify the signal with PC speakers.

Things You'll Need

2 paper cups
Activated carbon granules
Aluminum foil
Glue
Alligator clips
Set of PC speakers

Instructions

- 1
  Cut a strip of aluminum foil that is from 1 1/2 to two times the length of a paper cup. It must be wide enough to completely cover the cup̵7;s bottom. Cut a second strip with the same dimensions. The two strips will serve as electrical contacts.
- 2
  Attach an aluminum strip to the inside of one of the cups. Apply glue to the inside bottom. Add a strip of glue inside of the cup on its right.
- 3
  Place a strip of foil inside the cup on its right side. The bottom must be completely covered. Press the foil against the glue on the cup̵7;s inner-right side. Press the excess foil so that it goes over the rim of the cup.
- 4
  Take the second cup, and turn it around so its bottom faces up. Apply enough glue so that the foil covers the bottom̵7;s surface. Add more glue down the outside of the cup̵7;s left. Attach the second aluminum strip so that it covers the bottom and goes down the left.
- 5
  Add glue to the top of the aluminum foil on the bottom of the first cup. Pour about 2 millimeters of activated charcoal inside.
- 6
  Apply glue to the bottom of the second cup, so it covers the aluminum foil. Place the second cup inside of the first, so it sits on top of the charcoal, with its aluminum strip facing left. Make sure the two aluminum strips do not touch.
- 7
  Test the carbon microphone. Use the alligator clips to connect the aluminum strips to the speaker̵7;s jack. Place your mouth against the microphone̵7;s opening, and hum or sing to hear it work.

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