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How to Build a Seismic Detector Using a Geophone

Geophones are devices that consist of a weight hanging on the end of a spring. They detect earthquakes and other earth movement ̵1; even the footsteps of a passer-by ̵1; by attempting to remain motionless and plumb straight as the ground moves. When suspended between the walls of a magnet, the geophone generates a fluctuating electrical voltage that is proportional to the ground movement. This voltage can be transmitted to a receiver that displays it in an analog or digital version. Adaptations of this principle have produced geophones for use in underground surveys, oil, gas and mineral exploration, as well as the monitoring of earthquakes and nuclear explosions.

Things You'll Need

Low cost geophone from manufacturer
LED light display unit with two connector blocks
Nine-volt battery with snap-on connection
Electrical connector wire
Wire stripper
Soldering gun
Power connection
Solder wire
Alligator clips
Metal base plate, approximately 6 inches by 4 inches
Double-sided adhesive tape

Instructions

- 1
  Examine the geophone̵7;s top surface and locate the anode and cathode. These are the terminal points for the electrical connection between the geophone and the LED display box.
- 2
  Remove 1/4 inch of plastic insulation from each end of four separate lengths of connector wire using the wire strippers. Plug in the soldering gun and leave it to heat. When the soldering iron is hot, place one end of the solder wire and one length of the connector wires at the geophone anode and solder a connection. Repeat the process at the geophone̵7;s cathode.
- 3
  Attach the wires from the geophone to one of the connector boxes on the LED light display unit using one alligator clip for each connection. Ensure that the polarity of the connection is correct. The positive connection (the anode) is the outermost connection of the LED display box for each connection block.
- 4
  Place the snap-on connector of the battery over its two terminals. Attach the ends of connector wires to each battery terminal with alligator clips. Attach the other ends of the connector wires with alligator clips to the second connection box on the LED display unit.
- 5
  Stabilize the geophone by attaching its geophone base to a flat, rectangular metal base using double-sided adhesive tape.
- 6
  Walk alongside the detector and watch the LED display light up as the geophone responds to the ground vibration caused by footsteps.

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