DIY Reed Switch

Written by john heller
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DIY Reed Switch
Reed switches commonly react to magnetic fields (12 volt relais, relay image by Sascha Zlatkov from

A reed switch is a electrical switch that is activated by a magnetic field. The function of the device is a electronic switch that only makes contact and completes a circuit when it comes in contact with a magnetic field. Used to trigger a siren when motion is detected, it is most commonly found as part of a burglar alarm. You can make a reed switch yourself using a few commonly found items.

Skill level:

Things you need

  • 3" piece of copper pipe
  • Scissors
  • Sheet of plastic canvas
  • Earth magnet
  • Zip ties
  • Spool of steel craft wire
  • Small bit drill
  • Pencil

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  1. 1

    Drill a small hole on one side of the end of the copper pipe. This will allow you to string and solder wires to the device after you have made it.

  2. 2

    Cut a 1/2 inch by 4 inch piece out of the plastic canvas.

  3. 3

    Wind a tight coil of steel wire around the pencil to create a spring. Wind it as tightly and as close together as possible.

  4. 4

    Attach the spring to the plastic canvas using a zip tie. Lay the spring on top of the cut piece of plastic canvas horizontally, all parts of the spring should be completely touching the plastic canvas. Run the zip tie through one of the gaps in the top left hand side of the plastic canvas. Tighten the zip tie around the spring so it is flush and firmly attached to the plastic canvas. Cut the excess plastic from the zip tie so it will fit inside the copper tubing.

  5. 5

    Insert plastic canvas, spring, zip tie combo into the copper pipe. Wrap the spring in the plastic canvas and insert it into the copper pipe. When a magnet is pulled close to the top of the pipe it will pull on the spring and make it touch the copper pipe. When the magnet is removed the spring will relax and the connection will be severed.

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