How to Use a Microswitch for Powering On & Off

Written by adam quinn
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How to Use a Microswitch for Powering On & Off
Switch tracks and activate other model railroad accessories using a microswitch. (Comstock Images/Comstock/Getty Images)

A microswitch is used for electrical applications that require small movements to open and close a circuit, such as model railroading and designing a computer mouse or joystick. A microswitch can be wired to power your circuit on, when the handle is pressed, and off, when released. This sequence can also be reversed to power a device when the handle is released. Install a microswitch at your model railroad turnouts, to switch tracks rapidly.

Skill level:
Moderately Easy

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Things you need

  • Alligator clip wires
  • Clamp
  • Small light bulb
  • Battery

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  1. 1

    Determine the location of the three microswitch terminals. One terminal should be labelled with a letter C, for "Common." The second terminal should be labelled with the letters NO, for "Normally Open to Common." The remaining terminal should be labelled with the letters NC, for "Normally Closed to Common."

  2. 2

    Connect an alligator clip wire between the C terminal on the microswitch and the negative terminal on a battery. Connect an alligator clip wire from the NO terminal to the thread side of a light bulb, or the positive end of another type of resistive element. Connect the bottom, or negative, terminal of the light bulb to the positive terminal on the battery, using an alligator clip wire. Clamp the clips to the top and bottom battery terminals.

  3. 3

    Press the microswitch lever to power on the light bulb. Release the switch to power off the light bulb.

Tips and warnings

  • If your application requires the circuit to be powered on, when the microswitch handle is released, wire the NC terminal to the positive terminal, or thread side, of the light bulb. Leave the NO terminal disconnected. When the switch is pressed, the circuit will open and the light bulb will power off.

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