How to Design One Way Switch Electrical Circuit

Written by kevin krause
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How to Design One Way Switch Electrical Circuit
A light switch, an example of a SPST switch (light switch image by Jim Mills from

A one way switch electrical circuit is the most basic form of switching circuit. It is centred around a single-pole single-throw (SPST) switch, which has two positions. One creates a break in a circuit while the other closes the circuit allowing current to flow freely. The other two basic components of the one way switch circuit are a power supply and a device to be operated with the switch. This type of circuit is used for almost any lighting circuit, and it is also the circuit used for a doorbell. The doorbell is a special type of SPST switch known as a momentary switch. Designing and building a one way switching circuit is easy once you understand its basic construction.

Skill level:
Moderately Easy

Things you need

  • Power supply
  • Wire
  • Switchable device

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  1. 1

    Connect a wire from the positive terminal of the power source to one terminal on the switch. Since the switch is always either on or off, the terminal you use does not matter.

  2. 2

    Run a wire from the second terminal of the switch to the positive terminal of the device the switch controls. In the case of a light bulb circuit, the wire would be connected to the positive terminal of the bulb socket.

  3. 3

    Connect a wire from the negative terminal of the device (light bulb socket) to the negative terminal of the power supply.

  4. 4

    Operate the device by switching between the two positions on the switch. In the light bulb example, one position will send power to the bulb, illuminating it, and the other position will break the signal path, keeping the light off.

    How to Design One Way Switch Electrical Circuit
    Light bulb, the result of a switch in the "On" position (light bulb image by Sheldon gardner from

Tips and warnings

  • Since the switch simply controls whether a circuit is open or closed, it could be positioned along the negative line returning from the device. This wiring is not uncommon.
  • As is the case with any electrical wiring, be sure the power supply is shut off before making any alterations to avoid the risk of electrocution or other injury.

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