How to wire a 12 volt relay switch

Written by david sandoval
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How to wire a 12 volt relay switch
. (12 volt relais, relay image by Sascha Zlatkov from Fotolia.com)

Relays are electromagnetic switches that switch between a "normally open" condition and a "normally closed" condition. Relay switches are used to switch a high-voltage or high-powered circuit by using a low-voltage circuit to actuate the switch mechanism. When the relay is actuated (or energised), the "common" terminal is switched from the "normally closed" to the "normally open" position. When the relay is turned off, the "common" terminal is switched back to the "normally closed" position.

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Things you need

  • One 12V SPDT (single pole, double throw) relay
  • One SPST (single pole, single throw) switch
  • One 12V power supply
  • One 100kΩ resistor
  • Electrical wire
  • Electrical pliers
  • Soldering iron
  • Electronic (rosin core) solder
  • Digital multimeter

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Instructions

  1. 1

    Cut seven lengths of wire, and strip each end of each wire of ½ inch of insulation. Attach one end of the first wire to the positive terminal on the power supply. Attach the other end of this wire to one of the terminals on the SPST switch, and solder the wire to the terminal. Turn the SPST switch to the off (open) position.

  2. 2

    Attach one end of the second wire to the free terminal on the SPST switch, and solder the wire to the terminal. Connect the other end of this wire to the relay coil (85) terminal, and solder the connection. Attach one end of the third wire to the remaining relay coil terminal (86), and solder the connection. Connect the free end of the third wire to the negative terminal on the power supply.

  3. 3

    Connect one end of the fourth wire to the relay common terminal (30), and solder the connection. Connect the other end of this wire to the positive power supply terminal. Connect one end of the fifth wire to the "normally open" relay terminal (87), and solder the connection. Connect the other end of this wire to the first resistor lead, and solder the connection.

  4. 4

    Connect one end of the sixth wire to the second resistor lead, and solder the connection. Connect the free end of the sixth wire to the negative power supply terminal.

  5. 5

    Connect the red (positive) multimeter probe to the first resistor lead. Connect the black (negative) multimeter probe to the second resistor lead. Turn on the multimeter, and set the scale selector to "Volts DC." Turn on the power supply. View the multimeter display; the voltage reading should be zero.

  6. 6

    Turn the SPST switch to the on (closed) position; you should hear an audible click. View the multimeter display again; the voltage should be 12 volts.

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