How to Connect a Switch to a 12V LED

Written by david robinson
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How to Connect a Switch to a 12V LED
Treat 12-volt LEDs just like bulbs in a circuit. (led image by sasha from

Voltages above 2 to 4 volts rapidly destroy LEDs unless a current-limiting resistor protects them. 12-volt LEDs consist of an LED and a built-in resistor designed to automatically reduce 12 volts to the value required by the LED. Their very long lifespan, cool operating temperature and physical robustness make 12-volt LEDs ideal replacements for traditional incandescent bulbs. Wiring them to a switch is a straightforward procedure within the capabilities of anyone who can use a soldering iron.

Skill level:

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Things you need

  • Wire cutters
  • 2 crimp-on terminal connectors
  • Crimping tool or strong pliers
  • Electrical insulating tape
  • Insulated 12-volt wire
  • Soldering iron
  • Solder

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  1. 1

    Identify the positive wire leading to the LED from the battery. If the wire polarity is not obvious, the LED may have positive (+) and negative (-) markings on the lower part of the unit. LEDs are polarised and, when working, they are the right way around and the markings will correctly identify the wires.

  2. 2

    Disconnect the battery. Use wire cutters to cut the positive wire at any convenient point between the battery and the base of the LED. Strip away the final 5mm of insulation from both ends of the severed wire. Unless both ends can reach the switch, extend the wires by soldering additional wire to the cut ends. To do this, remove the insulation from the ends of two extension wires of the desired length, twist the bare end of each extension together with the end of a severed wire and then solder them together. Cover the cooled joints in electrical insulation tape.

  3. 3

    Strip the final 5mm of insulation from the ends of the wires to the switch terminals. Slide a female crimp-on terminal over the end of each wire and crush it into place using a crimping tool or strong pliers. Attach the wire terminals to the male terminals on the rear of the switch.

  4. 4

    Check the wiring for errors, cover any exposed joints with insulation tape and ensure the wiring is not routed over sharp edges. Reconnect the battery and operate the switch.

Tips and warnings

  • Soldering iron tips are very hot. Take care not to touch them against skin or flammable materials.
  • The switch can be installed on either the positive or the negative wire, but switching the positive wire totally isolates the LED from the power supply when it is turned off.
  • Never solder a live wire. Doing so may damage both the iron and the components you are soldering.

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