How to Use a 9V Battery for a 3V LED

Written by jonathan cadieux
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How to Use a 9V Battery for a 3V LED
LEDs help light up the world we live in. (Jupiterimages/ Images)

LEDs are light-emitting diodes that emit light when electricity is applied, similar to a light bulb. LEDs are part of a group of lighting technologies called solid-state lighting and come in multiple styles, colours and light temperatures. LEDs provide greater energy efficiency than both incandescent and fluorescent lamps, and have a longer life cycle. A standard 3-volt LED lamp can be connected to a 9- volt battery, provided that a current limiting resistor is connected between the battery and LED.

Skill level:
Moderately Easy

Things you need

  • Calculator
  • LED current requirement
  • 9-Volt battery connector
  • Soldering iron
  • Resistor
  • SPST switch

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  1. 1

    Calculate the value of the resistor needed by dividing six volts by the LED 's current requirement in amps. The value calculated will be the resistor value in ohms. Use a resistor as close to this value as possible. Six volts is the remaining battery voltage across the resistor when there is three volts at the LED.

  2. 2

    Solder the positive wire of the battery connector to one lead of the resistor. Solder the remaining resistor lead to one connection on the switch.

  3. 3

    Solder the positive lead of the LED to the remaining switch connection. Solder the negative lead of the LED to the negative wire of the battery connector.

  4. 4

    Verify that the switch is in the "off" position. Connect the battery connector to the 9-Volt battery. Turn the switch to the "on" position and verify that the LED illuminates.

Tips and warnings

  • Always verify all connections are correct prior to applying power to the LED
  • Use caution when soldering - irons are hot and can cause burns.

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