Christmas Light Tester

Avoid the pain of trying to find which of the bulbs in a string of Christmas lights are blown with this cool Christmas light tester. All you need is a few components, and this cool circuit will save you many hours of frustration.

The piece of wire acts as an antenna and the LED lights up when it is in close proximity to a wire, that has voltage in it. As you run the antenna along your string of Christmas lights, the LED will turn off when no voltage is detected, and therefore it will turn off directly after the light bulb that is blown.

Cool circuit right ?


Components required

  • 1 x Piece of wire
  • 1 x 10MΩ Resistor
  • 1 x 4.75Ω Resistor
  • 1 x 475Ω Resistor
  • 1 x 50kΩ Variable resistor
  • 3 x MC14069 Inverter
  • 1 x BC548B Transistor
  • 1 x LED



Christmas Light Tester
Christmas Light Tester