The LED – Christmas Lights

The LED is probably the most well known electronic component as it is the component that you can see on a device. It is often used in devices to indicate a particular mode or show you that the device is powered and turned on. Although LED’s have been available 40 years they are still becoming increasingly popular in devices such as car headlights, and ceiling down lights due to their increased electrical efficiency and physical size.



  1. Identify all components required from parts list and assemble series circuit following breadboard layout and schematic diagram.
  2. You might find that the circuit does not work with 3 LEDs in series and need to reduce the circuit to two LEDs
  3. Take measurements of voltage across each LED and then across the whole circuit from the positive side (anode) of the first LED to the negative side (cathode) of the last LED.
  4. You should notice that the reason the third LED did not work was because a 4.5V power source was not enough voltage to light all three LEDs in series as each LED used around 2V.
  5. Repeat these steps to assemble and measure the parallel circuit.
  6. Think about the differences in brightness of each LED in the parallel circuit. also think about what would happen if you removed the green LED from each circuit.
  7. discuss your findings in your learning journal.

Diagnosing problems:

  • If any component is getting hot disconnect the battery.
  • Ensure a resistor is used in the circuit or LED will be burned out and damaged
  • Ensure LED positive leg (longest) is connected to positive side of circuit
  • Check battery voltage with multimeter in Volts DC mode
  • Try a different LED in case it has been burned out (ensure you are using a resistor!)
  • Look at breadboard picture bellow and ensure all connection are correct.

Parts List

Part Qty Name
VCC1 1 4.5V – 6V Battery Supply
R1-3 1 330 Ohm Resistor
LED1 1 Red LED 5mm
LED2 1 Green LED 5mm
LED3 1 Yellow LED 5mm

Fritzing Breadboard Layout and Schematic Diagram:

SeriesSeries Circuit Fritzing Breadboard

Series Circuit Schematic

Parallel:Parallel Circuit Fritzing Breadboard

Parallel Circuit Schematic


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