Light Emitting Diode

Project Number: 18

Description: Build the circuit shown. Set the meter (M6) to the 50mA setting. For each of the slide switch (S5) positions, push the press switch (S2) to measure the current through one of the LEDs (D1 & D5). Then change the slide switch (S5) position to measure the current with the other LED, and compare them. Now set the meter to the 5V setting, and compare the voltage measured with each LED. The voltage for both should be lower than what you measured directly at the battery in the preceding project, due to the voltage needed to turn on the LEDs.

Snappy: Light emitting diodes (LEDs) are one-way lights with a turn-on voltage threshold. If the voltage is high enough, they will light. The yellow LED (D5) requires a higher voltage to turn it on, but can get brighter. When electric current flows through an LED, energy is released as light; the color depends on the material. LEDs are much more energy efficient and last longer than ordinary light bulbs but were only used in low-power applications due to power limits, cost, and limited colors. However, LEDs are rapidly being improved and are increasingly being used in home lighting.