Light-emitting diodes – commonly called LEDs– are found in several your MakeCrate projects. They come in a range of colors, sizes, and intensities. Our directions and videos emphasize that the LEDs must always be connected in the correct direction, and if you reverse one in a circuit, you’ll see that it no longer works. Let’s look at what is going on inside and LED that makes it work like that.

First, we’ll start with some vocabulary.

A diode is an electrical device that allows for the current to move through it in one direction.

A semiconductor is a material that allows electricity to pass through it partly. This is different than a conductor, which allows electricity to flow freely, and an insulator, which allows almost no electricity to pass through.

So, an LED is a diode that contains two types of semiconductor material inside. On one side, there is p-type material, which contains positively charged particles called “holes”. On the other side, there is n-type material, which contains extra electrons, which are negatively charged.

When an LED is inserted into a circuit, it must be done so that the side containing the n-type material is on the negative side of the circuit while the p-type material must be on the positive side.

When electric current flows through the circuit, the electrons from the n-type material and the holes from the p-type material can move towards the other side of the material.

Once the holes and electrons are in motion, they begin to interact, and this interaction causes the release of energy as photons, which we see as light.

The types of material in the semiconductor determine what color light the LED emits.

Got questions? Post them in the comments below.