LED’s are used in almost every electronic device we use today. Let’s take a look at how LED’s work, why they are used in many electronic applications, and how we can use them in our own projects. LED stand for Light Emitting Diode. If we were to zoom way in and take a look at the molecular level we would see a p-type material and a n-type material. Where these two material come together is called the pn-junction. When we connect our LED to a power supply we generate a supply of electrons on the n-type side and holes on the p-type side. We keep increasing the voltage until an electron jumps over to pair with a hole and in the process a photon of light is released.

Now it's time to make a LED light up. For this simple circuit we are going to connect a LED through a voltage source through a resistor. Unlike some other electrical components polarity is important when connecting an LED, which means it only goes in one way. Looking at an LED we can see that one leg is going to be longer than the other. The long lead is the anode, the positive side and the short lead is the cathode the negative side. So when we put the LED in our circuit we want the long lead to connect to the positive side of the power supply. 

LED’s come in a variety of types. There are single color LED’s and then there are RGB LED’s that have three individual colors in one package. RGB LED’s have more leads than their single color counterparts. There are normally three anodes for each color: red, green, and blue and one lead that is the cathode. But make sure you check your LED’s data sheet to verify your LED pinout.

If you watched my previous video about the resistor you know that if you connect an LED right to a power supply it will burn out. This is because we need a resistor in the circuit to limit the current that flows through the resistor. To do this we need to look to the LED’s data sheet and do some math. But don’t worry, this is going to be easy. First we want to look for two values in the LED’s dataset. The forward voltage and the forward current. The forward voltage is the voltage required for the LED to turn on and the forward current is the current that the LED is able to sustain without burning out. We can use this formula to calculate the desired resistance value.

((Source Voltage) - (Forward Voltage)) / Desired LED Current

Let's fill in the values we found from the data sheet then plug those into our calculator to find the desired resistance of 90 ohms. But no one wants to do the math these days so I have included a link below to the digikey website that has a nice LED resistor calculator on it.

LED Calculator:
https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-led-series-resistor

When dealing with RGB LED’s you will need to connect a resistor to each individual color, and do the resistance calculation separately since each color has a different forward voltage. If you want to make the LED dimmer just increase the resistance value! We sometimes want to use more than one LED in our circuit, and to do this we can simply hook them up in series one after another. 

LED’s are awesome! They are power efficient, small, and bright. I can’t wait to see what projects you build using out little friend the LED.