Overview

This pack provides six LEDs, two each in red, yellow and green. In addition to the LEDs you will receive the current-limiting resistors required to prevent burning out the LED. With this assortment of LEDs you can perform experiments and become very familiar with interfacing LED outputs to your system. There are even enough LEDs and in the correct colors for you to simulate a traffic control system.

Details

What is an LED? Light Emitting Diodes (or LEDs) are electronic components that, like a regular diode, allow electrical current to pass in only one direction. They differ from normal diodes in that when current flows through them, they give off (emit) light. Just like regular diodes, LED's have a cathode and an anode. Current will only flow from the cathode to the anode, and will be blocked when trying to go from the anode to the cathode.

Use Cases

You can make an LED light up, by plugging one into your breadboard (learn more about breadboards at http://projects.granzeier.com/whats-a-breadboard/) and then connect a resistor and short hookup wire as shown below:

When you turn on your power supply (or battery), you will see the LED glow.

If you want to have your computer, or controller, turn the LED on and off, you would connect the hookup wire to the output port of your controller, rather than to the positive power rail. Then, when you want to have the LED turned on, you would program your controller to output a high (+3.3V or +5V) signal on that output pin. The output signal would take the place of the positive power rail and the current would flow through the resistor, through the LED and into the output pin (remember, the only things moving in an electronic circuit are electrons - and, with a negative charge, they are attracted to a more positive voltage.) This will cause the LED to light up. We use the resistor to limit the amount of current, so that we do not draw more current than the controller can safely provide.

In order to have your controller turn the LED back off, you would just output a 0 on that output pin. With the output pin set to 0V (or ground,) there will be no positive point to the circuit, current will not flow through the circuit, and the LED will stop giving off light.