In this lession you will use perhaps the most common of all LEDs a 5mm red LED. 5Mm refers to the diameter of the LED and as well as 5mm, other common sizes are 3mm and the large fun 10mm LEDs.
You cannot directly connect an LED to a battery or voltage source. Firstly, because the LED has a positive and a negative lead and will not light if they are the wrong way around and secondly, an LED must be used with a resistor to limit or 'choke' the amount of current flowing through the LED - otherwise the LED could burn out!
There are two ways to tell which is the positive lead of the LED and which the negative.
- Firstly, the positive lead is longer.
- Secondly, where the negative lead enters the body of the LED, there is a flat edge to the case of the LED.