• The longer lead goes to the more-positive voltage
• Current goes in one direction, from the anode (positive) to the cathode (negative)
• LEDs that are ‘backwards’ won’t work – but they won’t break either

It’s all a little confusing – we often have to think about which is which. So to make it easy, there’s only one thing you need to remember and that’s the LED wont light up if you put it in backwards. If you’re ever having LED problems where they are not lighting, just flip it around. Its very hard to damage an LED by putting it in backwards so don’t be scared if you do

If it helps, refer back to these photos and diagrams or print them out for your reference

All the different sizes and colors

One of the best things about modern LEDs is all the colors they come in. It used to be that LEDs were only red or maybe yellow and orange, which is why early electronics from the 70s and 80s only had red LEDs. The color emitted from an LED has to do with what type of material they are made of. So red, for example, is made with Gallium Arsenide. Since then, scientists have experimented with many other materials and figured out how to make other colors such as green and blue, as well as violet and white. (You can see a massive table of all the different materials used to make LEDs in the wikipedia page )

When we first started making electronics in the late 90’s, we bought some 5mm blue LEDs and they were $3 each. Now you can get easily a dozen LEDs for that price. Life is good!

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