Tag circuit

LEDs and Resistors


In a previous post, I mentioned that you need to use a resistor when connecting an LED to the GPIO, but how do you know what value resistor to use?

The reason we need a resistor is because the LED will only stand so much current before it blows.

There are 2 output voltages from the GPIO pins, 3.3v from pins 1 and 17, and 5v from pins 2 and 4.

Lets say you have a 5mm blue LED from maplin (Something like this) there are 2 important bits of information you need to calculate the resistor to use with it. The Forward Voltage and the Forward Current.

Using GPIO

Breadboard - no wires

When using the GPIO I would recommend getting a breadboard and an Adafruit Pi Cobbler Breakout Kit. This will allow you to easily connect the Raspberry Pi to a breadboard so you can quickly and easily build circuits.


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