I have received a RPi 3 kit as a gift with tons of sensors, cables, resistors, etc.

I have managed to get the typical LED demo working by following literal instructions but I don't understand how to e.g. connect of the sensors.

How do I know which resistor to use, and to which GPIO pins to connect them?

  • 3
    Welcome to Raspberry Pi! Please take the tour and visit the helpcenter to see how things work here. This question is pretty broad and thus likely a bad fit for Stackexchange. However I would like to recommend to check the MagPi for some inspiration and plenty of tutorials. Really worth a look!
    – Ghanima
    Aug 28, 2017 at 19:23

1 Answer 1


To calculate the resistor you need to know some parameters regarding the LED.

Normally a red LED has a forward voltage of approx 2volt and a current of 20mA and the output from the Raspberry Pi is 3,3volt.

This means that 1,3volt (Raspberry voltage - LED voltage) and 20mA is the values for the resistors. then lets take 1,3v/0,02A = resistor (65ohm).

And what GPIO pin to use, well that's up to which pin you fancy in the programming.

Take a look at this video series, that will explain a lot: https://www.youtube.com/watch?v=OR5h0UnMcUE

Table for LED,voltage vs. color


  • There is also a some well written books, search for "electronics for makers"
    – MatsK
    Aug 28, 2017 at 19:17
  • Thank you, those are the figures I was looking for to get started.
    – Bob Dem
    Aug 28, 2017 at 19:17

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