This tutorial from ScratchMyPi shows you how to use scratch and a raspberry pi to make LEDs light up:
Simon Walters at Cymplecy has modified Scratch so it can be used to control the GPIO pins.
In this tutorial, I will show you how to control the LEDs through Scratch and the Pi.
Install Scratch GPIO
Follow the instructions at Cymplecy to install Scratch GPIO on your computer. Once installed, start it up and you’ll see it looks similar to Scratch.
Resistors (typically about 400 ohm)
Wires – female to male
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