These recycled milk bottle lights look cool and seem to work really well. You can make a basic version with a simple on/off switch, or you can make a deluxe version that uses an Arduino to add fading and sequencing to the lights. Check out the link for complete build instructions and the source code for these funky recycled LED lights.

LED lighting in milk bottle caps. The PPE makes for good diffusion. They’re controlled by an Arduino Mini hooked up to a potentiometer. The arduino looks at the analogue reading from the pot and then depending on the value carries out instructions on which lights to turn on or off.

More about the Arduino controlled milk bottle LED lights

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Make: Arduino