A simple little light I made to put in a fancy bottle of tequila. It is activated by twisting the lid on, which in turn presses the contact into the battery, causing the LED to illuminate.

To make this you'll need:

• Screw Top Bottle with a 17.5mm internal neck diameter*
• 10mm LED
• 3 coin cell batterys (8mm OD) (I nicked mine from a cheapy plastic candle)
• long nose pliers
• and a 3D printer obviously

Assembly:

• Cut a leg of the LED to a few mm and bend over, make sure it can't touch the other leg.
• Bend the other leg as shown in the picture, it can be tweaked later.
• Put the LED in the part, long leg first, the LED slides in sideways. Once centered twist the LED so the long leg aligns with the slot.
• Put the battery in (the right way round) from above, you may need to lift the leg up slightly.
• Bend the leg so it is held sprung, 1mm above the top of the battery.
• Pop into the bottle and put lid on. Tweak if necessary.

It's not the brightest light but can be a useful torch if getting up in the night and don't wish to stir your other half. Also it's just a cool use of old bottles you want a reason to keep.

*The design can be easily tweaked for different bottle neck diameters, let me know if you want me to put up a version with a different size for you.