Keyring light

youmagine

This is a DIY project that consists of three printed parts, an LED and a battery. The dimensions of these two parts are crucial: the LED should have a diameter of 4.8 mm with a rim at its base measuring 5.4 mm in diameter and 1 mm thick, while the CR1220 battery must be 2 mm thick and 12.3 mm in diameter. To print this project, I used an Ultimaker 2 and sliced it with Cura using the following settings: layer height of 0.1 mm, infill of 40% (although 20% might make top surfaces less smooth), and a print speed of 40 mm/s (80 mm/s also works but doesn't look as good). The three printed parts are: lower cap, upper cap, and slide. They all fit snugly together, requiring some post-processing to ensure they work smoothly. I used a nail file, a coarse file, and a round file that's the diameter of the LED (although smaller files or fine-grained sandpaper wrapped around a big nail would also work). Filing is necessary for several parts: the outside of the lower cap ring, especially its top; the insides of both the lower and upper cap rings; and the sliding parts of the slide and upper cap. A thin nail file is particularly useful for this last part. To ensure the keyrings fit through the vertical slots in the slide, you'll also need to file: the keyring-holders and the inside of the keyring-holder holes on the slide. The legs of the LED need to be prepared before assembly. First, they should be bent outward at their base so they're not too close together to fit across the battery. This is especially important for the upper leg, as it will prevent it from touching the battery at its base. Next, the leg that goes into the lower cap needs to be bent back a bit, while the other leg should be bent back in and then out again, with the second bend at about 6 mm from the base of the LED. This is the most crucial measurement. Assembly involves placing the LED in the lower cap, followed by the battery (preferably with its rubber ring at the top). Make sure the LED and battery are aligned correctly before assembly (and bending), as they only work one way around. Next, place the upper cap over the LED-ring of the lower cap at an angle, then move it down at the back. Finally, slide in the slide at the back, with the keyring-holders passing through its vertical slots. Make sure the LED leg goes into the tiny hole on the cylinder. The slide cap will now hold the lower and upper caps together. You might need to slide them back and forth a few times to smooth out the sliding surfaces. If the LED doesn't turn on when you move the slide, readjust the bends of the LED legs. To prevent the mechanism from disassembling itself, put something through the keyring-holders, such as a key ring.