Yesterday was the annual Christmas geocache event in the middle of a forest (GC4V00C). The last few years I’ve brought mini chemical light sticks to decorate the tree, but because of the cold they tend not to last very long. This year, I decided to upgrade and created little blinking lights to hang on the tree using some LEDs, batteries, tape and pipe cleaners.

I searched the Internet for flashing LEDs and found some that changed colours and flashed without needing and fancy circuitry. And they came in both slow and fast versions, so I ordered 15 of each.

Next stop was eBay to find some 2032 batteries. I’d bought some in the past from a seller near Toronto and happily he (?) was still selling them, so I ordered up a bunch.

Everything arrived in a timely manner, so Friday evening I started building my little lights.

The construction was fairly straightforward because basically you put a 2032 battery between the leads of the LED, being sure to respect the polarity, and tape the leads to the battery. A little bit of pipe cleaner wrapped about one lead — not both leads because that could short it out — acted as a hook.

The tricky bit was coming up with a way to pre-build them and be able to turn them on only once I had arrived at the event cache. After a little experimentation I settled on using triangular wedges of waxed paper. By sticking one between one lead and the battery and leaving the wide end of the triangle poking out, it was possible to gently remove the paper without undoing the tape.

The result was a festive tree in the middle of a forest…

I took a short video of the lights when I returned home in the evening before I took them apart for another day: