It’s that time of year again, when many the world over chop down a tree, then insert it into some sort of water dish to keep it green for a month or longer. This normally works out well, but means that someone has to keep it hydrated, climbing under sharp branches to intermittently check the water level.

As originally seen on Reddit, this is a perfect job for Arduino, and with some very simple wiring, maker “Boskovitch” created a clever setup that shows water levels with three blue, yellow, and red LEDs. A depth sensor in inserted into the water, which feeds analog readings to an Arduino Nano that is used for control.

Threw this together last night for my dad. He’s very anal about keeping his tree healthy, and he gets on his stomach and sticks his hand in the base to check the water level a couple of times a day. So I threw this together so he doesn’t have to crawl under the tree anymore. After the semester is over I might add an automatic watering system with a solenoid valve and gravity feed.

Want to recreate this setup for your own Christmas conifer? Check out Boskovitch’s write-up here.

[Jason] and his father took advantage of a week off of work over Thanksgiving to design and build a Christmas light decoration that can flash fancy patterns. He calls it the Uno Christmas Tree. It’s sixteen strands of lights draped between a pole and the ground to form the shape of a tree. The main controller is an Arduino UNO, but what really makes this work is a mechanical relay board with sixteen channels.

Using trigonometry they figured out that the decoration would be fifteen feet tall and have a five-foot radius at the base. A pipe was installed to act as the trunk, with an old toilet flange at the top and stakes at the bottom to anchor the lights. They all make their connections at the controller box using extension cords that were labelled with channel numbers. You can see the final product in the video after the break. But you’ll also want to watch the clip on [Jason's] blog which shares the sonic symphony created when the mechanical relays really start working.