LED Tree Brings Gravity to Christmas

Here’s a fun entry into our coin cell challenge. The power source is the actuating force in [Frank]’s blinky LED Christmas tree, which takes advantage of the physical structure of coin cells and our old pal gravity to roll out some holiday cheer. Talk about forward voltage!

We love the concept, and the circuit couldn’t be more simple. A coin cell is released at the top of the tree and rolls down a series of angled foam board railings covered with 1/4″ copper tape. As the coin cell travels, the negative terminal shimmies along the face of the tree, which has corresponding ground rail tapes. There’s no microcontroller here—all that’s needed for blinks are breaks in the negative rail tape.

The challenging part of a project like this is the execution. Getting a coin cell to ride the rails without falling off required angle experimentation prior to and during the build. Now that it’s done, keeping the tree tilted back against the wall is key. [Frank] explored several options for returning the coin cell to the top using a camera motor and the gear assembly from an old inkjet, but for now, his six-year-old does the job without complaint. Check out his work ethic after the break.

9 thoughts on “LED Tree Brings Gravity to Christmas

  1. Ha, fun – I’m imagining one of these as part of one of those machines they have in science museums which lifts up balls on a conveyer belt and drops them through various rube-goldberg-style obstacle courses.

  2. Nice, clean concept. Which gets me thinking the same mechanism can be applied in another way which uses real coin as conductor. The “blackhole” coin donation boxes in Malls are showing their age.

  3. Seems like it would last a little longer if the track shapes were changed a little. You just need a short ramp section followed by a level section, since you don’t need continuous acceleration the whole way.

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