Making a Snow Globe That Generates Its Own Snow
By combining a vapor chamber with a cooler, Sean Hodgins has made a snow globe that is closer to its namesake which produces actual snow.
'Tis the season for decorations
The holidays are full of decorations such as wreaths, trees, ornaments, and stockings, but nothing quite captures the season like a snow globe. Nearly all if them feature a small figuring encased in a fluid-filled glass chamber that, when shaken, causes tiny flakes of white plastic to begin floating and then sink, thus mimicking snowfall. Sean Hodgins had the idea to make his own snow globe, but rather than using artificial plastic pieces, he wanted it to produce its own, real snow.
Generating the cold
Fitting an AC unit or freezer into such a small space was unfeasible, so Hodgins had to turn to something more compact. As you might have heard mentioned elsewhere, there exists a class of thermal pumps that make use of the Peltier effect to move heat across a gradient and create a larger temperature difference on its two sides. In short, a thermoelectric cooler has two sides, with one touching the object being cooled and the other with a heat exchanger. When current flows through the device, the cooling side drops its temperature while raising the other side's temperature.
A basic design
In order to get ice crystals to form within a glass chamber, Hodgins milled a simple snowman shape out of metal on his lathe and then added a small 3D-printed hat and scarf to complete the look. From there, he stacked three Peltier coolers to compound their chilling effect that can drop the cooler side below freezing in room temperature. At the other end is a PC CPU fan cooler, which exhausts the heat away from the globe. Finally, he used a cheap ATX power supply to provide enough current for the Peltier and fan.
Building the chamber
The globe portion of the snow globe was fashioned from a simple, hollow glass sphere that had an opening at the bottom. Hodgins also attached a disc containing a pair of 2W resistors that sits around the snowman and creates enough heat to vaporize any liquid within the chamber for creating condensate later. Finally, this whole piece was placed on top of a custom acrylic case, which houses the heatsink, fan, and power supply.
Waiting for part two
As seen in Hodgins' video, the snowman quickly collects ice crystals on its surface when power is applied, but he has plans for a more advanced use case: generating clouds of isopropyl alcohol vapor and using it as a radiation meter. To view that part in action, you'll have to wait for part two of this project.