Kombucha! It’s a delicious fermented beverage that is kind to your digestive system and often sold in glass bottles. You don’t just have to use those bottles for healthy drinks, though. As [Simranjit Singh] demonstrates, you can also use them to create your very own plasma tube.

[Simranjit’s] build begins with a nice large 1.4-liter kombucha bottle from the Synergy brand. To make the plasma tube nicely symmetrical, the bottle had its original spout cut off cleanly with a hot wire, with the end then sealed with a glass cap. Electrodes were installed in each end of the tube by carefully drilling out the glass and installing small bolts. They were sealed in place with epoxy laced with aluminium oxide in order to improve the dielectric strength and aid the performance of the chamber. A vacuum chamber was then used to evacuate air from inside the chamber. Once built, [Simranjit] tested the bottle with high voltage supplied from a flyback transformer, with long purple arcs flowing freely through the chamber.

A plasma tube may not be particularly useful beyond educational purposes, but it does look very cool. We do enjoy a nice high-voltage project around these parts, after all.

If you think shorting a transformer’s winding means big sparks and fried wires: think again. In this educational video, titled The Magnetic Bypass, [Sam Ben-Yaakov] flips this assumption. By cleverly tweaking a reluctance-based magnetic circuit, this hack channels flux in a way that breaks the usual rules. Using a simple free leg and a switched winding, the setup ensures that shorting the output doesn’t spike the current. For anyone who is obsessed with magnetic circuits or who just loves unexpected engineering quirks, this one is worth a closer look.

So, what’s going on under the hood? The trick lies in flux redistribution. In a typical transformer, shorting an auxiliary winding invites a surge of current. Here, most of the flux detours through a lower-reluctance path: the magnetic bypass. This reduces flux in the auxiliary leg, leaving voltage and current surprisingly low. [Sam]’s simulations in LTspice back it up: 10 V in yields a modest 6 mV out when shorted. It’s like telling flux where to go, but without complex electronics. It is a potential stepping stone for safer high-voltage applications, thanks to its inherent current-limiting nature.

The original video walks through the theory, circuit equivalences, and LTspice tests. Enjoy!