If you want to display static text, a simple sign will do nicely. If you want to display dynamic text, LED or LCD displays will get the job done. But, there is definitely a precedent for all kinds of electro-mechanical displays, which used to be far more common before digital displays became affordable. A simple split-flap display, for example, used to be a practical solution. And, while it may not be practical, this scrolling bubble display is far more interesting than a boring old LED sign.
This tutorial was created by Simon Jelley and Mark Mellors of jellyandmarshmallows.co.uk, and it may just be the most unique way to display text that we’ve ever seen. The display is made from twin-wall polycarbonate plastic roofing sheet, which has enclosed channels running down it’s length. Those channels are filled with water, and the entire contraption sits at roughly a 30° angle. When air is injected into those channels air bubbles are formed and float to the top. By coordinating those air bubbles, text can be displayed!
The air comes from a compressor for an airbrush, and bubbles are released by solenoid valves. Those solenoids are controlled by an Arduino, which takes in text via the serial connection and converts it into bubble sequences. Obviously this isn’t perfect, mostly because it’s difficult to account for the slight variations in bubble travel speed. But, it can produce readable text and, more importantly, looks cool.