When you think of slow and semi-permanent display methods, E-Ink may come to mind, as once the proper bits are turned on or off they require no power to operate. On the other hand, a “no-power” display technology has actually been around since the 1960s in the form of flip-disk, or flip-dot, displays. They use an array of disks, each containing an electromagnet setup that literally flips the dots between a visible or a dark position.
Though they are gradually being replaced by newer technologies, this type of tech could be seen on public information displays, such as busses or airports for many years. Naturally, whenever a technology starts to phase out, enterprising hackers swoop in and re-purpose it for our own means. For better or worse, much of the time this turns into some sort of clock, like “Dottie,” seen on Hackaday.
As interesting as that is, it still looks like quite a bit of work. If you’d like a head start on your clicky clock, Shmonogear is selling a Bluetooth-enabled flip-clock prototype. It shows the hours, then a colon, then the minutes, pausing in between for a set time. Interface requires you to send it commands via the Nordic Bluetooth toolbox app, meaning you’ll need some technical expertise to work with it.
Naturally, this clock isn’t recommended for quiet areas due to its intermittent clicking, but would be great for somewhere that needs a little ambient noise!