This Digital Clock Doesn’t Need LEDs, Because It Has Water

The first timekeeping devices were probably just sundials, in the form of a stick jabbed into the dirt. But the first timekeeping devices to work independently of the sun were likely water clocks, which used the flow of water under gravity to track the passage of time. They were elegant and simple. But Strange Inventions might have misunderstood the assignment when he built his water clock.

Terminology jokes aside, this is a clever project. It is like a digital clock, but with little bottles of water instead of LEDs. It is, however, orders of magnitude more complex than an ancient Babylonian water clock.

The clock has four “digits” and each of those has 15 “pixels” in a 3×5 grid, which is the lowest effective resolution you can use and still get recognizable alphanumeric characters. Strange Inventions needed a way to turn each bottle “on” and “off.” With the water dyed a bright blue, a bottle is “on” when full and “off” when empty.

But how to get water into and out of each bottle?

Strange Inventions originally planned to use a single peristaltic pump to push water from a reservoir through a divider, valves, and nozzles into the bottles. He also wanted the same to work in reverse to suck water out of the bottles. Solenoid valves would let him control which bottles to target.

That idea unfortunately failed. There were constant leaks, issues with air in the lines, and problems with differing pressure affecting flow rates from one bottle to the next. It was a disaster.

After a great deal of troubleshooting and experimentation, Strange Inventions settled on far more reliable system. It has a tiny membrane pump dedicated to each bottle and water only flows in one direction: into the bottle. When it is time to “refresh” the clock, a servo-driven mechanism behind each digit tips all of the bottles and dumps their contents into the basin below, which is also the reservoir for filling the bottles.

The result looks pretty incredible and certainly beats the water clocks made 3,500 years ago.