Building an Ingenious Perpetual Clock Called Cyclotron
Brett Oliver was inspired after he saw an antique perpetual flip calendar and so he applied the same mechanism to his Cyclotron clock.
It is easy for us to rely on digital electronics to solve our problems today. If you asked a modern engineering team to design the very first light switch, you can bet that the final product would contain a microcontroller. But engineers working before the digital age didn’t have that luxury and necessity forced them to come up with some very clever electromechanical solutions. Perpetual flip calendars, patented in 1929, are great examples of that. Brett Oliver was inspired after he saw one of those perpetual flip calendars and so he applied the same mechanism to his Cyclotron clock.
The original perpetual flip calendar was purely mechanical. It resembled a domino attached to a pivot mount on a heavy base. A small window on each side of the “domino” displays the day of the month. To change to the next day, the user only needs to flip the domino upside down. It’s difficult to understand the mechanism by looking at it from the outside, but it is actually very simple. A bunch of cards with numbers on both sides sit inside of the domino. The act of flipping the domino causes the cards to slide down and then back around, so that the mechanism rotates through each card. The video below from Measured Workshop demonstrates the mechanism at about 5:30.
Oliver’s Cyclotron uses a similar mechanism for each of the four digits of his clock. The first digit only needs two numbers (0 and 1), the second digit needs the full ten numbers, the third digit only needs 0-6, and final fourth digit needs the full ten again. The number cards in each mechanism, along with the mechanism cases, were all 3D-printed. Each digit has its own 28BYJ-48 pancake-style stepper motor to flip the mechanism. An Espressif ESP32-WROOM development board controls the stepper motors through stepper driver boards.
An RTC (real-time clock) connected to the ESP32 keeps track of the exact time so that the digit flips occur at the appropriate intervals, but Oliver did integrate a control interface to set the initial time. That takes into account the current position of each digit and the number of rotations required to reach the required number card. The control interface also has provisions for daylight savings time.
The Cyclotron looks fantastic with its beautiful wood base, black frame, and clear Perspex dust cover. If you want to build your own, Oliver posted detailed instructions and all of the files you need to get started.