This Cryptic Calendar Displays the Date with Several Mysterious Rings

Drawing Inspiration

For hundreds of years, timekeeping devices have been about more than just the time. They have been a way for tinkerers and craftsmen to showcase what is possible mechanically (and now also electronically). That's why Instructables user Wolfspaw created the Cryptic Auto-Calendar, which has no easily-discernible symbols on the front. It combines the rotational mechanism of this Automated Perpetual Calendar with the style of this Cryptical Calendar into a single project.

Some Important Changes

As previously stated, this calendar blends two distinct projects into one, which required some heavy modifications to work. First, Wolfspaw removed the original text that was on the rings, and replaced it with an inverted font. This font encodes numbers and letters as cryptic blocks of polygons that are revealed once masked off. The characters were placed at the 12 o'clock position and rotated around the center into the correct place. This had the added benefit of being just 75% the size of the original, which meant smaller print times and less material in fabrication. The back of the device was also changed to a completely enclosed housing, which dramatically cleaned up the aesthetics of the piece.

Required Hardware

Hardware for this calendar was surprisingly simple, with a set of three 28BYJ-48 stepper motors and their accompanying ULN2003 drivers being used to rotate the rings. The control board is an Arduino Nano, which uses Hall effect sensors and magnets to determine the home position for each ring, along with an RTC for accurately keeping track of the current date.

There is a plethora of additional nuts and bolts that are used to hold everything together, such as M3 screws for the enclosure and face plate and M5 screws for the ring assemblies.

Fabrication

This automated calendar requires quite a few components to become operational, but thankfully, most can be 3D-printed in a short amount of time. In order to manufacture the rings themselves, each ring was separated into several fragments that fit onto a standard bed. Parts such as the character frames, plates, and supports were fabricated and then sanded until smooth, where they were then placed onto a CNC machined backplate that holds everything in place.

The Rings

This project consists of three rings, with one corresponding to the day of the month, the month, and finally the day of the week. Each ring is composed of the 3D-printed outer gear, which is inlaid on the underside, and the characters on the top, which were carved by a CNC mill. Wolfspaw was able to use a single piece of material for all of the rings.

Wiring

Now that each piece had been created and mounted to the backplate, it was time to work on the electronics side of things. The RTC simply connected to the Nano's I2C pins: A4 (SDA) and A5 (SCL). The stepper motors were a bit more complex because each one requires 4 pins to operate. Lastly, the three Hall effect sensors were connected to three analog pins.

The Code

At the top of the code, several constants are defined. The number of steps per value of each ring is defined, which is determined by multiplying the ratio of ring gear teeth to the number of drive gear teeth by the ratio of steps to each option. As an example, it takes 2048 steps to advance by one day of the week because (56/8)*(2048/7)=2048. Since the rings rotate clockwise, this value becomes negative.

The RTC's current date and time is also set in the code, and its value gets updated whenever a new sketch is uploaded to the Nano. Finally, the rings rotate until each one is aligned with its corresponding Hall effect sensor, which tells the Nano that it's now homed.

Overall, this project looks very interesting due to how the characters aren't visible until views through the mask, and moveable art is always a fun maker topic. The next iteration of this device is sure to mesmerize even more.