The DigiDisk Clock Merges Analog and Digital
This unique clock built by potblitd that merges analog and digital characteristics into a single device.
We all tend to think of clocks as either analog or digital. Analog clocks are circles with hands, while digital clocks display illuminated numeric characters. But if we stick to objective definitions, the distinction gets murky. If an “analog” clock keeps track of time with a microcontroller and sets the hand positions with stepper motors, is it really analog? What if a digital clock displays numeric characters on physical dials? The DigiDisk is a unique clock built by potblitd that merges analog and digital characteristics to explore those ideas.
If you only glanced at DigiDisk for a split second, you’d probably think it was a digital clock. It displays four digits of numeric characters like a typical digital clock. And like most digital clocks, those numeric characters are made of combinations of seven segments that are either “on” or “off.”
But the segments aren’t LEDs — they’re white lines painted on black discs. Thanks to a clever arrangement and a faceplate that masks most of the disks, the discs can rotate to show one segment, two segments, or none at all. The effect looks digital, but is actually analog in the same way as a clock’s hands.
And the ambiguity doesn’t stop there, because the timekeeping is entirely digital. A Microchip ATtiny402 microcontroller keeps track of the time through a PCF8563 RTC in exactly the same way as almost every digital clock on the market. It then rotates the discs as necessary using 16 MG90S servo motors (one for each disc). That isn’t an analog clock motion, because the discs don’t rotate at a constant rate. The microcontroller sets their angles as necessary, which depends on creating the correct numeric character for the current number.
To simplify assembly, potblitd designed a custom PCB for the electronic components that also has mounting holes for the servo motors. The discs are also PCBs that are very thin and have their white lines drawn as silkscreens. The front plate is a sheet of rigid PVC attached with spacers. This is a clever construction method for a clever clock.
This clock design may not appeal to everyone, but it will certainly give the pedantic and nerdy among us something to think about when they consider the distinction between analog and digital.