Build a Digital Watch in an Analog Case with Programming Crown

Software engineer Joe Sullivan set out to build a watch with a digital display in an analog case, but instead of using traditional buttons to set the time, he wanted to use the case’s rotating crown. Easier said than done, as he managed to complete his device, there was more involved with the project than he expected. Sullivan started a development process to get a better understanding of how a digital watch could set the time using a rotary crown, which he did by using an Arduino Uno, a 4-digit LED display, and an encoder.

While he technically created a clock with the hardware, it wasn’t very accurate, and it consume a lot of power, so he decided to bypass the Arduino in favor of a Microchip Curiosity 8-bit development board and programmed it using the MPLAB X IDE. He also switched out the LED display for a smaller quartz crystal version. At this point, Sullivan designed a PIC16LF1936-equipped PCB small enough to fit inside of a watch face based on the last successful clock revision he made during the development process, along with a 40mAh battery that allows the watch to run for least a half of a year.

After assembling all the hardware he needed, Sullivan succeeded in assembling his digital watch that can be programmed using the rotary crown, which was done by attaching a small magnetic rotation sensor to the PCB and a magnet to the crown stem. As the sensor requires power to function, Sullivan incorporated a reed switch to the PCB that closes when the crown is extended, which then activates the sensor.

A complete walkthrough can be found in his blog post for those who would like to recreate his digital timepiece.