One ring to rule them all, one ring to tell time!
Watches come in all shapes and sizes, but this DIY ring watch featuring the ATtiny85 is quite a feat of miniaturization! It’s based on two previous posts by Maker Chen Liang, explaining how the watch guts work on a breadboard and how he put a similar design together in a more traditional wrist watch. As he had to use a smaller battery than the breadboard version in his ring, he expects battery life to be around half a year.
The ring’s ATtiny85 was programmed using a Digispark (as outlined here), and the device’s circuit was set up on three tiny boards for physical flexibility. The circuit board sections included one for the chip, another for the display, and another for three tightly-spaced buttons. These buttons were able to share one analog input pin on the tinyAVR MCU by using a clever technique involving resistors across two of the button circuits. The three buttons were wired into an analog input, giving different voltage reading depending on the button pushed. Since the ATtiny85 could differentiate between these readings, only one pin was needed for control.
The watch band was 3D-printed, and covered with a clear thermoplastic layer. Although impressive by itself, Liang has plans to “research sync time method, GPS, Wi-Fi + Internet, BLE + mobile phone, and more.” Maybe we’ll see this project expand to a variety of rings that can be worn and linked via Bluetooth depending on what is needed in a particular situation. Do we sense a Kickstarter? In the meantime, check out the Maker’s entire build here.