EMG is something we started from a few years ago, and it's a relatively simple signal you can measure easily - even using an ECG device with a different algo. But we ended up using several uECGs, which looked cool, but was very bulky - so we made uEMG to streamline it a bit
Early prototypes looked more or less like our Skulljack project (a contactless EEG device) - even the hexagon shape was the same! uEMG had only four channels though, and worked with wet electrodes. We planned to showcase it at MakerFaire Rome in 2019, but couldn't make it work as intended, shelved the project, and then COVID and survival mode happened. But the idea stayed with us and we managed to revive the project in early 2021.
First, we ditched the hexagon shape for a more fashionable bullet type. The four channels stayed, but instead of wet electrodes and wires we designed a custom bracelet with conductive fabric, worn on the arm, to measure and receive the signal. This required several design iterations, a lot of research into which muscles do what, actually mapping the muscles on the arm, a lot of brainstorming how the design would be worn and how it will be used, and a lot of time and effort finding a seamstress who would make our bracelet design into an actual bracelet. But as of October 2021, we think we finally have something we can use (it just needs some more changes - it's a process!).
Hardware-wise, the device is based around an MCP3912 and an AD8608 opamp for analog signal measurement, and an nRF52832 SoC for signal processing, RF and Bluetooth. This is a similar setup to uECG, only with more channels! The current version also switched to an IPEX2 antenna for better signal quality. On the analog side of things, five button connectors (four channels and one for the ground) hold the device in place and connect to conductive fabric pads using conductive thread.
All project files can be found on github: https://github.com/ultimaterobotics/uEMG