Pandemic Project #1: Wireless sensors and gateway for CareBank
The Covid-19 pandemic was devastating to public health, but it also stimulated the development of new technologies hoping to re-establish our social connections. I met Claude Goodman in March 2020, learned of his CareBank project, and gladly took on the challenge of developing improved wireless sensors for that system.
The concept of a Bluetooth Low Energy module and motion sensor was not unusual, but long-range transmission, long battery life, and ease of battery replacement by an elder were more demanding requirements. We used BLE 5.1 and careful antenna design to extend the range and a low data rate to achieve >1yr of battery life. To change the battery, the user just slips off a silicone band (blue band in the rendering) and slides a new coin cell battery into a slot.
The next challenge was reliably relaying the sensor data to the CareBank servers in the cloud. While an up-to-date smartphone with an Internet data connection could do that job, it wasn’t realistic to assume every elder had such a smartphone always operational. As an alternative, I developed a Bluetooth-5-to-cellular gateway prototype. To maximize range, antenna placement was carefully optimized, and the communication link uses positive acknowledgement and retransmission to overcome dropouts. The gateway’s 3D-printed enclosure plugs into a standard USB charging brick, and the combination plugs into a wall outlet like a nightlight.
When it was time to manufacture a prototype run of 75 sensors, we hit one more challenge: the 2021 global semiconductor shortage. I learned how to source components from dwindling stocks in multiple countries and have the PCBs fabricated and assembled overseas. We were lucky; some key chips now have a one year lead time.