Making CO₂ Sensors Fail Visibly, Not Silently
William Collis has created a CO₂ monitoring system that is built to fail visibly, ensuring that a malfunction is never silent.
William Collis noticed a critical flaw in his home CO₂ monitoring setup: the system always displayed the last known-good sensor reading.
A flat, unchanging number can be exactly what a dead sensor looks like, making it impossible to tell if the reading is accurate or if the device has failed.
To solve this, he modified the system so that a faulty sensor is not hidden behind apparently-good values, and the device itself flashes a visible fault LED in the case of a problem.
Hardware and Software
Each monitor in his setup is a Sensirion SCD30 CO₂ sensor, paired with a Seeed XIAO ESP32-C3 running ESPHome to communicate with Home Assistant.
The modifications were made within a configuration file and did not require rewriting the ESPHome firmware.
This approach ensures that the system is more reliable, as users can immediately see when a sensor is no longer functioning correctly.
Next Steps
Collis suggests that if a home automation system needs more ruggedizing, a homebrewed UPS for Home Assistant could be a useful addition.
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