Clarus is a DIY, all-day air purifier built around a Seeed XIAO ESP32-S3, designed for cheap, quiet, low-speed continuous filtering.
Why I made it
Most consumer air purifiers are either overpriced, ugly, or engineered for peak CFM numbers nobody needs. I wanted something that runs quietly in the background all day at a modest air-exchange rate, looks like it belongs on a shelf instead of a data center, and costs a fraction of retail because I built the electronics myself. The design philosophy: cheap, quiet, and slow beats loud and maximal. Two stacked 120mm PC fans pulling air through a Levoit Core-style HEPA+carbon cartridge at low speed will keep an 11×11×11 ft room at 2–3 ACH without anyone noticing it's running.
How it works
Clarus is split into three independent pieces, each solving a different problem:
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Purifier Controller (main board) A Seeed XIAO ESP32-S3 lives on/near the purifier enclosure and handles the actual fan control:
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Environment Monitor (external addon) A standalone ESP32 sensor board, based on a modified Dynix7 Environment-Monitor schematic, sits out in the room rather than inside the purifier because ambient readings are more accurate away from the unit's own airflow. It reads:
Temperature/humidity (AHT20) TVOC/air quality (AGS10) Secondary temperature (TMP102) Particulate/dust density (GP2Y1010AU0F, with a discrete NPN driver circuit)
It's USB-C powered only the battery charging block, light sensor, and pressure sensor from the original Dynix7 design were stripped out since they weren't needed here. 3. Bluetooth Companion App (addon) A phone app for remote monitoring and manual override, connecting over BLE. This is intentionally the least essential piece Clarus is designed to run correctly with the app closed or uninstalled.
Control hierarchy Clarus doesn't need a phone to function. Priority order, highest to lowest:
Potentiometer / physical override — always wins Device-to-device BLE auto mode — the Environment Monitor broadcasts air quality as a BLE advertisement packet; the Controller scans and adjusts fan speed autonomously, no app required Phone app override — manual control when you want it Fallback — holds the last known value for ~10 minutes, then drops to a time-based schedule if nothing's been heard