one year working Nova Fitness SDS011 sensor with a rusty metal cover
desolder the + and - terminals for the diode on the top right corner
remove screws showing the photocell (rectangular on the right)
close on the photocell. The cell is connected to the circuit board on the back. On the right showing the terminal for the laser diode.
remove the fan from the top cover. Look pretty clean inside.
looking for accumulated dust but did not found much
found dust on the baffle where the air is coming in and on the wall before pulling out by the fan
close on the where the dust was accumulated
This is where the magic started to happen. The laser diode pulses light across the airflow path and somehow, PM2.5 concentration is estimated by a photocell placing on the ceiling
remove the metal cover and looking for the brain of the sensor
STMicroelectronics NUCLEO-F031K6 chip
Under the cover with the main IC, and TI 77 as the op-amp