I decided to configre an ESP32 as an air quality monitoring device.
So i hooked up an SDS011 particulate sensor (every 5 minutes) and a senseair S8 (LP) CO2 sensor (every minute) over UART. Both sensors show up and report data. All seems well. Then when i wanted to do a manual calibration of the senseair S8 i noticed that the data looks strange. There seems to be a spike in CO2 levels spot-on every 5 minutes.
This seemed too artifical to be true. And then i realized the SDS011 measures every 5 minutes. I disconnected the air-refreshment fan of the SDS011 (Which spins up for every measurement), and low and behold the 5 minute spike is gone.
It is clear that the activation of the fan of the particulate sensor is causing abberant readings from the CO2 sensor.
At first i was running the ESP32 from a Li-ion USB powerbank. So i figured perhaps the power draw of the ESP + the two sensors may cause a voltage drop or EMF or something, throwing the CO2 sensor readings off. So i proceeded to put a fat electrolytic capacitor (2200uF) between 5V and ground. Unfortunately, this didnt seem to help.
Does anybody have any other suggestions to avoid this issue?
The 5 minute spike is clearly visible in the red squared area.