Teyleten Robot SCD41 Gas Sensor Module CO2 Carbon Dioxide Temperature and Humidity Gas Sensor Module I2C

This is a good sensor at half the price of the identical unit from other sources. Be careful when establishing the ground. In my test set up I used a separate power source from the Arduino and failed to use a common ground. This cost me two days of debugging until I figured out my mistake. Keep in mind that this Is a precision product. Grounding and shielding will be important if used in a field environment.

This sensor worked well with esphome and reported very plausible values out of the box even with self-calibration disabled. I believe it's a knock-off of the original sensor, but it seems to work well enough. If you have issues with noise, note that these sensors are sensitive to airflow and sound due to how they measure CO2. The sensor should be exposed to open air, but not directly forced airflow.

The CO2 sensor itself seems to work fine using the Adafruit SCD41 example code, and the readings appear to be reasonable, though I don't have a calibrated instrument to compare to. Keep in mind that the design of the instrument means that it isn't suitable for detecting rapid fluctuations, particularly once it has gone high. It will take several minutes for the reading to return to baseline, even with excellent ventilation. This is just a limitation of these MEMS sensors. The temperature and humidity sensor onboard would be a handy addition, but there is a severe calibration issue on the unit I received. Temperature reads nearly 25% low compared to multiple calibrated thermometers. It is measuring absolute humidity correctly, but because of the thermometer error, it calculates humidity as being much too high. As it sits on my desk, actual room temperature is 20°C, and RH is 43% (Dewpoint of 7°C), according to 3 different models of sensors. The SCD41 is reading 16°C, and RH of 60% (It is correctly reading the dewpoint at 7°C still). This error seems to be constant regardless of input voltage. The SCD41 sensor datasheet has a calibration method for the CO2 sensor, but it doesn't appear to support calibration of the temperature sensor. If you want this for a weather station or greenhouse controller, you probably should use this item for CO2 only, and add a BME280 or similar for temperature and humidity measurement.

No more words required, it is a good mix of CO2 ppm, temperature, and humidity. Almost plug and play.

I tried with the Sensirion_I2C_SCD4x and SparkFun_SCD4x_Arduino_Library on an Arduino Nano. Plus Sensirion raspberry-pi-i2c-scd4x on a raspberry pi. In all cases , it can return the serial number but never returns any information requesting measurement or other settings commands. Just hangs. My guess this is bad manufacturing run that might have some good ones that are being unloaded. I expect that on Aliexpress not on Amazon. Expense way for Beta testing.

Other sensors with this chip (SCD41) cost almost twice what this one cost. It seems to work just fine.

I don't know how to rate this one. It is a sensor that is finicky for the solution I'm attempting to use. I paired it with an ESP32 and another sensor (PMS5003 Air Quality Sensor) which is working fine. The SCD41 didn't want to work and gave me several unknown errors. Searching online and Google and AI tells me that the power seems to be the issue so I've currently got a capacitor on order to see if I can rectify the power issues and get this sensor working but seemingly it is much more finicky that the other temp/humidity sensors I've used previously. I will also say, I'm a tinkerer so this could all be my fault so I will take some accountability and warn that this could be a me problem. Device was packaged well and was delivered on time, and was priced right for the product so take it with a grain of salt.

I'm running Tasmota on an ESP32 with a 4000mAh battery and OLED display. Totally easy to use, just plug it in. Uses I2C, Tasmota sees it without any configuring.