CO2 Engine (K33) BLG CO2-Sensor always sends the same value

Other Hardware Sensors
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CO2 Engine (K33) BLG CO2-Sensor always sends the same (mainly) implausible measurement value and does not change values when in contact with breathing air.

For my setup I followed the following instructable for the K30: https://www.instructables.com/Track-CO2-Carbon-Dioxide-Levels-With-Ardunio-and-C/.

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I just took a BLG K33 CO2 sensor instead of K30 and an Arduino Nano instead of an Arduino Uno.
I also took the code from the referenced website and could establish a connection.

At the moment I constantly get 89 ppm for CO2 concentration. It also used to be 702 or 99 or 146. All these values are neither plausible nor do they change when exposed to breath. The change in value is arbitrary but mostly happens after switching the sensor off and on again or when I moved the setup.

Did anybody else encounter this problem? I am grateful for your help.

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The K33 is not a direct replacement of the K30. According to the datasheet it's digital signal voltage is 3.3V and any signal on these pins must be below 3.8V. As you connected the Nano (5V) directly you might have fried those pins. You need a level converter to connect this sensor to the Nano.

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Thank you pylon. I now installed a voltage divider but values keep staying the same. Indeed, the pins are fried. This was an expensive experiment.

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