When my friend Eric gave me a dive computer case that had a problem, I decided to use it and build a CO2 monitor for a rebreather by making some modifications to the case. A 32bit processor was used in collaboration with the MS5803 depth sensor as well as the SCD41 Co2 sensor. The CO2 sensor is a relatively new infrared sensor from SENSIRION and works with extremely low consumption giving real measurements even in an environment with high humidity by collecting samples every 5-30 sec accordingly. For rebreather use a  humidity collector is also required in order to achieve the maximum possible accuracy. The measurements it takes are transformed into a partial pressure of CO2 at the corresponding depth with the help of the depth sensor and the processor.

 

We notice that on the surface and after calibrating the CO2 sensor it should show 0.4-0.5 because the CO2 levels in the city environment are between 400-500ppm. When connected to the loop we will notice that after a few breaths and as long as the soda filters phave been properly fitted the value should drop to 0.0-0.1. An 84X48 monochrome screen was chosen which had suitable dimensions to fit. The consumption reached 0.1 mA in sleep mode and we can asume that with an LS14500 battery it can last about 8 to 12months. The purpose of  this project is to have an additional indicator and alarm to make our diving even safer. Its use so far seems satisfactory and is still being tested.