The Design and Fabrication of a Custom Environmental Control Chamber

This work outlines the design and fabrication of an environmental test chamber with precise and reliable temperature and humidity control allowing for the characterization of adsorption and desorption performance under well-defined environmental conditions. This chamber serves a critical role by allowing for direct comparison between candidate materials across a broad range of temperatures and relative humidity (RH). To achieve this, we built a low-cost custom environmental control chamber that allows for the control of temperature and RH. Our system is controlled with the Arduino Nano microcontroller, and all custom electronics are integrated on a perforated circuit board. We use two AM2315C humidity and temperature sensors that were oriented in opposing corners of the setup. The sensors provide an accuracy of +/- .3°C and +/- 2% RH. For temperature control, we utilized four 110°C Positive Temperature Coefficient (PTC) heaters connected to a solid-state relay and a time-proportional PID (proportional-integral-derivative) control scheme. For humidity control, we connected a central compressed air line regulated to 1 bar, which was split into two lines, one connected to a desiccant air dryer and the other to a bubbler to obtain humid and dry air lines. Two stepper motor-controlled needle valves regulated the flow of each line into the chamber. The two motors were controlled with a PID control scheme to achieve humidity regulation in the range of 20% to 70% relative humidity in our chamber. To minimize thermal gradients within the chamber, we employed active air mixing in the chamber through the implementation of small fans. We were able to maintain a temperature steady state in the chamber to within +/- .5°C of setpoint temperature and +/- 2% relative humidity.