Open-Source Microcontrollers for Science - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 77

FIGURE 4.20 Operating relative humidity range of Bear Chamber.
If dehumidification is necessary, the fan will be activated. Once the fan is activated, the air
will be forced to circulate to the botom of the chamber where the dehumidiiers will dry the
air. The dehumidification process is the slowest of the control processes. This must be factored
into experiments, especially when lower values are set. When the relative humidity reaches
a satisfactory range, it will be kept by activating the humidifier or the fan just when neces-
sary, again contributing to good energy management. A satisfactory relative range is from 3%
below to 3% above the desired relative humidity (set point); in another words, if the desired
relative humidity is H, the range is [H − 3%; H + 3%].
4.5.7 Operation of the Bear Chamber
The operation of the Bear Chamber is easy and straightforward. When the system is turned
on, the main screen will appear as shown in Figure 4.21 .
FIGURE 4.21 Main screen of Polar Bear open-source environmental chamber.
The main screen will show the temperature in degree Celsius, relative humidity in percent-
age and controller status. The possible commands are further information by pressing “ ∗ ” on
the keypad or controller menu by pressing “#” on the keypad.
The further information menu “ ∗ ” will show the temperature and relative humidity set
points (desired values) defined by the user (by default, temperature is set to 25 °C and relative
humidity to 50%) as seen in Figure 4.22 .
FIGURE 4.22 Temperature set point screen under further information.