Open-Source Microcontrollers for Science - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 66

The Polar Bear humidifier, which is used to increase the humidity when it is below the hu-
midity set point.
The refrigerator, which is used to cool the chamber when it is above the temperature set
point.
The fan, which is used to blow humid air over the passive dehumidifier when the chamber
humidity is above the humidity set point.
4.5.3 Wiring diagrams
For experienced electrical engineers, the wiring and circuits in the Polar Bear Open-source En-
vironmental Chamber are prety simple; however, to most researchers, the inside of the in-
ished product is going to look like a bowl of spagheti. To cut through the complexity and
make it easy for everyone, the wiring diagram is described below and shown separately for
each of the eight subsystems that make up the Polar Bear. Wiring each subsystem is fairly
straightforward. As you get near the end, simply ignore what is going on in your bowl of spa-
gheti wires and just make sure the circuit you are constructing matches the wiring diagram
for the subsystem.
The wiring diagram for the LCD display to the Arduino is shown in Figure 4.5 and needs
the Arduino, potentiometer, and the LCD display along with connection wires.
FIGURE 4.5 Wiring diagram for the LCD display to the Arduino.
The following nine connections should be made as seen schematically in Figure 4.5 :
1. Gnd → Potentiometer—Arduino Ground
2. V cc → Potentiometer—Arduino 5 V
3. V o → Potentiometer sliding contact