Open-Source Microcontrollers for Science - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 71

can normally find manuals for relatively recent appliances on line. If it is an older salvaged
refrigerator, you may need to contact the manufacturer to get it. Once you have their diagram,
detach their thermostat and connect the main protection wires to the Normally Opened Pin 29 on
the relay as shown in Figure 4.13 . Connect the Relay to Arduino Digital Pin 22 . In this way you
are essentially controlling a relay with the Arduino that controls the Coolers main relay. Then
plug the refrigerator or cooler as you would normally into an AC wall outlet when you are
ready to proceed.
FIGURE 4.13 Wiring diagram for the refrigerator/cooler.
It is always useful to have a wiring organization. To do so, as you build the system, think
carefully about soldering boards, the use of zip ties, and apply your creativity. Sometimes it is
also helpful—particularly for wire runs—to dry run them first before making final length and
soldering decisions.
4.5.4 Construction of the Bear Chamber
The construction of the Bear Chamber is relatively simple even if the untidy state of a nonen-
closed system is a mess of wires in their “naked” state as seen in Figure 4.14 . 30 The key step is
to ind the correct wires for the cooler protection relay atached to the thermostat, remove the
thermostat and connect the wires to the Arduino relay as instructed above.