Temperature controller module in reef-pi does not require power controller features, i.e. users can use reef-pi to just monitor and log temperature, but for turning on/off heater or chiller requires power controller module. In this guide, we'll be extending the power controller.
We'll use submersible DS18B20 temperature sensors for monitoring temperature. The DS18b20 requires minimal circuit (only a single 4.7K resistor) for integration with Raspberry Pi. We'll use the existing PermaProto HAT for this. A DS18B20 sensor will be connected to the controller enclosure using a 3.5 mm audio jack. The probe itself will have a 3.5 mm male audio connector, and the controller enclosure will have a panel mount female audio jack connector.
Note: Due to our choice of 3.5 mm audio connector, we should always avoid plugging/unplugging the temperature sensor when reef-pi is running. Always power down reef-pi before connecting or disconnecting the sensor. The 3.5 mm audio jack causes +Ve and GND pins to be touched (shorted) every time the male connector is plugged in, causing the Raspberry Pi to reboot (which we do not want to happen).
reef-pi supports multiple DS18B20 sensors. It is common to use two or three of these for redundancy. I have tested with up to 7 sensors.