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Temperature Sensors

We are using DS18B20 digital temperature senors. These are connect to the 1-wire-bus from the RaspberryPI (gpio4). (HAT fixed Pull-Up 10k, Relayboard Pull-Up potentiometer)

Schematic

see relayboard schematic

Node-Red Node

In Node-Red we installed a custome node 'node-red-contrib-ds18b20-sensor' to interact with the sensors. Check the temperature DS18B20 flow for details. The sensors are read every 30s and this node gives us an array of all detected sensors. Values are stored in the global variables 'Temp1' to 'Temp4'. If u using other sensors or get the data from other places/devices, simply write your data to these global variables and it will show up in the frontend.

Set Names

To differentiate the Sensors we implemented a function "get temp sensors". If this is actived the sensor values are checked every second for 1m. Now you can change the temperature on a specific sensor to locate them. After finding the right sensor you can type set its name to your likings.

HeaterSensor

You can define an inside temperature sensor (1-4) to set a specific sensor as a reference for the heater control. This sensor is stored in the global variable 'heattempsensor'.

Hardware

We are using a 10k pullup resistor on the RPI hat and a 0-10k potentiometer on the relayboard. Normally, with the 10k, we can catch four sensors without any problem. If you're using more sensors or long wires you can change the resistance on the relayboard with the potentiometer. This can help you to catch all sensors.

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