Temperature Sensor

Syrus can communicate with compatible 1-wire digital thermometers that use a chip called: DS18B20. The DS18B20 is capable of communicating in two modes, a normal power mode and a parasite mode which derives power from the data line, eliminating the need for an external power supply.

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Warning when purchasing DS18B20 sensors

When purchasing these sensors be sure to read the reviews as there are a lot of sensors that may advertise DS18B20, but they don't actually use the chip and you're not able to read the temperature data from them.

Example of one that works:

Look for sensors that say they work in parasitic power mode, which means they use the correct DS18B20 chip. Link to purchase.

For any 1-wire accessories such as temperature and ibutton sensors, up to 64 total sensors can be supported simultaneously. This means if you want to read an ibutton you can have a maximum 63 other temperature sensors connected all reading temperatures at the same time. Note that this does not affect the authorized/whitelisted list of ibuttons, up to 500 ibuttons or 1-wire accessories can be authorized for use with the apx-onewire tool.

General Overview

• The way it works is that you connect one or several temperature sensors in normal or parasite mode to Syrus
• You read the temperatures with the apx-onewire temperature getall command
• Give your temperature sensors aliases and install them

Installation

Syrus 4 Datasheet with Pinout

1-wire Wiring Pinout (found in 14-pin molex)

Parasite mode

Configuration

Once you have the temperature sensors connected, you can use the apx-onewire to read temperature

$ sudo apx-onewire temperature get_all

{
    "temperatures": [
        {
            "alias": "tempsen1",
            "id": "8D01144D07DBAA28",
            "value": 22.625,
            "connected": true,
            "epoch": 1608047806
        },
        {
            "alias": null,
            "id": "3C12345D07DBAB29",
            "value": 22.437,
            "connected": true,
            "epoch": 1608047807
        }
    ]
}

Afterwards you can set an alias and proceed to install on a real life scenario.

Redis Interaction

To notify changes on a temperature sensor, the onewire application publishes:

onewire/notification/temperature/state onewire_temp_json_object

"PUBLISH" "onewire/notification/temperature/state" "{\"alias\":null,\"id\":\"8D01144D07DBAA28\",\"value\":27.437,\"connected\":true,\"epoch\":1610658389}"

Tips

The ID of the 1-wire sensors is not printed on the temperature sensor, so you'll have to connect one at a time and use the get_all command to read the values, then assign an alias to each sensor.