Light control

There are different ways to set up a light. This example is based on setting a light with Hermes and Zigbee2MQTT protocol. To start with Node Red setting, your device should be connected to Zigbee2MQTT broker. Have a look on Zigbee2MQTT to see how you can connect your devices.

Used nodes

We used 4 different nodes in this flow. I explain them from the left to the right.

MQTT IN nodes

This is a Node to subscribe a MQTT topic. These nodes subscribe to the four intents we want to use to control the light. They connect to the local MQTT server on the Raspberry Pi (127.0.0.1:1883) and subscribes to their topic. When a topic enters the MQTT server ont data send with the topic is placed into msg.payload.

Function

A Function Nodes are used to run javascript(JS) code. This JS code usually processes the payload of the message enters this node. Here we used two function nodes in a row.

Switch-Case-Slots function

This function saves all slots, handed over by Snips-NLU, in a single message from this command:

var message = {
    cmd: "",
    name: "",
    state: "",
    brightness: "",
    color: "",
    temperature: ""
};

Here is the full code:

var message = {
    cmd: "",
    name: "",
    state: "",
    brightness: "",
    color: "",
    temperature: ""
};

for (var i = 0; i < msg.payload.slots.length; i++) {
        switch(msg.payload.slots[i].slotName) {
            case "cmd":
                message.cmd = msg.payload.slots[i].value.value;
            break;
            case "name":
                message.name = msg.payload.slots[i].value.value;
            break;
            case "state":
                message.state = msg.payload.slots[i].value.value;
            break;
            case "brightness":
                message.brightness = msg.payload.slots[i].value.value;
            break;
                case "color":
                message.color = msg.payload.slots[i].value.value;
            break;
                case "temperature":
                message.temperature = msg.payload.slots[i].value.value;
            break;
            default:
    }
}

return message;

Transform input function

This function transforms the message from Switch-Case-Slots function in a format Zigbee2MQTT needs it. The actual message for Zigbee2MQTT will be placed into msg.payload. The description is shown later on this page.

Here is the full code:

if (msg.state) {
    if (msg.state.toString() === "ein" | msg.state.toString() === "an") {
        msg.payload = {
            state: "ON"
        }
    } else if (msg.state.toString() === "aus") {
        msg.payload = {
            state: "OFF"
        }
    }
    return msg;   
}


if (msg.brightness) {
    msg.payload = {
        brightness: msg.brightness / 100 * 255
    }
    return msg;
}
    
if (msg.temperature) {
    switch(msg.temperature) {
        case "warmweiß":
            msg.payload = {
                color_temp: 400
            }
        break;  
        case "kaltweiß":
            msg.payload = {
                color_temp: 50
            }
        break;
        default:
    }
    return msg;    
}

if (msg.color) {
    switch(msg.color) {
    case "blau":
        msg.payload = {
            color: {
                hex: "0x0000FF"    
            }
        }
    break;  
    
    case "rot":
        msg.payload = {
            color: {
                hex: "0xFF0000"    
            }
        }
    break;
    
    case "gelb":
        msg.payload = {
            color: {
                hex: "0xFFFF00"    
            }
        }
    break;
    
    case "grün":
        msg.payload = {
            color: {
                hex: "0x008000"    
            }
        }
    break;
    
    case "lila":
        msg.payload = {
            color: {
                hex: "0x800080"    
            }
        }
    break;
    
    case "weiß":
        msg.payload = {
            color: {
                hex: "0xFFFFFF"    
            }
        }
    break;
    default:
    }
return msg;
}

Switch device node

This is a simple switch node, it routes the messages to the intend MQTT OUT for the zigbee devices So if the variable msg.name in the message is equal “licht” the message will be routed to the upper MQTT OUT node. This will be also done for the other names defined in there. This is the configuration of the switch node:

"licht" => Output 1
"garagenlicht" => Output 2
"stehlampe" => Output 3
"alle lampen" => Output 4

MQTT OUT

This node publishes the msg.payload to the local MQTT server(127.0.0.1:1883). Zigbee2MQTT will then react to this message.

Zigbee2MQTT basic message syntax

In the MQTT OUT nodes we are using the set functionality of Zigbee2MQTT, so every thing we set will overwrite the settings we want to change, the other remains untouched. The messages Zigbee2MQTT receives are simple json objects with attributes. Here we will only describe the 4 functions we implement.

Change light state

This intent sets the zigbee device on of it depends on the users request.

{"state": "ON"}

This will turn the zigbee device on. Instead of "ON" you can also write “OFF” to turn the light off.

Set brightness

This intent delivers a number between 0 and 100, this will be the brightness of the zigbee device in percentage. The function transform input scales the number between 0 and 255.

{"brightness": 128} 

This sets the brightness to the value 128, it is 50% of the maximal brightness.

Change light color

This intent passes us a color written as a string it could be something like "blau", "rot", "gelb", "grün", "lila" or "weiß". The function transform input converts the written color into a hex value that Zigbee2MQTT can understand.

{"color": "0xFFFFFF"}

This message sets the color to the hex value "0xFFFFFF" which is equal white.

Change color temp

This intent passes us one of two temperatures. It can either be "warmweiß" or "kaltweiß". The function transform input sets "warmweiß" to the value 400 which is a nice warm yellow light and "kaltweiß" will be set to 50 which is a freezing white color.

{"color": 400}

This message sets the color temperature to a warm color. The value can be everything between 0 and 512.