KNX Water Leakage Sensor: Convert Alternating 0|1 to Alarm Flag

General
1

Hi there,

I have a KNX water leakage sensor that sends nothing to the group address when there is no water detected. When there's a leakage it begins sending alternating zeroes and ones to the group address.

In Node-RED I want to convert this to a simple flag that indicates if there's an alarm (1) or not (0). Being new to Node-RED I have no clue how to approach this.

Any ideas?

cheers,
Mathias

3

ok we need a bit more what KNX node are you using> Ultimate?
can you copy your flow and paste into this thread pls flow these instructions.

4

There is no flow, yet, since that's what I am trying to figure out. I use KNX Ultimate and created a "KNX Device" node with the respective group address in KNX. When I connect a debug node, there is nothing. The devices does not emit any messages. When I spill water on the sensor, the messages keep coming with payloads alternating 0 and 1:

So, when there's
no alarm: ... nothing, no message
an alarm: 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, and so on

I think the idea of the device is to connect an light that will flash when there's a water leak, but I'd prefer to get message on the phone somehow :smiley:

5

You could use a Trigger node set to send the alarm message every time there is a message in. Set the timeout to greater than the longest time between the 0/1 messages and then to send the alarm off message. Follow that with a Filter node to suppress the repeated alarms, so you will get an alarm on when the first transition occurs and then an alarm off when the input stream stops.

6

This is the msg from a Gira PS3 button to turn lights on

{"topic":"10/1/3","payload":true,"devicename":"local bus","payloadmeasureunit":"unknown","payloadsubtypevalue":"On","knx":{"event":"GroupValue_Write","dpt":"1.001","dptdesc":"Switch","source":"1.1.1","destination":"10/1/3","rawValue":[1]},"_msgid":"56649462.bbe86c"}

image

7

I am confused, what has that got to do with determining whether there is an alarm state or not?

8

It is an example of a working KNX device that uses the same Data type the Mathias should see with his device.

@mathias-ewald are you monitoring via ETS group monitor to see 0/1 values ?

9

Oh, sorry, I thought that message had come from the OP.

In terms of detecting the alarm it doesn't matter what is in the message if using the Trigger node technique that I suggested. It is just a matter of distinguishing between a stream of messages and no messages.

10

Good morning :slight_smile: I think my KNX node works fine. I double checked the data I am seeing: It is actually true/false (not 0/1) that I am getting in Node-RED.

I tried the approach with the Trigger, but the result doesn't seem to be right. I used an Inject node at a 1s interval and a Function node to generate the true/false sequence for testing since I don't want to have to spill water behind my washing machine every time to test the flow :smiley: I might have configured the Trigger node wrong but I still get alternating true/false from it just with a delay:

[
    {
        "id": "9da7dd49afa1d6a5",
        "type": "tab",
        "label": "Flow 1",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "dd3b7f2116359ec3",
        "type": "inject",
        "z": "9da7dd49afa1d6a5",
        "name": "Clock",
        "props": [
            {
                "p": "payload"
            },
            {
                "p": "topic",
                "vt": "str"
            }
        ],
        "repeat": "1",
        "crontab": "",
        "once": true,
        "onceDelay": 0.1,
        "topic": "",
        "payloadType": "date",
        "x": 210,
        "y": 280,
        "wires": [
            [
                "b921967f8d5c1620"
            ]
        ]
    },
    {
        "id": "b921967f8d5c1620",
        "type": "function",
        "z": "9da7dd49afa1d6a5",
        "name": "True/False",
        "func": "msg.payload = context.get(\"alternate\") || false;\nmsg.payload =  (msg.payload === false) ? true : false;\ncontext.set(\"alternate\", msg.payload);\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 350,
        "y": 280,
        "wires": [
            [
                "14f68eda2ef8d1d6"
            ]
        ]
    },
    {
        "id": "c3f1d5fed9ba2bc8",
        "type": "debug",
        "z": "9da7dd49afa1d6a5",
        "name": "",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "false",
        "statusVal": "",
        "statusType": "auto",
        "x": 770,
        "y": 280,
        "wires": []
    },
    {
        "id": "14f68eda2ef8d1d6",
        "type": "trigger",
        "z": "9da7dd49afa1d6a5",
        "name": "",
        "op1": "true",
        "op2": "false",
        "op1type": "bool",
        "op2type": "bool",
        "duration": "5",
        "extend": false,
        "overrideDelay": false,
        "units": "s",
        "reset": "",
        "bytopic": "all",
        "topic": "topic",
        "outputs": 1,
        "x": 620,
        "y": 280,
        "wires": [
            [
                "c3f1d5fed9ba2bc8"
            ]
        ]
    }
]
1 Like
11

Sorry, I should have said to set 'Extend delay if new message arrives'. That stops it sending the false message until no input is received for 5 seconds.

1 Like
12

Nice. I read that option but didn't understand its purpose. Works now, thanks!

13

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