# KNX Water Leakage Sensor: Convert Alternating 0|1 to Alarm Flag
**URL:** https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100
**Category:** General
**Created:** [14 July 2022 14:39 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100 "2022-07-14T14:39:58Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@mathias-ewald](https://discourse.nodered.org/u/mathias-ewald)
#### Post date: [14 July 2022 14:39 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/1 "2022-07-14T14:39:58Z")
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
---
### Author:  [@iiLaw](https://discourse.nodered.org/u/iiLaw)
#### Post date: [14 July 2022 15:40 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/3 "2022-07-14T15:40:39Z")
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.
> [@How to share code or flow json](https://discourse.nodered.org/t/how-to-share-code-or-flow-json/506/8):
>
> @dclear thanks - have updated the guidance to match
---
### Author:  [@mathias-ewald](https://discourse.nodered.org/u/mathias-ewald)
#### Post date: [14 July 2022 15:48 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/4 "2022-07-14T15:48:35Z")
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 😃
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [14 July 2022 16:03 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/5 "2022-07-14T16:03:17Z")
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.
---
### Author:  [@iiLaw](https://discourse.nodered.org/u/iiLaw)
#### Post date: [14 July 2022 17:40 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/6 "2022-07-14T17:40:34Z")
This is the msg from a Gira PS3 button to turn lights on
```auto
{"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"}
```
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [14 July 2022 19:41 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/7 "2022-07-14T19:41:07Z")
I am confused, what has that got to do with determining whether there is an alarm state or not?
---
### Author:  [@iiLaw](https://discourse.nodered.org/u/iiLaw)
#### Post date: [14 July 2022 20:20 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/8 "2022-07-14T20:20:55Z")
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 ?
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [14 July 2022 20:29 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/9 "2022-07-14T20:29:21Z")
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.
---
### Author:  [@mathias-ewald](https://discourse.nodered.org/u/mathias-ewald)
#### Post date: [15 July 2022 06:07 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/10 "2022-07-15T06:07:51Z")
Good morning 🙂 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 😃 I might have configured the Trigger node wrong but I still get alternating true/false from it just with a delay:
```auto
[
{
"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"
]
]
}
]
```
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [15 July 2022 07:25 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/11 "2022-07-15T07:25:47Z")
> [@mathias-ewald](#):
>
> I might have configured the Trigger node wrong
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.
---
### Author:  [@mathias-ewald](https://discourse.nodered.org/u/mathias-ewald)
#### Post date: [15 July 2022 08:09 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/12 "2022-07-15T08:09:47Z")
Nice. I read that option but didn't understand its purpose. Works now, thanks!
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [29 July 2022 08:10 UTC](https://discourse.nodered.org/t/knx-water-leakage-sensor-convert-alternating-0-1-to-alarm-flag/65100/13 "2022-07-29T08:10:36Z")
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