# Convert MQTT Topic for Gauge

**URL:** <https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953>\
**Category:** General\
**Created:** [29 October 2021 20:43 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953 "2021-10-29T20:43:38Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![gerribaldi](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gerribaldi/32/38935_2.png) [@gerribaldi](https://discourse.nodered.org/u/gerribaldi)\
**Post date:** [29 October 2021 20:43 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/1 "2021-10-29T20:43:38Z")

</div>

Hi,

i got a mqtt topic which provides a temp value.

`p4d2mqtt/sensor/Aussentemperatur_0x4/state : `  
`msg.payload : Object`  
`object`  
`value: 3.5`

How can i get the 3.5 to a gauge? I try severell things without success. Connect the mqtt direct to the gauge, via json convert and also via switch node.

Thanks & Regards  
gerribaldi

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<div class="post-metadata">

**Author:** ![UnborN](https://avatars.discourse-cdn.com/v4/letter/u/4491bb/32.png) [@UnborN](https://discourse.nodered.org/u/UnborN)\
**Post date:** [29 October 2021 21:02 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/2 "2021-10-29T21:02:07Z")

</div>

The gauge node expects the numeric _value_ to be in `msg.payload`  
yours seems to be in `msg.payload.value`  
use a **Change node** to set it to the correct property

**Example Flow:**

```auto
[{"id":"23068c7ddf151c0e","type":"ui_gauge","z":"5847b7aa62131d37","name":"","group":"26ff5dd1b85714c0","order":0,"width":0,"height":0,"gtype":"gage","title":"gauge","label":"units","format":"{{value}}","min":0,"max":10,"colors":["#00b500","#e6e600","#ca3838"],"seg1":"","seg2":"","className":"","x":670,"y":500,"wires":[]},{"id":"d47baf5779f73ba6","type":"inject","z":"5847b7aa62131d37","name":"fake mqtt","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"p4d2mqtt/sensor/Aussentemperatur_0x4/state","payload":"{\"value\":3.5}","payloadType":"json","x":320,"y":500,"wires":[["0cf0c49e7ef553a5"]]},{"id":"0cf0c49e7ef553a5","type":"change","z":"5847b7aa62131d37","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload.value","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":480,"y":500,"wires":[["23068c7ddf151c0e"]]},{"id":"26ff5dd1b85714c0","type":"ui_group","name":"Default","tab":"a2b4d00e.93a548","order":1,"disp":true,"width":"6","collapse":false,"className":""},{"id":"a2b4d00e.93a548","type":"ui_tab","name":"Test","icon":"book","order":1,"disabled":false,"hidden":false}]

```

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<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [29 October 2021 21:10 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/3 "2021-10-29T21:10:07Z")

</div>

The gauge can accept the value in any property  
instead of {{value}}  
you can us {{msg.payload.value}}  
e.g.

```auto
[{"id":"d47baf5779f73ba6","type":"inject","z":"b779de97.b1b46","name":"fake mqtt","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"p4d2mqtt/sensor/Aussentemperatur_0x4/state","payload":"{\"value\":3.5}","payloadType":"json","x":90,"y":3840,"wires":[["23068c7ddf151c0e"]]},{"id":"23068c7ddf151c0e","type":"ui_gauge","z":"b779de97.b1b46","name":"","group":"8b5cde76.edd58","order":0,"width":0,"height":0,"gtype":"gage","title":"gauge","label":"units","format":"{{msg.payload.value}}","min":0,"max":10,"colors":["#00b500","#e6e600","#ca3838"],"seg1":"","seg2":"","x":440,"y":3840,"wires":[]},{"id":"8b5cde76.edd58","type":"ui_group","name":"","tab":"8f03e639.85956","order":1,"disp":true,"width":"12","collapse":false},{"id":"8f03e639.85956","type":"ui_tab","name":"Home","icon":"dashboard","disabled":false,"hidden":false}]

```

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<div class="post-metadata">

**Author:** ![gerribaldi](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gerribaldi/32/38935_2.png) [@gerribaldi](https://discourse.nodered.org/u/gerribaldi)\
**Post date:** [31 October 2021 18:56 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/4 "2021-10-31T18:56:09Z")

</div>

Thanks a lot to everybody for the hints. It works for me in this way

```auto
[{"id":"4d8d143f287e4cb3","type":"mqtt in","z":"a130db41.078cf8","name":"Fühler Außentemp Kessel","topic":"p4d2mqtt/sensor/Aussentemperatur_0x4/state","qos":"2","datatype":"auto","broker":"40f8c1d9414e9ee8","nl":false,"rap":true,"rh":0,"x":190,"y":4040,"wires":[["cc87326c367b4017"]]},{"id":"fb97e2c00b29c422","type":"debug","z":"a130db41.078cf8","name":"1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":650,"y":3960,"wires":[]},{"id":"cc87326c367b4017","type":"json","z":"a130db41.078cf8","name":"","property":"payload","action":"","pretty":false,"x":450,"y":4040,"wires":[["fb97e2c00b29c422","d22f522462ebdea2"]]},{"id":"d22f522462ebdea2","type":"ui_gauge","z":"a130db41.078cf8","name":"Fühler Kessel","group":"5817cb8be1e74b76","order":1,"width":4,"height":3,"gtype":"gage","title":"Fühler Kessel","label":"°C","format":"{{msg.payload.value}}","min":"-20","max":"+50","colors":["#2f86bc","#00b500","#ca3838"],"seg1":"","seg2":"","className":"","x":760,"y":4040,"wires":[]},{"id":"40f8c1d9414e9ee8","type":"mqtt-broker","name":"","broker":"somewhere","port":"1883","clientid":"","usetls":false,"protocolVersion":"4","keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","birthMsg":{},"closeTopic":"","closeQos":"0","closePayload":"","closeMsg":{},"willTopic":"","willQos":"0","willPayload":"","willMsg":{},"sessionExpiry":""},{"id":"5817cb8be1e74b76","type":"ui_group","name":"Kessel","tab":"fa285b75.203de8","order":9,"disp":true,"width":4,"collapse":false,"className":""},{"id":"fa285b75.203de8","type":"ui_tab","name":"Heizung","icon":"fa-thermometer-half","disabled":false,"hidden":false}]

```

---

<div class="post-metadata">

**Author:** ![UnborN](https://avatars.discourse-cdn.com/v4/letter/u/4491bb/32.png) [@UnborN](https://discourse.nodered.org/u/UnborN)\
**Post date:** [31 October 2021 19:02 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/5 "2021-10-31T19:02:49Z")

</div>

cool .. yea @E1cid 's recommendation was simpler  
also if you set your MQTT's Output to  
 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/2/3/238055239fe7567d86217bab9208f7d61e5ee863.png)  
you wont need the Json node either and you can wire the Mqtt directly to the Gauge 😉

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<div class="post-metadata">

**Author:** ![gerribaldi](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gerribaldi/32/38935_2.png) [@gerribaldi](https://discourse.nodered.org/u/gerribaldi)\
**Post date:** [7 November 2021 19:42 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/6 "2021-11-07T19:42:37Z")

</div>

I will try, thanks 👍

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [21 November 2021 19:42 UTC](https://discourse.nodered.org/t/convert-mqtt-topic-for-gauge/52953/7 "2021-11-21T19:42:52Z")

</div>

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