Change Node - Understanding data manipulation

General
1

I am pretty sure this is a simple question, I just can't wrap my head around JSON or expression to get it to do what I want. And I havent found a post or information on the node to help me.

I have successfully input MQTT message from Topic "tasmota1/stat/RESULT" and output it to "tasmota2/cmnd/Dimmer"

Thats half of what I need. The problem is the payload is

{"POWER":"ON","Dimmer":70}

This gets read in and sent out. I need to only send the number. the "Dimmer": value will be 10-100.

Can someone help me understand how to delete out everything but the number at the end? The flow should look like

MQTT in
tasmota1/stat/RESULT
{"POWER":"ON","Dimmer":50}
Change to
tasmota2/cmnd/Dimmer
50
MQTT out

If it is possible to split the message I could get rid of my Change State node that turns on/off Dimm2 if Dimm1 is turned on/off.

MQTT in
tasmota1/stat/RESULT
{"POWER":"ON","Dimmer":50}
Change to
tasmota2/cmnd/POWER
ON
tasmota2/cmnd/Dimmer
50
MQTT out

Any help would be greatly welcomed!
Thanks

2

Example flow (includes a switch node to filter for the power on/off):

[{"id":"d27bb630.688b48","type":"change","z":"eb446011.5548a","name":"","rules":[{"t":"move","p":"payload.Dimmer","pt":"msg","to":"payload","tot":"msg"},{"t":"change","p":"topic","pt":"msg","from":"tasmota1/stat/RESULT","fromt":"str","to":"tasmota2/cmnd/Dimmer","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":536,"y":240,"wires":[["5708c750.d0c9f"]]},{"id":"59aaf8d8.614a88","type":"inject","z":"eb446011.5548a","name":"","topic":"tasmota1/stat/RESULT","payload":"{\"POWER\":\"ON\",\"Dimmer\":70}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":146,"y":264,"wires":[["240be2f9.07e63e"]]},{"id":"5708c750.d0c9f","type":"debug","z":"eb446011.5548a","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":722,"y":240,"wires":[]},{"id":"240be2f9.07e63e","type":"switch","z":"eb446011.5548a","name":"Power ON/OFF ?","property":"payload.POWER","propertyType":"msg","rules":[{"t":"eq","v":"ON","vt":"str"},{"t":"eq","v":"OFF","vt":"str"}],"checkall":"true","repair":false,"outputs":2,"x":330,"y":264,"wires":[["d27bb630.688b48"],[]]}]

Use a change node:

Screenshot 2020-01-16 at 07.43.01
Screenshot 2020-01-16 at 07.43.011018×728 56.2 KB

Read the documentation on how to work with messages

3

Thank you so much for your extremely fast response. You made more progress in 3 hours than I did in weeks. Thanks for the reading, I hope to get to it today.

I have been busy today so didnt really get to test it, but it doesn't work. Your well written response sends object and apparently my dimmer sends string. I am sure I can figure it out and make yours work with just a click of the button, just didnt have time to get into it today.

Thanks again for your very simple flow. It is smaller and more powerful than what I was able to make.

4

the MQTT in node can be configured to deliver either a string or a parsed object....