Falling edge detection with JSON payload

I have some sensors that are set up to send their data via MQTT to NR in JSON format. When they detect, they appear similar to:

image

I want to send an email notification when the battery drops below the warn threshold. Basically, when a battery is new, it reports as battery_ok=1. When it gets below whatever Acurite determines warning level, it switches to battery_ok=0. I can detect this with a falling edge node easily by using a change node to break the battery_ok value out, but then I don't have the rest of the message intact. The other nodes in the triggers (e.g., deadband) seem to allow selection of the property desired (e.g., msg.payload.battery_ok).

The reason I would like to keep it, is so I could do smarter things with the notification. For the weather station, I only have 1. However, I have an array of Acurite tower sensors and it would be much cleaner and more maintainable to be notified for each sensor with a single rather than 1 flow hard coded for each sensor.

[{"id":"a2a32d63.97ea78","type":"mqtt in","z":"6f1f8b48.e80634","name":"Acurite-5n1","topic":"rtl_433/Acurite-5n1/2825/#","qos":"2","datatype":"json","broker":"b2400571.717f88","x":110,"y":60,"wires":[["504cb7c9.699908"]]},{"id":"504cb7c9.699908","type":"switch","z":"6f1f8b48.e80634","name":"filter by seq","property":"payload.sequence_num","propertyType":"msg","rules":[{"t":"eq","v":"0","vt":"num"},{"t":"gte","v":"0","vt":"str"}],"checkall":"true","repair":false,"outputs":2,"x":290,"y":60,"wires":[["5d50bf19.7e3568"],[]]},{"id":"5d50bf19.7e3568","type":"switch","z":"6f1f8b48.e80634","name":"","property":"payload","propertyType":"msg","rules":[{"t":"hask","v":"payload.battery_ok","vt":"msg"}],"checkall":"true","repair":false,"outputs":1,"x":450,"y":60,"wires":[["f0953c6c.be9a4"]]},{"id":"6a3e9be9.3568dc","type":"falling-edge","z":"6f1f8b48.e80634","name":"<0.5","threshold":"0.5","x":610,"y":60,"wires":[["87989dc2.6dc8e8"]]},{"id":"87989dc2.6dc8e8","type":"deduplicate","z":"6f1f8b48.e80634","name":"","keyproperty":"","registryclass":"","expiry":"86400","x":790,"y":60,"wires":[["8099434.fedd5c"],[]]},{"id":"8099434.fedd5c","type":"change","z":"6f1f8b48.e80634","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"Weather station battery low","tot":"str"},{"t":"set","p":"payload","pt":"msg","to":"Acurite weather station battery has dropped below 100%.  Replace at soonest convenience.","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":980,"y":60,"wires":[[]]},{"id":"f0953c6c.be9a4","type":"change","z":"6f1f8b48.e80634","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"msg.payload.battery_ok","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":540,"y":120,"wires":[["6a3e9be9.3568dc"]]},{"id":"b2400571.717f88","type":"mqtt-broker","name":"RPi3","broker":"192.168.0.200","port":"1883","clientid":"","usetls":false,"compatmode":false,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","closeTopic":"","closeQos":"0","closePayload":"","willTopic":"","willQos":"0","willPayload":""}]

Perhaps I can set msg.payload to the battery_ok value and retain the remainder of the JSON packet? I don't know how to do that and my quick attempt did not succeed. It replaced the entire msg.payload with the single value of battery_ok.

[{"id":"204b24ae.b9f4d4","type":"inject","z":"6f1f8b48.e80634","name":"","props":[{"p":"topic","vt":"str"},{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"test","payload":"{\"time\":\"2022-07-10 22:30:51\",\"model\":\"Acurite-5n1\",\"message_type\":49,\"id\":2825,\"channel\":\"A\",\"sequence_num\":0,\"battery_ok\":0,\"wind_avg_km_h\":0,\"wind_dir_deg\":157.5,\"rain_in\":110.47,\"mic\":\"CHECKSUM\"}","payloadType":"json","x":110,"y":180,"wires":[["c4cb371b.bea128","bc595a98.21cd28"]]},{"id":"c4cb371b.bea128","type":"debug","z":"6f1f8b48.e80634","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":300,"y":160,"wires":[]},{"id":"bc595a98.21cd28","type":"switch","z":"6f1f8b48.e80634","name":"","property":"payload","propertyType":"msg","rules":[{"t":"hask","v":"battery_ok","vt":"str"}],"checkall":"true","repair":false,"outputs":1,"x":270,"y":200,"wires":[["6ab9ea8e.4ef3fc","ca7c3e7b.5b7098"]]},{"id":"6ab9ea8e.4ef3fc","type":"change","z":"6f1f8b48.e80634","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload.battery_ok","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":360,"y":260,"wires":[["726e8d54.ddcf4c","8cfb1949.5cf4e8"]]},{"id":"726e8d54.ddcf4c","type":"falling-edge","z":"6f1f8b48.e80634","name":"<0.5","threshold":"0.5","x":530,"y":280,"wires":[[]]},{"id":"8cfb1949.5cf4e8","type":"debug","z":"6f1f8b48.e80634","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":550,"y":240,"wires":[]},{"id":"ca7c3e7b.5b7098","type":"debug","z":"6f1f8b48.e80634","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":430,"y":200,"wires":[]}]

Just use a switch node and switch on the property as it is a JS Object you can reference this directly through the actual incoming message

It will be something along the lines of msg.payload.battery_ok - switch one way if it s 0 or the other way (into your normal flow stream if it is 1)

Have all the sensors report in on a wildcard MQTT topic and then the first step is to switch them based on battery state - if battery is low then they go off to the warning stream which can break out the identifiers for you

Craig

My RPi that feeds the sensor data crashed and my backup was faulty. I'm going to have to rebuild that before I can fix this issue. When that's resolved, I'll test your recommendation.