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PublicFlow #33
Garage temperature alert with MQTT
Shared by Anonymous on 21 Aug 2026
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About this flow
I use this to watch a cheap temperature sensor in an unheated garage. It ignores tiny changes, warns below -5 °C and sends everything else to a normal status output. Change the MQTT topic to match your own sensor.
Node-RED JSON
[{"id":"tab-garage","type":"tab","label":"Garage temperature","disabled":false,"info":"MQTT temperature warning with a dead-band."},{"id":"mqtt-garage","type":"mqtt in","z":"tab-garage","name":"Garage sensor","topic":"home/garage/temperature","qos":"1","datatype":"auto-detect","broker":"broker-home","nl":false,"rap":true,"rh":0,"inputs":0,"x":140,"y":100,"wires":[["rbe-garage"]]},{"id":"rbe-garage","type":"rbe","z":"tab-garage","name":"Ignore < 0.5 °C changes","func":"deadbandEq","gap":"0.5","start":"","inout":"out","septopics":true,"property":"payload","topi":"topic","x":380,"y":100,"wires":[["cold-garage"]]},{"id":"cold-garage","type":"switch","z":"tab-garage","name":"Too cold?","property":"payload","propertyType":"msg","rules":[{"t":"lt","v":"-5","vt":"num"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":590,"y":100,"wires":[["warn-garage"],["normal-garage"]]},{"id":"warn-garage","type":"change","z":"tab-garage","name":"Build warning","rules":[{"t":"set","p":"payload","pt":"msg","to":"Garage temperature is below -5 °C","tot":"str"}],"x":790,"y":70,"wires":[["debug-garage"]]},{"id":"normal-garage","type":"debug","z":"tab-garage","name":"Normal readings","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":810,"y":130,"wires":[]},{"id":"debug-garage","type":"debug","z":"tab-garage","name":"Cold warning","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":1010,"y":70,"wires":[]},{"id":"broker-home","type":"mqtt-broker","name":"Home MQTT","broker":"192.168.1.10","port":"1883","clientid":"","autoConnect":true,"usetls":false,"protocolVersion":"4","keepalive":"60","cleansession":true,"autoUnsubscribe":true,"birthTopic":"","birthQos":"0","birthPayload":"","birthMsg":[],"closeTopic":"","closeQos":"0","closePayload":"","closeMsg":[],"willTopic":"","willQos":"0","willPayload":"","willMsg":[]}]Visual preview
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