Noble Bluetooth Presence detector one message on value change

General
1

Hey guys,

i'm fairly new to node-red and currently trying to make a flow that detects if a person comes home and then doing something once (open door, turn lights on or something else) but i can't figure out how i make the msg a one time message.

for scanning i use the noble ( Scan BLE) node and then a function block which contains

var msg1 = {};
if(msg.payload.peripheralUuid == "UUID HERE OF DEVICE") {
    msg1.payload = 50;
    return msg1;
}
else {
    msg1.payload = 25;
    return msg1;
}

but now i cant figure out how i only get one message when the scanble is finding the device when it previously didnt find it.

i tried to use the rbe node for the payload to check if it changes but i dont rly understand how the node is working internally.

greetings

2

You can keep track of found devices. Use a context/flow/global variable like an array. When a device is found, add it, whennot found, delete. Then you check each found device against the content of the array each time you scan

3

If you put an RBE after your function node then it should only pass on a message each time it changes from 25 to 30 or back.

4

thanks for the heads up

i tried the RBE after the function already but the output is toggling between 25 and 30 and back cause of the other device in range. this means that i will get a change in the value every x seconds

for reference here is the flow i currently have

[{"id":"19261bbb.65589c","type":"scan ble","z":"b0a161cd.a1e4d8","uuids":"","duplicates":true,"name":"","x":230,"y":620,"wires":[["dfc8a604.e7b45","3bf25956.b64556","6c7eae88.4341"]]},{"id":"6c7eae88.4341","type":"function","z":"b0a161cd.a1e4d8","name":"abfrage","func":"var msg1 = {};\nvar msg2 = {};\nif(msg.payload.peripheralUuid == \"ID\") {\n    msg1.payload = 50;\n    return msg1;\n}\nelse {\n    msg1.payload = 25;\n    return msg1;\n}\n","outputs":2,"noerr":0,"x":540,"y":620,"wires":[["583f16af.ad9b98","d63c1e5f.4b5e1"],[]]},{"id":"583f16af.ad9b98","type":"rbe","z":"b0a161cd.a1e4d8","name":"","func":"deadband","gap":"40","start":"","inout":"out","property":"payload","x":790,"y":540,"wires":[["e5731a5f.9246"]]},{"id":"e5731a5f.9246","type":"debug","z":"b0a161cd.a1e4d8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","x":1050,"y":420,"wires":[]},{"id":"d63c1e5f.4b5e1","type":"debug","z":"b0a161cd.a1e4d8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","x":930,"y":660,"wires":[]}]

my goal is that a payload / variable is changing only when the device is registred or not registred anymore.

5

Of course, follow my advice and it will work that way. The weekend is coming up, you have plenty of time to digg into javascripting :wink:

6

finally tried some more things and got it working like i wanted it. thanks for pointing me in the right direction