Talk to 20k sensors?



  • Hi!
    Is it possible to have a controller collect sensor data from 20,000 sensors? What I want is thousands of arduino-sensors in a room, all taking some measurement of the temperature, and reporting to a hub/controller (arduino or rapsberry pi) which in turn relays that info using a GPS-shield to a web server. I'm hoping it can be done with some cheap RF/wifi transmitters. Using for example bluetooth can be pretty costly if multiplied by 20k.



  • Wow, 20.000 Sensors in a room! 😮
    You will find here some information about the mysensors network: http://www.mysensors.org/about/network

    "A MySensor radio network can consist of up to 254 different radio nodes and each radio node can report data for 254 attached child sensors. This means that you can, in theory, manage data for up to 64516 sensors in a single radio network. If this isn't enough, you can create another parallel radio network on a different channel and there are 126 available channels."



  • Great, thanks for the quick reply.
    64k * 126 sounds more than enough 🙂 This is a Proof of Concept project I'm working on, and 20k is an extreme edge case, but still possible, so I have to take that many into account. Now to put theory into practice...



  • How many measurements would you like to get in which Intervall.
    I think you will get in serious trouble because all the nodes are talking wireless and this is not able to handle more than one client sending at the same time.
    If you want to do this wireless you have to sync all the activity fro a central Point. So you must have a "Server" which polls the Clients to get the data.

    Can you please describe what are you planing in more detail?



  • Each sensor is supposed to be attached to a box to track it's individual temperature. The boxes can move from one room to another, hooking up to that rooms controller. A room can have everything from 1 box up to 20,000 boxes. Frequency of measurements will be about 15-30 minutes for a chart to be plotted on the web server. The boxes will never be more than 40 meters away from the controller.



  • 🙂 15 minutes = 900 seconds. 20000 Nodes / 900 sec = 9550 🙂

    I you configure the NRF24 to the Maximum of RF24_2MBPS you can transmit - in theory - 2.000.000 MBit / sec = 250.000 Bytes / sec.
    250000 Bytes/Sec / 32 Byte Payload size = 7812 payloads/sec. Thats less that the requiered 9550.

    And if you must concentrate a lot of Clients on repeater nodes. you are totally lost. Forget it.



  • Why do you want to measure that many...just curious 😑


  • Admin

    @Hemliga-Arne

    What is the distance between the rooms, and is there metal in the walls between them?

    If they are close to each other, then the sensors will crosstalk between the rooms (that is, GW in room B will also hear some of the sensors in room A)



  • I'll try to handle crosstalk with software, it shouldn't matter if the data dumps arrive at one or the other GW. If it will pose a problem, wifi space getting too crowded or something, then it's possible to separate the gateways more so they dont interfere.


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