1-wire sensors lost after some time



  • 1-wire sensors are lost after some time of usage.
    for example the recorded data (via node-red to influxdb):
    0_1552202295347_f1345be6-08b3-4641-90a1-aa9c6731b839-grafik.png

    i tried to reboot via ssh (M203 Module), this doesn't help (after the last points near 07:45).
    There is no issue in the file systems with the used MicroSD card (SanDisk Extreme Pro)
    the evok webinterface shows N/A for the defined sensors in the evok.cfg
    0_1552202563107_19807eeb-8f46-44b7-932a-00410ef853b1-grafik.png

    For cabling i use a 2x2x0,8 EIB cable. Cable length are different to the sensors (in a range of 5-15 meters)

    later i'll take pictures of the wiring points to ensure all things are ok.
    ( I think there is some issue in the 1-wire port or evok )



  • One DS18B20 is faulty. To discover this one sensor was not easy.
    Therefore, I have each data line of the sensors (heating) individually connected to the bus and then tested the 1-wire bus. (if the heating sensor data wires are disconnected, the other 2 sensors are transmitting values)
    At no time did I disconnect GND and + 5V to a sensor.
    Unfortunately the simple connection of the sensor data ware was not sufficient, because EVOK did not deliver any new values.
    Only a restart of the module could detect a functioning sensor / 1-wire bus within one minute.
    Without restart, the value comes in felt 5-10 minutes, if the bus works well ...

    6 sensor wires in one clamp, the faulty was there.
    The sensor wires are drilled together and then put in the WAGO clamp.
    0_1552235062206_IMG_20190310_124528.jpg


  • administrators

    Hello @christian,
    it is hard to see from the picture, but it looks like your sensors are connected in star topology. This is highly unrecommended and you can read more about it here: https://www.maximintegrated.com/en/app-notes/index.mvp/id/148

    Best regards,
    Martin