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Wemos D1 R2, DS18B20, 4 Relays - Strange behaviour of thermometers on 12V supply

fafer11 426 3
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  • #1 19629116
    fafer11
    Level 10  
    Good morning
    I have a strange problem.
    Plugged into wemos board 4 relays 2x thermometer.
    When powered by usb everything works fine but....
    After connecting to 12v and switching on any of the relays, the thermometers go berserk, one erases the 5c temperature and the other -5c
    Relays pinned to gpio pins 2,12,13,14 1-wire to gpio-0.
    Can someone enlighten me as to why this is happening?
    Greetings.
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  • #2 19629419
    khoam
    Level 42  
    What is the load capacity of the 12V power supply? Are the relay coils connected to this +12V? Are the abnormal measurements all the time when any of the relays are switched on, or only momentarily after they are switched on? It would also be useful to know how these relays are connected to the Wemos.
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  • #3 19629797
    fafer11
    Level 10  
    1. 2A
    I did not plug in the relays loosely. This is an X4 relay card such a standard one from China. Power goes from the Wemos 5V.
    The bad measurements are all the time and are repeatable.
    I can add that ESPEasy is uploaded.
    I measured the power on the 1-wire at USB is less than 5V and drops when more coils are attached. At 12V there is a constant 5V. :) Paranoia.
  • #4 19629823
    khoam
    Level 42  
    fafer11 wrote:
    This is an X4 relay card such a standard one from china. Power goes from the wemos 5V.
    .
    If the Wemos is powered from 12V (rather than USB), the current output of the 5V regulator on this board is quite poor and certainly less than if you power the board from USB (in which case this regulator is not used). So I would not power the relay board from the 5V pin of the Wemos.
    Wemos board schematic: Link .
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