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Nodemcu does not connect to wifi when DHT22 is plugged in at startup

loosac 1191 1
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  • #1 18241224
    loosac
    Level 11  
    Hello,
    I have connected the DHT22 sensor to the nodemcu according to the tutorial from the website: https://lastminuteengineers.com/esp8266-dht11-dht22-web-server-tutorial/

    Nodemcu does not connect to wifi when DHT22 is plugged in at startup .

    If I run the bare nodmcu -connects to wifi and gets the address. The wifi network is configured correctly, the web server responds. If at this point I plug the DHT22 sensor pin into the data port everything works beautifully:

    Nodemcu does not connect to wifi when DHT22 is plugged in at startup .

    Nodemcu does not connect to wifi when DHT22 is plugged in at startup .


    On the other hand, if I plug the DHT22 into the unplugged nodemcu board and only then apply power, there is no wifi connection. Not even messages come out on the serial that I am initiating a wifi connection. I only get the strobes which are always there during startup and that's the end of it.

    Nodemcu does not connect to wifi when DHT22 is plugged in at startup .

    But that's not the point, after all, to wait until the controller plugs into the wifi and manually plug in the sensors?

    I have checked the power supply variants of the DHT22:
    - as above - i.e. power supply from the 3.3v pin from the nodemcu board
    - external 3.3v power supply
    - external 5v power supply

    Situation the same every time. Is this a known problem? I have not come across similar cases anywhere.
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  • #2 18241391
    khoam
    Level 42  
    If you feed the DATA signal from the DHT22 to pin D8 (GPIO15) and have this line connected via a resistor to the power supply, the NodeMCU will not boot after power-up. There must not be a high state on this pin during boot, afterwards it does not matter.
    https://randomnerdtutorials.com/esp8266-pinout-reference-gpios/
    You need to select a different pin and recompile the program. GPIO15 is internally connected via a resistor to ground, so its selection as input for the DHT22 is incomprehensible.
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