DHT22 getting lost on Plus Uni

[UmmelGummel]

Hallo there,

I‘ve got a Shelly Plus Uni to Control my garagedoor. 

VAC1 and VAC2 are connected to 20VDC from the Garagedoor-Control-Unit. 
OUT1 triggers the door to open/close. 
IN1 and GND are connected to a NC reed switch to indicate if the door is open or closed. 
Sensor VCC, DATA and GND Are connected to a DHT22 Sensor. 
 

After connection the power supply the setup is working fine for a couple of minutes. Then the DHT22 cant be read anymore. 

shelly_dht22.cpp:81 Error in DHT sensor reading!

Restarting the Shelly doesnt get the DHT22 back to life. 
reconnect power to the Shelly or DHT22 solves the problem for a few minutes. 
 

Firmware is 20241011-114444/1.4.4-g6d2a586

[terae]

Are you sure you have the original sensor or is it just cheap copy ones which may or may not work?

[BoeserBob]

Hi there, 

in my experience the serial communication of the DHT22s are VERY sensitive to EMC.

Maybe the motor of the garage door produces too much of that.

I only use BME280s, but I don't know if they work with the Shelly Plus uni. 

Grüße,

Robert

[Dreckfresse]

4 hours ago, BoeserBob said:

BME280s

Diese verwenden:

Interface

I²C and SPI

Daher gehen diese nicht an Shelly UNI oder AddOn

 

[UmmelGummel]

Ordered some new DHT22. 
Maybe the one I am using is broken. 
voltage is 3.3V and stable. 
Data is getting lost without Starting the Motor. 

[BoeserBob]

DHT22 needs pullup resistors to work properly, are they installed?
How long is the wiring? Maybe it's too long and catches noise?

Edited December 1 by BoeserBob

[UmmelGummel]

Wiring about 40cm. 
havent installed pullup by myself. 
read about preinstalled ones. 
how to messure? VCC to data?

[BoeserBob]

Wiring is described here für Arduino: 

Arduino - DHT22 | Arduino Tutorial

The 4 pin sensors don't have a pullup resistor. The 3Pin modules mostly have one.

 

[terae]

My testbed has about 1 meter LiYY 3x0,25 wiring and have no problems without any extra resistors when connected to Shelly devices... 🤔