Esp8266 - DHT22 - Invalid readings!

kc130up · May 11, 2025, 5:05am

I am (still) working on the air sensor project from Home Tech Hacker.

The EPS8266 & PM sensor is working as expected. The problem is the temp & humidity sensor.

Logs show:

[00:18:07][W][dht:177]: Requesting data from DHT failed!
[00:18:07][W][dht:061]: Invalid readings! Please check your wiring (pull-up resistor, pin number) and consider manually specifying the DHT model using the model option.
[00:18:07][D][sensor:093]: 'Shed Temp': Sending state nan °C with 1 decimals of accuracy
[00:18:07][D][sensor:093]: 'Shed Humidity': Sending state nan % with 0 decimals of accuracy

I’ve done a few things to no avail.
-changed the pin from D4 to GPIO2
-added the model number to the code
-changed the baud rate
-tried a different DHT22 sensor

Still get the same error. Here is the DHT22 portion of the .yaml file

sensor:
  - platform: dht
    model: DHT22
    pin: GPIO2
    temperature:
      name: "Shed Temp"
    humidity:
      name: "Shed Humidity"
    update_interval: 60s

tom_l · May 11, 2025, 5:20am

What value pull up resistor are you using?

kc130up · May 11, 2025, 1:10pm

I do not have one. Neither guide I am following mentions a resistor!

I read yesterday this model includes a pull up resistor, but now I read it does not. Darn internet.

Not even sure where to get locally get a resistor without Radio Shack…haha.

Arh · May 11, 2025, 1:20pm

Buy the sensor already on a PCB, these have the sensor on the board. But worth buying a bunch of 4k7 or 10 k resistors off eBay or aliexpress just in case though…

Karosm · May 11, 2025, 1:31pm

So do you have bare sensor or a module?
If you have doubts, post a photo of your sensor.

kc130up · May 11, 2025, 8:05pm

Looks like bare sensor.

I added a resistor between 3.3v and the D4.

Issue persists.

I know its messy. I ran out of hot glue and used tape.

I am going to try the second sensor with just the ESP8266 and the temp sensor with a resistor.

Karosm · May 11, 2025, 8:14pm

It’s definitely sensor module with pullup on board.

You could try with model: AUTO_DETECT or AM2302.
Make sure your wiring is correct.

kc130up · May 11, 2025, 8:57pm

In that case, i hope adding the resistor didn’t hurt anything.

Should I try this:

sensor:
  - platform: dht
    model: AM2302
    pin: D4
    temperature:
      name: "Shed Temp"
    humidity:
      name: "Shed Humidity"
    update_interval: 60s

I checked the wiring twice like Santa! It is only 3 wires.

I moved this to a bread board to it looks cleaner. This has the resistor added. \

kc130up · May 11, 2025, 9:12pm

This is easier to see the pins. Let me know if i am not connecting something correctly.

I tried recompiling with AUTO_DETECT and AM2302. Neither had any affect.

Karosm · May 11, 2025, 9:27pm

Your wiring looks very good to me. To take out any doubts, try with D1 or 2/5/6/7, D4 has onboard LED connected to (shouldn’t affect normally though) and generally you should avoid using strapping pins if you have clean ones available.

kc130up · May 12, 2025, 3:06am

Looks like it worked using D1…

kc130up · May 12, 2025, 3:14am