The Wemos D1 Mini DHT shield V1 is a simple board that hooks up a DHT11 temperature and humidity sensor to the ESP8266. The data line from the sensor is connected to pin D4, which the ESP8266 uses during boot as a second TXD line. (This is why the LED flashes as you upload a new sketch: the LED is connected to D4.)
At least for the boards I’m using, this confuses the sensor completely, and it will not react to the ESP8266 trying to read data from it.
The only way to fix this then is to move the DHT22 data line to another pin. First, I cut the trace on the bottom of the PCB:
Cutting the trace between DHT22 and D4
This is how it looks like after the cut:
Trace between data line of the DHT22 and pin D4 is cut
Finally, I connected the data line from the DHT22 to pin D0:
DHT22 data line connected to D0
With the Arduino sketch adjusted to use pin D0 instead of D4, the sensor can now be read reliably.
p.s. It is possible that this problem is limited to clone boards that use the DHT22 instead of the DHT11. I now see that Wemos has discontinued the V1 version of this board. The current version uses a DHT12 sensor that communicates via I2C.
Thank you a lot!
You save me!
I wish you good luck in all your projects dude, sincerely
Yep thanks as well.. fixed our problem
Thank you for this, it came up when I was looking up what pin it was on and saved me a lot of hassle. As an alternative for cutting the trace if you can’t find a nice sharp knife you can always just snip the D4 pin off 🙂
Many thanks! 🙂 I’ve referred many people to this link lol.
-I also added a 10k resistor between pins 1vcc and 2 as a pullup, as recommended by some sketches.
Pingback: QuArK007 Blog » Blog Archive » Hackair Sensor Station
Thanks a lot! I cannot understand why they still sell this shield. Saved my day.
Best regards,
Steffen