While trying to use a separate power source for a simple DHT11 circuit, the DHT11 overheated, starting to melt a little in the rear. The setup was using a breadboard power supply for the + and - pins on the DHT11, and using a type C USB connector to power the Seeeduino Xiao, with PIN_2 connected to the DHT11 data. I used 5V as the DHT11 range was from 3.0V to 5.5V. I also had the pullup resistor (10k) on the + and data pins per the datasheet for the DHT11.
The code I used was the Arduino example code. The Serial monitor kept giving me the error that it could not get a reading for the temperature or humidity. When I placed the wires back on the Xiao 5V pin and ground, the temperature immediately worked, but it was at 130 degrees F, and came down slowly to the real room temperature, which was around 64F.
Any ideas why this happened? I assumed it would not pull more current than it needed. The breadboard was set to 5V.
These sensors often get overheated due to wrong connection. I request you to check your connection including the continuities of your jumpers. I also request you to check your power supply voltage with a multimeter. Sometimes cheap power supplies give more output than the mentioned value.
Here is a discussion about a similar problem with DHT11: https://forums.raspberrypi.com/viewtopic.php?t=77358
If you have an ESP8266, you can try this following circuit:
Room Temperature Over Internet With BLYNK ESP8266 & DHT11 - Share Project - PCBWay
As, ESP8266 operates at 3.3V, you can observe if your sensor behaves normally in this setup. If nothing helps, probably you got a bad sensor.
Thank you for responding, tepalia02. I appreciate your quick, thoughtful response.
I did check the breadboard power supply with my multimeter, with the jumper set to 5v and 3.3v, and both readings were correct. I then decided to check the Xiao on both the 3.3v and 5v pins and they also were correct. The Xiao, as a power supply, gave a temperature reading just fine.
Also, I substituted a DHT22 (same pinouts), and it would not work on the breadboard power supply either, although it showed no signs of overheating like the DHT11. It also worked just fine on the Xiao power supply.
Finally, I checked my 10k pullup resistor, and it was correctly 10k (@ 9850 ohms).
I got the DHT11 with my Elegoo hobby kit few years ago and the DHT22 I ordered from Ali Baba last winter, so it’s not a matter of a crappy company (as far as I can tell).
I am perplexed.
Do you have an Arduino? Then I suggest you to try this simple Arduino tutorial: DHT11 Arduino Interfacing - The Engineering Projects
Power up your Arduino from your computer’s USB port. Then see if you get a realistic value or not. This way you can find if your sensor is good or not. If still you do not get any exact value, I think you have to toss the sensor away.
