Calibrating a DHT11 Humidity/Temp Sensor?

Other Hardware Sensors
1

Hi Guys,

I'm putting together a small auto-controlled humidifier for my cigar humidor using a DHT11 sensor and a bottlecap humidifier. Right now, I have 2 issues:

A) I'm not sure how accurate the DHT11 is. The temp seems pretty close, but the humidity seems like it's 5-15 points low. How can I calibrate the sensor? I've tried wrapping it in a wet paper towel, and it read 95%. I tried the bottle cap salt method in a plastic bag.

B) The bottle cap humidifier requires 5vDC at half an amp. I don't think the arduino can power that by itself since it has to power the sensor as well. What's my best option? Old DC power supply cut back to 2W of power?

2

You need a transistor or a mosfet or a relay to turn the humidifier on and off.

The DHT11 is not accurate, use at least a DHT22, or a good humidity sensor : Adafruit Sensirion SHT31-D [Temperature & Humidity Sensor] : ID 2857 : $13.95 : Adafruit Industries, Unique & fun DIY electronics and kits

There is a procedure to calibrate the DHT11. It needs to be in very dry air at high temperature for a while and then in very moist air. I think it is not worth it to do that for such a cheap sensor, it is easier to buy a better sensor.

3

Hi,
if you really want to have accurate readings of the humidity go with the Sensirion SHT71. Way better.
here