humidity sensor dht11 drop down reading

[mshh]

I use humidity sensor dht11 to measure humidity of a room, it was working good for almost a month. and suddenly the reading drop down to 10% and **** there. I calibrated it using procedures in its datasheet but the problem still exists. it works for 2 hours then drop to 10%. what is the deal?

 

[KlausST]

Hi,

Without my crystal ball it´s hard to guess. You don´t give useful informations.

My guess: Your power supply voltage drops.

Klaus

 

[mshh]

the same power supply is used for microcontroller and lcd, so if it drops MCU and LCD should drop,right? but this doesn't happen

 

[baileychic]

Check how much power supply drops. If you are using PIC then PIC can work from 3.3V to 5V. So, if power supply drops by 1V then your PIC will be still working and also Lcd but not DHT11 properly.

 

[KlausST]

Hi,

You don´t show us your schematic,
we don´t know about power supply, it could be a battery it could be regulated or unregulated....

The problem could be temperature, it could be a software problem...
We can only use the informations you give....

Klaus

 

[d123]

Hi,

Not sure if related, the humidity sensor I have has a little ...flaw?. I've attached the datasheet for you to compare and consider if it may be the same issue. View attachment Sensor Humidity HIH5030-100 Honeywell.pdf Notes on page 2 say:
3. Non-condensing environment. When liquid water falls on the humidity sensor die, output goes to a low rail condition indicating no humidity.
Extended exposure to >90 % RH causes a reversible shift of 3 % RH.

There are application notes that may be of some or no use to you...

View attachment Humidity Sensor Theory and Behavior.pdf
View attachment Humidity Sensor Performance Characteristics.pdf
View attachment Humidity Sensor Moisture and Psychrometrics.pdf

"Performance Characteristics" and "Theory and Behaviour" might be of most interest/relevance, or not. All still worth a read.