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By SentinelAeon
#85400 Hello,

I am using ESP8266 to have a simple control system for temperature and humidity. Right now i use some cheap DHT11 i ordered of ebay. Its working fine but i read that with time, this sensor will be less and less acurate so i am looking into possible solutions. Help me decide between:

1) Replace the DHT11 with a new DHT11 every few months or years. If this is the best solution, how often i would have to replace the sensor to have it accurate to 1C. Meaning if the real temp is 30C, i am ok with it showing 29C or 31C, but anything more is not ok. If i replace the sensor once a year, will i keep that 1C accuracy ?

2) upgrade DHT11 with a better more expensive sensor, that will remain accurate longer. If this is a way to go i have a couple of things that the new sensor must have. It would be great if it would have the same 3 pin setup as my existing DHT11 - this way i dont have to put the device apart, i can just swap the sensor which can be done easily. And, it would be great if the sensor could be run on 5V, same as DHT11. Like i said, getting to the actualy ESP8266 and swap cables is hard cause its inside a closed box. Sensors are outside and its easy to swap them. As far as temps go, i need it to be able to read between 10C and 40C, humidity between 0% and 100%. I would like libraries to be written for that sensor so i dont have to deal with the new code.
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By btidey
#85413 The stability over time of this type of sensor is dependent on the conditions in which it is operated. Dust and high humidity (>90%) will tend to degrade the humidity sensor fairly quickly. If you can avoid those then it will last much longer.

The accuracy of the dht11 is fairly poor even when new (+/- 2C temp +/- 5% humidity). The DHT22 has better initial accuracy (+/- 0.5C +/- 2.5% humidity) but you still need to operate it in a reasonably benign environment. The pin out and operation is the same as dht11 but the package is bigger and the sampling rate a bit slower.
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By Bonzo
#85422 I have had a BME280 temperature, humidity and pressure sensor ( make sure when buying as it gets confused with the BMP280 )

It has been in my greenhouse and has worked faultlessly for a year. I tried a DHT22 but it failed quite quickly and that was inside while I was testing the setup.

I am not sure how accurate it is as I only take a reading every 15min and it is not critical. We use the BMP on a sensor at work and I would not think it would be use if it were not reliable. I am told the Sensirion is more accurate but we need to keep the price down!

I 3D printed a housing for it and should have made some more slots for air flow but as it was going outside at the time I kept the holes to a minimum. I am glad I didn't put it outside as it was printed with PLA which is bio degradable!