B4R Question Alternative to the DHT22 for temp & humidity?

Discussion in 'B4R Questions' started by Kevin, Sep 2, 2018.

  1. Kevin

    Kevin Well-Known Member Licensed User

    Now that I have put my temp probe issue to rest, the last thing that is bothering me is the poor reliability of the DHT22 temp & humidity sensor. For temperature, it is fine. However, humidity is pretty much a joke. It was relatively accurate on my couch, but in the real world (exposed to actual weather) it is pretty bad. If it rains (reading 100% humidity), it will often stay stuck there for days. It is also just very slow to respond to changes in humidity. I have already Googled about this and apparently that is just how they are.

    From what I have read, there are better alternatives at a higher price (which is fine), but what I want to know is if there are any other temp/humidity sensors that are currently supported in B4R and if anyone has any experience with them.

    Sensor list:
    Aosong AM2302 (A.K.A. DHT22)
    Aosong AM2320
    Aosong AM2321
    Sensirion SHT71
    Measurement Specialties HTU21D
    Silicon Labs Si7021
    Bosch Sensortec BME280
     
  2. tigrot

    tigrot Well-Known Member Licensed User

    The best way to measure humidity is to use a wet bulbe hygrometer. So you are sure that the readout of the sensor is correct.
     
  3. Peter Simpson

    Peter Simpson Expert Licensed User

    aren't those relatively expensive @tigrot?

    I've tested the Silicon Labs Si7021 and Aosong AM2302 sensors for humidity (I may have posted the code on here, I'm not sure), but as I had no reference to what the correct humidity was at the time, I can't really say how accurate they were, but they were both basically giving the same readings at the time.
     
  4. Toley

    Toley Active Member Licensed User

    I also rejected DHT11/22 for a project I'm working on. I have ordered some BME280. Still don't have them in hands but from reviews I've read they seems a lot more accurate in humidity reading and they do not cost a lot extra.
     
  5. tigrot

    tigrot Well-Known Member Licensed User

    Well it's basically two thermometers one with dry bulb and one with a fabric small tube on the bulb. The fabric is always wet . The two temps read on a two entries table has a curresponding humidity grade. Recently you can find digital instruments as well, with same basics.
     
    Peter Simpson likes this.
  6. Kevin

    Kevin Well-Known Member Licensed User

    Did you test these outside or just indoors?
     
  7. Kevin

    Kevin Well-Known Member Licensed User

    I'll be interested to hear what your experience is with it. Have you found b4r code on them? It's good to hear that they are not too much more expensive, and Bosch definitely makes some quality stuff.
     
  8. Peter Simpson

    Peter Simpson Expert Licensed User

    Hmm that's a good question, I think that I tested them by the open windows in my home office, I know that it's not as good as actually walking outside but as I was just playing about with them that's what's I most probably did knowing me.

    Hmm. cheers Kevin,
    I just ordered one of these for the fun of it, you know just to add to the collection of bits to play with in the future.
     
  9. Toley

    Toley Active Member Licensed User

    I have receive my BME280 and found some time to test it. I can say they are much more responsive in humidity measurement than any DHTxx I've tested so far. I did not made intensive test and do not have any comparative reference but only blowing on the sensor made the humidity measurement vary instantly. The only thing is temperature seems to me a bit high, I read 27C inside while it was surely under 24C. But I believe this can be calibrated.

    I do not use any B4R code I use an Arduino UNO with level translator on the I2C lines and Adafruit library. My sensor is at address 0x76 instead of the default 0x77.
     
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