The AM2302 Temp/Humidity Sensor return none value in Raspberry Pi 3 B+

Asked Jan 05 '19 at 18:49

Active Jan 05 '19 at 21:07

Viewed 624 times

I am using the AM2302 Temp/Humidity Sensor. I start with

sudo apt-get update && sudo apt-get -y install git python-dev
git clone https://github.com/adafruit/Adafruit_Python_DHT.git
cd Adafruit_Python_DHT/
sudo python setup.py install

and I connected the sensor:

"-" to GND (pin 6)
"+" to 3V3 (pin 1)
"S" (signal) to GPIO4 (pin 7)

I run the following code :

import os
import time
import sys
import Adafruit_DHT as dht
import json

while True:
    h,t = dht.read_retry(dht.DHT22, 4)
    msg = json.JSONEncoder().encode({'tem' : round(t,3),'hum' : round(h,3)})
    print msg
    time.sleep(5)

I got

Traceback (most recent call last):
  File "tem_hum.py", line 9, in <module>
    msg = json.JSONEncoder().encode({'tem' : round(t,3),'hum' : round(h,3)})
TypeError: a float is required

which means there is no data it just returns none.

I already tried these in the below links:

https://github.com/adafruit/Adafruit_Python_DHT/issues/63 https://github.com/adafruit/Adafruit_Python_DHT/issues/73 https://github.com/adafruit/Adafruit_Python_DHT/issues/44

Any suggestion to make it read both Temp/Humidity.

Thanks in Advance.

edited Jan 05 '19 at 21:07

asked Jan 05 '19 at 18:49

I_Al-thamary

What do you get if you print(h,t) after 'read_retry'? – CoderMike Jan 05 '19 at 19:02
only (none,none) – I_Al-thamary Jan 05 '19 at 19:04
Example suggests setting sensor=Adafruit_DHT.AM2302 and passing sensor into read_entry https://github.com/adafruit/Adafruit_Python_DHT/blob/master/examples/simpletest.py – CoderMike Jan 05 '19 at 19:45
@CoderMike The same result. – I_Al-thamary Jan 05 '19 at 19:54
Add a photo of your wiring. – CoderMike Jan 05 '19 at 19:55
If you change directory to the examples folder, what does 'sudo ./AdafruitDHT.py 2302 4' do? – CoderMike Jan 05 '19 at 20:42
It shows this message Failed to get reading. Try again! – I_Al-thamary Jan 05 '19 at 20:44
Have you enabled the 1-wire interface in raspberry pi configuration? – CoderMike Jan 05 '19 at 20:56
Yes, and I tried and it gives the same result. – I_Al-thamary Jan 05 '19 at 20:58
Update your question with all this info. – CoderMike Jan 05 '19 at 20:59
1

The 1-wire interface MUST NOT be enabled with the default GPIO 4 if you are using the AM2302 on GPIO 4. – joan Jan 06 '19 at 00:04
@joan Actually, I tried to apply some answer in GitHub and my sudo rpi-update 52241088c1da59a359110d39c1875cda56496764 sudo reboot and right now the raspberry pi doesn't connect at all. – I_Al-thamary Jan 06 '19 at 05:04
Your problem is unlikely to be due to software (provided you followed the instructions in your question and did not install anything else). Your code works on my Pi3B+ with a DHT11. (I normally use code written by @joan) Your wiring differs from mine (but there is no standard for sensors). You should check actual connections (and DO NOT install unsupported "fixes"). – Milliways Jan 06 '19 at 06:49
@Milliways Do you use the same "-" to GND (pin 6) "+" to 3V3 (pin 1) "S" (signal) to GPIO4 (pin 7) – I_Al-thamary Jan 06 '19 at 06:53
I use Gnd on pin 9 but this makes no difference. Some DHT modules lack pullup - but there is no consistency in connections or labelling of modules. It is easy to verify presence of a resistor by inspection or with a multimeter. – Milliways Jan 06 '19 at 06:59
I will try it. I'm trying to use minitools to copy partition and I hope it will works. – I_Al-thamary Jan 06 '19 at 07:29
I changed the sensor and it works. – I_Al-thamary Jan 07 '19 at 11:55

The AM2302 Temp/Humidity Sensor return none value in Raspberry Pi 3 B+

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