AM2302 Temperature and Humidity Sensor - Bat Project #01 - Durrell, Jersey

In this post I'll detail how I fared with getting a AM2302 working with the RPi.

This is the first step in a project I'm working on for Durrell Wildlife Conservation Trust. As well as working on a Gorilla feeder with my friend Max, they were also interested in data logging for their bat house:




I bought a sensor from eBay for a few pounds.

From what I can understand, the output from these devices is a digital stream of bits containing the relevant data, but it is not in a regular format like I2C, therefore you have to download a special library. I followed the instructions from Adafruit and it worked really well.

I wasn't that bothered about uploading my data to a google sheet, but since I discovered Thingspeak
a few days ago, I've been itching to try it. It's a great solution for the zoo project because the data goes straight to the web and is formatted and graphed automatically, and can be made public.

I found a great tutorial for linking python to thingspeak here:

http://www.australianrobotics.com.au/news/how-to-talk-to-thingspeak-with-python-a-memory-cpu-monitor

I just adapted the code and added it to the Adafruit example code. Resulting code is messy but worked really well.

I developed this using a model B+ but once it was running I shrunk it down onto a headless Pi Zero.

The thingspeak project site for the trial data (from my lounge) is here:

https://thingspeak.com/channels/103719

And you can embed the graphs using an iframe embed code. I presume this will update as data gets added, but I don't yet know for sure.




Hardware wise I set it up exactly as shown in the diagrams of the tutorial, but added a blue LED between the data and ground pins of the AM2302. It was a lucky guess and works nicely, flashing brightly as data is sent to the pi every minute.

(Sidenote: I've been trying out Node Red recently and I love it, but the instructions I could find online for getting the sensor to work in Node Red seem out of date and I ran into errors trying to install the nodes.)


The code:

#!/usr/bin/python
# Copyright (c) 2014 Adafruit Industries
# Author: Tony DiCola

# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import sys
import httplib, urllib
import Adafruit_DHT
from time import sleep

# Parse command line parameters.
sensor_args = { '11': Adafruit_DHT.DHT11,
    '22': Adafruit_DHT.DHT22,
    '2302': Adafruit_DHT.AM2302 }
if len(sys.argv) == 3 and sys.argv[1] in sensor_args:
 sensor = sensor_args[sys.argv[1]]
 pin = sys.argv[2]
else:
 print 'usage: sudo ./Adafruit_DHT.py [11|22|2302] GPIOpin#'
 print 'example: sudo ./Adafruit_DHT.py 2302 4 - Read from an AM2302 connected to GPIO #4'
 sys.exit(1)

# Try to grab a sensor reading.  Use the read_retry method which will retry up
# to 15 times to get a sensor reading (waiting 2 seconds between each retry).

while True:
 humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

# Un-comment the line below to convert the temperature to Fahrenheit.
# temperature = temperature * 9/5.0 + 32

# Note that sometimes you won't get a reading and
# the results will be null (because Linux can't
# guarantee the timing of calls to read the sensor).  
# If this happens try again!
#Pushing data to Thingspeak
# python

        if humidity is not None and temperature is not None:
                print 'Temp={0:0.1f}*  Humidity={1:0.1f}%'.format(temperature, humidity)
        else:
                print 'Failed to get reading. Try again!'
                sys.exit(1)


 params = urllib.urlencode({'field1': temperature, 'field2': humidity,'key':'92P5L3PGPTT8ZE8N'})
 headers = {"Content-type": "application/x-www-form-urlencoded","Accept":"text/plain"}
 conn = httplib.HTTPConnection("api.thingspeak.com:80")
 conn.request("POST", "/update", params, headers)
 response = conn.getresponse()
 print response.status, response.reason
 data = response.read()
 conn.close()


 if humidity is not None and temperature is not None:
  print 'Temp={0:0.1f}*  Humidity={1:0.1f}%'.format(temperature, humidity)
 else:
  print 'Failed to get reading. Try again!'
  sys.exit(1)
 
 sleep(60)