Here’s a Raspberry Pi temperature monitoring project taking advantage of Adafruit’s DHT22 temperature-humidity sensor and “DHT Humidity Sensing on Raspberry Pi with GDocs Logging” Learning System project, from Reid Derby:
A few weeks ago I started planning to make my first homebrew craft beer at home and I wanted to find out what the temperature would be in my kitchen overnight. I understood that you need to keep beer fermenting between about 20 and 25 degrees Celsius and I didn’t want to come down in the middle of the night once the central heating had gone off to find out what the ambient temperature of the kitchen was.
That was when I discovered the awesome Adafruit website. I imagined that someone had already built a temperature sensor on a Raspberry Pi and as if by magic I found this DHT humidity and temperature project created by LadaAda! I ordered the breadboard, Cobbler kit, sensor and a pack of resistors and then days later (i.e. today) it all turned up in the mail.
After soldering the cobbler kit together I assembled the kit, downloaded a fresh Debian Linux image for my SD card, then plugged everything in and started on the software. I didn’t have to write anything but I had a lot of trouble getting the C code to work until I realised I hadn’t followed the full instructions and compiled the code! There is also a Python program that takes the output from the C Program and uploads a record into a Google spreadsheet for me.
I now have a lovely Google Spreadsheet which gets updated every 3 seconds with the temperature and humidity in my kitchen. I took a sample of the log and copied into a lovely little website called Datawrapper which is like an online version of Excel charts but you can embed the charts in your blog as I have done! You might notice a discontinuity in the humidity figures. This is because I stopped logging for a while during making dinner. The humidity was rising in the kitchen due to the cooking but I wasn’t measuring it! …
Featured Adafruit Tutorials!
DHT Humidity Sensing on Raspberry Pi with GDocs Logging: Time to start exploring more sensors with the Raspberry Pi! Today we’ll be checking out the DHT11, DHT22 and AM2302 humidity and temperature sensors available from Adafruit
In this tutorial we’ll be showing how to utilize C for high-speed GPIO polling to handle bit-banged sensor output. Many low cost sensors have unusual output formats, and in this case, a “Manchester-esque” output that is not SPI, I2C or 1-Wire compatible must be polled continuously by the Pi to decode. Luckily, the C GPIO libraries are fast enough to decode the output. (read more)
Featured Adafruit Products!
DHT22 temperature-humidity sensor + extras: The DHT22 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data. The only real downside of this sensor is you can only get new data from it once every 2 seconds, so when using our library, sensor readings can be up to 2 seconds old. (read more)
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