This is an Raspberry Pi based temperature and humidity logger that uses 2 (works also with 1) Adafruit DHT22 sensors for measurements. You might have seen similar kind of instructions before, but this one has a twist. It doesn't just read temperature and humidity from sensors, but it stores data to MySql database and provides means to read that temperature data with any web enabled device (computer, phone, tablet) web browser. This logger also allows you to set limits for temperatures and is able to send email if sensor temperature drops below set limit...this neat feature can be for example used to alarm when it is time to set heating on in your house / carage / greenhouse / you name it.
To complete this instructable, you will need following:
- Raspberry PI (I used Raspberry PI 1 model B+, but should be doable with other models as well)
- Power supply for the pi. (I used old Nokia microusb telephone charger which gives about 880mA)
- SD memory card. Note that you might need adapter. (I used 8Gb and had 4.1Gb available after installing everything)
- Ethernet cable or USB wlan dongle that is supported by Raspberry Pi (google can help with this)
- DHT22 sensor/s and 4.7 kOhm resistors. Instructable supports 2 sensors, but can be done with 1. https://www.adafruit.com/products/385
- Cables and breakout for connection https://www.adafruit.com/products/914
- Computer where you set up the SD card for the raspberry PI and from where you can connect and do the configurations. (NOTE: this instruction uses PC)
- Optional: Breadboard. Test assembly is easier to be created on this, than by connecting wires directly to sensors: http://thepihut.com/products/raspberry-pi-breadbo...
Internet connection is also require in location where you are going to set the raspberry logger. Either via ethernet or wlan dongle.
Keyboard + display are needed as well while installing and configuring the Wheezy OS. But once installations are finished, network is up and SSH enabled, it is possible to use connect raspberry pi remotely from PC and keyboard + display can be put aside.
NOTE- Assembly image updated 19.11.2015. There was error in last edition. -NOTE
Create assembly as instructed in attached image. Image instructs how you can connect two DHT22's to the Raspberry Pi, but if you have only one available just ignore another one and add one.
Notable here is that you can connect sensors to any GPIO you like. I had mine connected in GPIO22 and GPIO23. Both sensors also need +3.3Volts and ground. Resistor is set between +3.3V line and GPIO line.
When assembly is ready, prepare SD card and go to next step.