Temperature and Humidity Logger

I was past due for a project.  I had a technical itch that needed to be scratched.

Note the past tense. :-)

Enter the amazing Temperature and Humidity Logger 5000!  The genesis of this project idea stems from my fiance's lasik eye surgery last summer.  With the dry humidity conditions over the winter, she was experiencing painfully itchy eyes.  I got her a humidifier for the bedroom, and I'm curious how effectively it's working.

The project is to log data over time and analyze the humidity and temperature readings.  Who doesn't love some data to analyze?

The parts include:

• SPI SD card module
• DS3231 real time clock [library]
• DHT11 temperature / humidity sensor [library]
• ATmega 328 based microcontroller (Arduino Uno and Nano were used)

The general logic is:

1. read temperature, humidity, heat index
2. read date and time
3. append results from #1 and #2 to a file on the SD card
4. repeat about once a minute

I prototyped everything up using a breadboard and an Arduino Uno clone.  It looked like this:

Once I got this up and running with some [quite frankly hacked together] code [that I'm not the proudest of but this needn't be perfect], I moved forward with making it a little more permanent on a protoboard.  I also downsized to an Arduino Nano clone.  These documents helped to plot out the pin mappings between the Uno and the Nano.

I learned that soldering and physical prototyping are "development areas" for me.  Nonetheless, it came together and it worked.  Here's how it looks:

After a short stint in the upstairs bathroom, I couldn't resist pulling the card and plotting the data.  For those of us who love charts, here's a little eye candy: