Nuts and Volts - December 2015

powered data logger with the SHT11 sensor module. I attached the batteries so I could put it in my car overnight where I knew the temperature and humidity changes would be more dramatic than inside my home.

Figure 7 shows communications with the data logger via my Android phone. Sadly, iPhone users are not allowed access to serial Bluetooth modules, so this won’t work for you (I’m exploring options for a future column). You’ll notice the last command displayed, THNOW, shows the time, temperature, and humidity. When logging is activated, a string like this is written to the target file every minute (the logger lets you set the number of samples to read).

In Figure 8, you can see that I opened the file using OpenOffice Calc, and then created a graph of the temperature and humidity measured in my car while I was sleeping. What I find particularly interesting is that the humidity jumps near sunrise, even though the temperature is still falling slightly.

Okay, then. Whether you’re building a greenhouse controller as I hope to do, or just want to know what’s going on in your environment, the SHT11 module will let you do it.

Have fun with this data logger. Since creating my parser, I have leaned toward interactive versus menu-based programs, and I’m having a great time. Give it a try. I think you will enjoy it too!