Flat Monitor

When I moved back to Wellington I was curious about the living conditions of my new flat. The two big issues with New Zealand houses are the humidity and temperature. I recently purchased a 320x240 color TFT display (ILI9341) of eBay which has an optimised library for Teensy microprocessors. So I quickly connected up the following components:

• Teensy 3.0
• 320x240 color TFT display (ILI9341)
• DHT22 Temperature and Humidity sensor

I ported the code from a previous project (click here) to save some time coding. My current monitor stores 300 temperature and humidity measurements. It stores a measurement every minute so I  can view them in the form of a line graph and see what happened in the flat for the last five hours. The most recent measurement is displayed in the top right of the display.

Notice the drop and then the spike when the dehumidifier turned off and on.

Healthy humidity levels are between 40% and 60%. This is what I have observed so far. When the dehumidifier is turned off, humidity ranges between 75% and 80% (I always have some windows slightly open). When the dehumidifier is turned on it drops to around 55% before the dehumidifier switches off and switches back on when it rises above 60%. The dehumidifier is set to 50% but because it isn't in an optimum location it measures different results then at the location of my sensor.

The red line is a bit hard to see.

Temperature drops to a stable 13 °C. The apartment is partly dug out of the bank. So back wall creates a form of heat sink. Unfortunately this is not insulated at all. So when a heat source is turned of, temperatures fall back to 13 °C really fast. And as most old houses the windows are single glazing. 

Possible improvements are:

• Averaging multiple samples before storing them.
• Measure outside temperature and humidity and compare them.

Post a comment if you are interested in the code.