As mentioned in the first temperature Sensor post (way back in December of 2013) there's a lot of theoretical info on how much heat can be stored in the slab but there isn't very much practical info on how long it takes for the slab to warm up in the sun, how warm does it actually get and how fast does it cool off at night so I wanted a way to measure the temperature of the slab throughout the day.
My brother Phil is an experienced software engineer so he came up with a really cool system that allowed us to embed temperature sensors right in the slabs before they were poured. We now have the system running and we're starting to collect data.
We use one-wire digital temperature sensors from Dallas Semiconductor. There are 5 sensors embedded in the basement slab, 11 in the main level slab and 4 in the main level ceilings above the drywall. I have several spare channels that will be used to monitor outside air temperature as well as inside air temperature on both levels.
An Arduino processor (on the left) retrieves data from the sensors and a small embedded PC (on the right) collects the data and publishes it to web every 15 minutes.
The planning, modelling and engineering are finally starting to come together. Now we can monitor the temperatures of both slabs in real time. Here are the temps right now as I'm writing this post.... How Cool Is That!!
The data is stored permanently for graphing and analysis. The graph for the past eight days clearly shows the difference between cloudy days on the 6th and 7th versus sunny days on the 8th and 9th.
It's interesting to note that the slab doesn't start to warm up until late afternoon (4:00 - 6:00 PM). Following a sunny day, the slab will stay above 70 degrees for up to 12 hours.
It's already past the Spring Equinox so our heating season is almost over. I'm looking forward to seeing how the house performs next Fall and Winter.