David Findlay

a man, a plan, a cake: nirvana

Spark Core Freezer Monitoring Success

After installing the Spark Core as a freezer monitor last night, I ran curl in a while loop in bash to pull the temperature reading every minute overnight and append the results to a text file. This morning, after a little bit of sed and grep tweaking, I pulled the readings into Numbers and charted them:
Freezer Temperature Chart
You can see that the temperature rises to around 3. The compressor then kicks in and lowers the temperature to around −3. The temperature then slowly rises up to around 3 again, and so on — illustrating the hysteresis of the temperature control system in the freezer.

I wrote a Python script to automate the process of grabbing the result, parsing the JSON and adding the result to the table being charted in the spreadsheet:

This isn’t particularly practical, but was interesting to see nonetheless. My main goal is monitoring, so I will drop the charting part in favour of a simple notification to my phone via
Prowl.app when the temperature gets too high.