Here’s a picture of data from my fridge project from today, annotated with events. Some of the events I caused, like opening doors and touching sensors to make sure that I had mapped the sensor IDs to data sites correctly. Some I didn’t, like the defrosting cycle. Some I don’t know about, like the fridge middle sensor going to zero a few times, and the first two spikes of the freezer high sensor.

In the left side of the graph, in the first place that shows fridge temperature cycling quickly, note that the middle and low fridge sensors are out of phase.

The consistent 15°C/59°F measurement at the top of the fridge compartment worries me. That’s too warm.


Michael K Johnson June 13, 2015 21:18

All six sensors were reading room temperature correctly before I installed the harness in the fridge, and that fridge high sensor read ice as being about 0°C, so it seems unlikely that the fridge high sensor is just reading far higher than true. The 18B20 sensors are supposed to be accurate to 0.5°C

Kim Johnson June 14, 2015 07:13

I do not like that top measurement either. Hmmm. But I haven’t noticed anything different about the food that is up there…

Michael K Johnson June 14, 2015 07:44

Another night of data confirms that the compressor is running almost half the time just to maintain temperature when the doors aren’t opening. I spent very little time with the doors open yesterday; less than we would on a typical day, and I put nothing warm into either compartment other than sensors and tape.

Yesterday, the compressor was off only once, for 20 minutes (from 4:30 to 4:50), between 3:30PM and 10:20PM. Then it spent all night in a pattern of about 40-50 minutes on, one hour off.

Michael K Johnson June 14, 2015 09:18

We have noticed for a long time that ice cream at the bottom of the freezer is softer than ice cream at the top of the freezer. Now we have data that shows that the bottom is indeed (somewhat counter-intuitively) warmer than the top. I assume this is because the fridge temperature regulation via a fan blowing air between the freezer and fridge compartments is at the bottom; that would make sense given that the fridge is warmer at the top and colder at the bottom.

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