My fridge broke, so I replaced the analog thermostat with an ESP2688 + relay + DS18S20 temperature sensor.
My server is getting the temperature readings every 10 seconds and is capable of switching the relay to turn the fridge on and off (once the logic is settled, I will bake it into an Arduino).
I've set it so that the server switches the relay on when the temperature is above 5°C (41°F) and off again when it's below 4.5°C (40.1°F).
A full cycle takes about 35 minutes about 5 of them cooling down (the fridge is currently empty, so there is no food "storing any coldness").
I know from my parent's house that the fridge turns on far less often (mine is about 17 years old, theirs about 3).
Is this a problem? Should I increase the temperature range, let's say from 5°C to 4°C? This way a cycle would take about an hour.
The image contains 12 hours of logged temperature data. I can't remember the change I made at around 10pm, I think I relocated the temperature sensor, but at 13:30 (1:30pm) I changed the lower temperature from 4 to 4.5.
Now, what is better for the fridge/compressor? A longer cycle or a shorter one? What is cheaper from the power consumption point of view? I can't place a power meter at the outlet because it's an integrated fridge and quite a hassle to remove it just to get to the outlet.