Smart Refrigerator

Hi all,

I have a standard refrigerator and it seems that the common thermostat inside it is far from “smart”, so you have to keep adjusting it if there’s a lot of things inside (or not), if the day is hot or cold, and so on. So I had this idea about to put a temperature sensor inside it and control it with a sonoff. Just leave the thermostat near maximum and let the home-assistant do the rest.
I already did the first part: put a xiaomi temperature inside and it works right (i was wondering if the signal would not pass the case). I even tried it in different places/shelves and all of them worked.
But before going into sonoff/smart plug configuration, I thougth that I may damage my refrigerator turning it on/off this way. So I kindly ask if someone (maybe a enginneer or technician) could enlighten me on this matter? :slight_smile:

p.s. I antecipate that I will have problem with the internal light, but i will deal with that later.

Its not the best to keep power cycling the compressor like that but then its not much different from the thermostat doing it…

Not to encourage busting into the fridge wiring… but you could wire your switch in series with the fridge thermostat so to act in the same way as it, which would essentially replace the thermostat given that you will be setting it to max coldness

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Well if it’s a basic refrigerator, as stated by @sparkydave, it’s already basically the way it works ! Thermostat just put on/off engine when needed :wink: Be careful if you bypass completely the thermostat to well keep in circuitry the big capacitor (most of time it’s near the engine). If you don’t keep it engine will die quickly !

Side note: I would setup your Sonoff thermostat/relay so it can not flip on or off more than one time every few minutes to avoid the classic loop when you implement very basic thermostat feature !

I really dont want to mess with wiring unless there’s a clear advantage in doing so (well there is the internal light issue, but not strong enough).

thanks for the hint about the loop. It seems that the nice folks who wrote the generic thermostat component already got this covered with “min_cycle_duration”.

Hi my old refrigerator in me interested for your design would like to know if you took it forward
If so, how would you share what you did and how you put the data in HA thank you

Not yet. I was waiting for a new sonoff to arrive and now that I got it waiting for free time again to start the mods :slight_smile:

I’ll put my news here too.:grinning:
Thankyou @clyra


I have some news. The maker of my refrigerator was nice enough to include a electrical diagram on the back, so find the right wire to tap was easier than I thought. I also did the mod on a sonoff basic to make it a “dry-contact” relay. Since I also had a sonoff pow lying around, I used it to just measure power usage. The modded sonoff was inserted between the thermostat and the compressor start relay (the number “6”, bottom wire). I also started to plot the power usage and temperature using influxdb/grafana.

It’s working, but I found that the current position of the temperature sensor is not the best and it seems to result in a great temperature variance. When the sensor reaches the target temperature and turn off the compressor, the temperature continues to drop! Right now I’m trying with another sensor and looking for the best place. I also started to use the new lovelace ui, so here’s my kitchen screen :slight_smile: (note the two temperature sensors, tmp1 is at the bottom shelf and the other near the inside thermostat button):

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ah… one more thing. Sonoff works as “normally” open relay. I’m looking to replace it with a sonoff “inching/self-locking” which you can choose normally open or close. Choosing normally close means that if i want to go back to the original refrigerator thermostat I just have to unplug the sonoff from the wall.

@clyra hello my refrigerator at the bottom has a water outlet that goes to a recepient near the motor I passed the sensor at this outlet of water inside the refrigerator


As you may soon discover, the right place to put the sensor may be tricky. The first position that I tried resulted in longer cycles of turning the motor on/off. The actual position seems to make the temperature more stable, but with a lot shorter cycles of on/off (may affect the motor life time). I think I need to find a middle ground between the two.

This is my refrigerator cycle.

I’m leaving it in the range of 6 to 8 degrees of temperature

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