I have a recent Samsung refrigerator, which has a nasty habit of forming ice in the fan blades. Samsung refuses to further warranty it.... So, I use 2 thermist

I have a recent Samsung refrigerator, which has a nasty habit of forming ice in the fan blades. Samsung refuses to further warranty it.... So, I use 2 thermistors and a photoresistor and equipped them in my fridge. I used an Arduino Nano clone with a nRF24L01+ chip and MySensors library for getting data. The data then is posted to my MQTT server (Mosquitto) and also saved in a file. The file is parsed by a graph library and is displayed on my http://[hash].onion/fridge http://[hash].onion/fridge . Also, if I detect >45f or higher after last fridge door open event, I throw an alarm (chirp on piezo speaker and email). And yes, It's saved us at least 1 fridge load of groceries. We can't afford to buy a fridge every 3 years, even though throw-away culture sure would want us to.