Ever think to yourself, "I wonder how much that costs", or more importantly "I wonder how much that is costing me"? I wondered this about my refrigerator. Exactly how much money does it cost every time I open the refrigerator door? Well, I hope to be able to answer that question with the new Raspberry Pi and EnOcean IoT pack. My plan is to create a system where the Raspberry Pi monitors when my refrigerator door is opened, how long it is opened, and the ambient temperature. Then with the IoT pack transmit the data over my home network. With the data I can analyze the heat transfer from my fridge and hopefully calculate the cost of opening the door.


Proposed System

Figure 1 shows the intended system. The EnOcean IoT pack is essentially a set of bundled wireless sensors, of which some use a small solar panel to harvest energy, and a wireless gateway that allows the Raspberry Pi to communicate with the sensors.



Figure 1: The proposed monitoring system installed on a typical refrigerator. The EnOcean wireless temperature sensor and the EnOcean magnetic contact switch monitor the ambient temperature and the opening/closing of the refrigerator door respectively. A Raspberry Pi runs FHEM (data logging server) and logs events like opening and closing the door.


For home automation, the sensor communications have been bundled into a home automation server called FHEM. This is my first experience with FHEM, but it has been quite easy to configure for data logging. I had zero experience with the Raspberry Pi before beginning this project, but I had been using Linux as an operating system for approximately 6 years. Once I have collected enough data, I will perform the analysis and hopefully publish the results in another blog post.