Internet of Things for solving my Fridge problem

Last year we got our kitchen remodeled which meant getting new kitchen cabinets and new appliances.  We had an old Kitchenaid fridge which did not fit into this new decor. We decided to get a new fridge and I started doing my market research. I did the usual stuff which included going to forums and consumer reports and eventually settled on Frigidaire.

Frigidaire – New Fridge

KitchenAid – Old Fridge

I wanted to get rid of our old Kitchenaid fridge but our usual temptation of holding on to all old things prevailed and I am glad we did that. Now that we had 2 fridges, we also means to compare one fridge over the other. We started doing that very soon as we noticed that our old fridge was retaining the freshness of fresh produce much longer. We attempted to resolve this issue by making the fridge colder but that resulted in ice forming on items placed inside the fridge and did not help in retaining the freshness of vegetables. We played with the temperature settings for a while. I called the company support and complained that fresh produce is spoiled faster. They essentially told me that nothing is wrong with my fridge.

So we kind of lived with this problem and tried to ignore the issue. No matter what we did, fresh vegetable would get spoiled faster in our shining new frididaire fridge.

Finally came Internet of Things at rescue. I reckoned that if I can place an IOT device in my fridge, I would get all the information needed and I can then chalk out a plan on how to go around this issue. And it also would help me in figuring out this whole IOT technology and at the same time, get something useful out of it.

So I got recommendation from my friends on what product to go for. Based on the feedback, I decided to get Raspberry Pi along with DHT 22 humidity and temperature sensor. This sensor turned out to be reliable. (https://www.adafruit.com/products/385).

The picture shows my setup, It costed me around $100 along with a battery for power source.( Not shown in the picture). One does not need a battery and can use any USB based charger.  If I exclude the battery, the whole setup was around $50. As you can see, the sensor is attached to another board and that turned out to be a great help. I could keep the Raspberry Pi board outside the fridge. This was important as the board would not work properly once temperature went below 6 degree C.

Once I had it all wired up, I started getting the data. I connected the data feed to google spreadsheet so that I can do my analytics easily.

Analytics

To get the analytics, I placed DH22 sensor in my old fridge (Kitchenaid) and let the sensor do the magic of sending the data feed. I let the sensor stabilize and ignored the initial numbers given the residual effect as I was placing the IOT in my fridge. Once it stabilized, I started collecting data and I continued the collection process till I started seeing a pattern, As shown in the figure, it was clear that fridge operates in a cyclic manner, The thermostat has upper and lower limit and it kicks the refrigeration process once inside of the fridge reaches a upper threshold number and it keeps working on it till it reaches threshold min value. Once it gets to that, it stops till the max threshold is reached.

Based on the observation, we noticed

1. Average Duration of the cycle – 40 Minutes

2. Max Temperature – 5 degree C and Min Temperature – 4.5 degree C

3. Max Humidity -17.3 % and Min Humidity – 11.2 %

Temperature Variance – 0.5 degree C

Humidity Variance – 6.1 %

This was very nice as this essentially meant that all my food items were not facing too many fluctuations.