Part 1 of this blog discussed sensors in the laundry room in washing machines and dryers. In the kitchen, similar to the laundry room, basic functions can be designed in using established sensing techniques.
In the typical home, the refrigerator is the second-largest consumer of electricity (13.7%), with the air conditioner being number one. So, reducing energy consumption is among the major driving forces for sensor use in the kitchen.
While thermocouples can sense when ice forms on the refrigerator’s evaporator coil, this approach’s low sensitivity makes it highly inefficient. Instead, today’s smart models typically use an algorithm to trigger an automatic defrost cycle based on the amount of time the door is open, compressor run times and time since the last defrost cycle.
Image source: US20190311598A1 – Scent-based spoilage sensing refrigerator – Google Patents
Sensors or switches to detect when various portions of the refrigerator are open include freezer compartments lid sensor, ice bucket level sensor, door (freezer and refrigerator) position sensors, compartment tray detection sensor and drain pan level sensor. In addition to triggering an alarm or warning (perhaps to close an open door), some sensors initiate control functions (such as stop the ice maker if the bucket is full). Magnetic switching devices such as reed switches and Hall effect sensors can provide some of these functions. Thermistors can provide the temperature sensing application in the refrigerator.
Smart/Connected Functions
Internet connectivity means that a smart refrigerator can sense the shortage of key items, perhaps with RFID devices on those products or a camera that sends product data to the cloud (and eventually the owner) after the door is opened and closed. With user confirmed authorization, the item(s) can be ordered online and automatically delivered by the user’s grocery store. Connectivity also means that temperature, humidity and other important sensed parameters can be monitored and uploaded to a cloud platform with real-time updates provided to the user.
With the cost of food getting more expensive every day, homeowners should be concerned with unnecessary spoilage that can cost a lot of money. An average homeowner can easily have over $300 of food in the refrigerator and if the freezer portion is included, it can easily exceed $1,000. This provides interesting possibilities for appliance and sensor designers to solve.
For example, LG Electronics offers a solution with its Insta View Refrigerator which needs the user to knock twice on the door (vibration sensor) to view the interior contents, without opening the door. This class of refrigerators has been recognized by the U.S. Environmental Protection Agency (EPA) for its potential to significantly reduce greenhouse gas emissions.
One sensor supplier offers smart home sensors for refrigerators to convert any existing refrigerator into an intelligent cost-effective system to provide better nutrition and enhanced health for the family. Sensors are programmed to sense the kind of products being stored using RFID scanning. It also determines when a food item should be replenished.
Additional sensors for a smart refrigerator include a temperature sensor, gas sensor and proximity sensor and load cells. The quality of vegetables can be checked through an app for improved human health. Using gas sensor(s), users are informed when vegetables and fruits are rotten. Sensors avoid outside air from polluting/reducing food quality by making sure the doors are closed.
To demonstrate how wide-spread smart refrigerator investigations are, Amazon has even received a patent for a refrigerator system that uses cameras and chemical sensors to detect spoiled food.
References
MEMS Sensors Support Efficiency Upgrades for Home Appliances (nmbtc.com)
US20190311598A1 – Scent-based spoilage sensing refrigerator – Google Patents
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