How do sensors improve home appliances? Part 1

Today’s home appliances are increasingly connected for remote monitoring and control and smarter due, in part, to numerous sensors. The sensors help even lower-end appliances implement their basic functions and, more importantly, enable smarter, top-end appliances. While sensors provide these capabilities for several home appliances, this two-part series will describe sensing functions for large appliances in the laundry room and in the kitchen.

In the laundry room, basic functions can be designed in using established magnetic sensing techniques such as reed switches and Hall effect devices.

To prevent the wash cycle from starting with water pumping into the drum, top-load washing machines need to sense that the lid is closed. A contactless reed switch and a magnet can provide this sensing as well as sensing for different water levels depending on the various wash cycles. Dial position, drum speed for many different cycles, and detergent level sensing can be implemented with Hall effect sensors.

Basic washing machine functions can be implemented with established sensing techniques. Figure source: littelfuse_position_and_level_sensing_in_washing_machine_application_note.pdf.pdf

Smart/connected functions
In addition to connectivity, smart appliances have reduced power consumption and improved efficiency as well as increased robustness thanks to different types of sensors.

For example, a negative temperature coefficient (NTC) temperature sensing element can measure the air or water temperature and provide that information to the control unit of a washing machine or clothes dryer to regulate heating elements and minimize power consumption.

A low differential microelectromechanical systems (MEMS) pressure sensor can be used in a clothes dryer to notify users when lint builds up in different parts of the machine and decreases drying efficiency. Inertial MEMS sensors can provide an out-of-balance indication that is especially important at higher speeds in the washing machine such as the spin cycle.

In the washing machine, force sensors can measure the payload weight at the beginning of the wash cycle.

In the dryer, a humidity sensor can monitor process humidity and stop the dryer when the clothes are dry instead of running longer and consuming more power.

With a dirt sensor, a washing machine can detect exactly how dirty the clothes are when the machine nears the end of its cycle. In one modern machine, if there are still marks or stains on the clothing, the washer will automatically dispense more detergent and respond to make sure the laundry comes out clean.

In another approach, a photoelectric sensor can be used for detecting draining water quality and the appropriate algorithms can detect if the cleaning process has sufficiently performed its function or if additional cycles are required.

Sensing when clothes are dry and do not need to fully complete a cycle can save on power consumption for the homeowner.

In both washing machines and dryers, touch screens with controls use either capacitive or resistive touch sensors to provide input to the machine and perform internet searches as well.  With their internet connectivity, smart washers and dryers can be set up to send a notification to the user’s phone when they have completed their cycle.

Part two of this blog will discuss sensing in a major kitchen appliance: refrigerators.

References

littelfuse_position_and_level_sensing_in_washing_machine_application_note.pdf.pdf
Most In-Demand Sensors For Manufacturing Of Household Devices (911electronic.com)
MEMS Sensors Support Efficiency Upgrades for Home Appliances (nmbtc.com)
Samsung’s new washers detect how dirty your clothes are and adjust automatically, here’s how | Top Ten Reviews
CN85204208U – Photoelectric detecting controller for washing machine – Google Patents