Sensor Helps Scrub Away That Troublesome Lasagna

R. Winn HardinLance Thompson, Honeywell Micro Switch, Freeport, Ill. 61032; (815) 235-5981.

Whether it's baked-on lasagna or simple chicken soup, Maytag is making use of advanced sensors and technologies to offer dishwasher owners reductions in energy use, operational costs, water consumption and washing time.
This "smart" dishwasher, called Intellisense, relies on a set of sensors and fuzzy logic to continuously monitor the harsh environment inside the dishwasher and direct the appliance to save time, water and energy without compromising the quality of the wash.
Typical dishwashers waste energy and water because they depend on fixed time-based cycles to clean dishes, regardless of how soiled the dishes are or the type or amount of detergent used. They are blind, overwashing dishes and wasting water, energy and time. But thanks to a wash process sensor from Honeywell's Micro Switch Div., Maytag's Intellisense has the power to sense conditions during the wash cycle and adjust accordingly.
Honeywell's sensor subassembly integrates four sensors into a single housing. The sensors continuously monitor turbidity, conductivity, temperature and lower wash arm rotation. The turbidity sensor consists of a visible red light-emitting diode, a transmissive detector and a scattered detector. It reads the water's turbidity, or opaqueness, by measuring the ratio of scattered to transmitted detector outputs. A patented gain circuit drives the diode and reduces the impact of signal-degrading effects such as source intensity, package yellowing or filming. A conductivity sensor monitors a low-amplitude AC signal, while a thermistor and magnetoresistive position sensor keep track of water temperature and lower arm rotation, respectively.
The Intellisense's controller uses these sensor outputs, in conjunction with other information such as frequency of door openings and time between loads -- along with fuzzy logic algorithms to tell the dishwasher how long a given cycle should run, whether or not to skip some cycles and how much to heat the water.