Dishwasher Detection: A Look Inside Your Dishwasher

We’ve learned a lot about dishwashers while developing Sense. Our resident dishwasher expert shares some facts you may not have known about dishwashers, and about how we sense them.

Dishwashers have become so pervasive in households that most people would not survive the day without running them. We all know the spiel: dirty dishes go in, we hear water slushing and spraying, then ta-dah! clean dishes come out. The data science team at Sense decided to dig a little deeper into what's really happening in a dishwasher. Here are some under-the-hood features you did not know about your dishwasher.

Basic Dishwasher Design

The basic design of a dishwasher has not changed that much since first invented by Josephine Cochrane in 1886. Nowadays, most dishwashers consist of two main building blocks:

  1. A motor that pumps water into the water jets causing them to rotate and spray water on the dirty dishes. The rotating water jets are the reason one should not overfill the dishwasher. If the jets are blocked or too covered, they will not rotate efficiently and rinse all the content of the dishwasher. The same motor could be used to drain the water out of the dishwasher once rinsing is done.
  2. A heating element is typically located at the base of the dishwasher. This unit heats up water to much higher temperatures than is typically possible during hand-washing. In fact the heating elements heats up the water to such high temperatures that one could consider steam cooking in the dishwasher! Here's a recipe for the curious.

A segment of a typical time signature for a dishwasher run is illustrated below.

cropped typical dishwasher signal

Consistent Motor-heat Timing 

There is a very distinct time relationship between the dishwasher pump motor and the heating element. This time correlation could be different from one dishwasher brand to another, but it is pretty consistent across multiple runs of the same brand. This time relationship is illustrated in the figure below.

Brand-specific Motor Sequence

Some dishwasher brands have such a specific circulation pump motor sequence, that one would be able to distinguish a brand from another from this time signature alone. The figure below illustrates part of the motor signature for a particular dishwasher brand.

This sample of dishwasher features illustrates the many challenges we face when modeling and automatically detecting an appliance. Questions our team asks are: how is a motor different from a heat element? what makes a motor part of an appliance? how do we model the relationship between various parts of a device? Each of these questions brings with it a set of interesting problems and discoveries.

The variable features demonstrated above are also typical of the interesting patterns we see when investigating different appliances. Such variability introduces complexities in our disaggregation models, but also provides interesting cues that can be exploited to achieve high accuracy.