Sense Home Energy Monitor
Sense Electrical Signals

A Device Discovery Mystery

Can you figure out what the mystery electrical signature is? Hint: we were celebrating a birthday.

It’s not all work for the data science team at Sense. We also like to have fun! Rhoda, our Director of Marketing and Business Development, had her birthday a couple of weeks ago. To celebrate, the team decided to surprise her, the Sense way!

During one of our weekly “Lunch & Learn” gatherings, we snuck these two plots into our slides. Figure 1 shows an activity lasting about 45 minutes, and Figure 2 is a zoom-in on the first plot at around 7pm.

Can you guess what is going on?

Figure 1- A snippet of activity for a bit less than 45 minutes between 6:45-7:30pm!
Figure 2- A zoom in on the activity at 7pm.

This one is tricky so a few hints are in order. First, note that the entire activity covers about 45 minutes, and according to the timeline, it is happening in the evening between 6:45 and 7:30pm. The appliances of interest are:

  1. A cycling heat.
  2. A motor (see Figure 2).

First, let’s have a look at the cycling heat. The heat element consumes around 400W when on, and the duration of its first instance is around 500 seconds, which is longer than those of the cycling instances. This suggests a heating device that stays on to reach a certain temperature and then cycles over time to maintain that temperature. There are a few devices that exhibit such behavior. Can you think of any? Here are a few: coffee makers, space heaters, ovens, etc.

Before we reveal the heat appliance, let’s turn our attention to the motor. The motor is on for 19 seconds, consumes around 100W, and does not cycle or have any form of repetitive pattern. There are quite a few motors that behave similarly: vacuum cleaners, garbage disposals, a variety of kitchen appliances such as mixers and blenders, etc.

To solve this mystery, one needs some appliance specific information, and a little bit of common sense (excuse the pun). The activity is limited in duration (and recall the whole birthday celebration!) Also, using appliance knowledge regarding power consumption and duty cycles, we can eliminate coffee makers and space heaters for the heat appliance. Similarly, garbage disposals tend to have a different onset and vacuum cleaners consume more power. It seems more and more likely that this involves some form of cooking or baking and the heat element belongs to an oven, which is first preheated, then left on for another 30 minutes. (One more chance for the reader to guess what is going on!)

At this point in the presentation, a lot of the team members yelled: “Cake!” and that was the correct guess. The motor is in fact the mixer used to beat the eggs. A couple of tips for the baking enthusiast. First, this was a flourless cake, and to keep it fluffy, we don’t overbeat the eggs, hence the short motor duration. Second, to clean the beaters, we turn the mixer back on briefly and slowly lift it so it does not touch the batter anymore. Any leftover batter on the beaters will fall back into the bowl and the beaters are easier to clean. This actually explains the second very brief occurrence of the same motor right after the first one.

Hope you enjoyed our brief baking tutorial. Happy Sensing!