Pocketnow Smart Home: selecting your sensors


“A smart home is only as intelligent as the sensors supplying data.”

Most homes today only have a few devices to monitor environmental variables, but you already may have a few more than you think. You have a thermostat which controls your heating and cooling system. Your refrigerator/freezer has a couple thermostats inside to tell it when to turn on and off to make sure your food doesn’t go bad – it’s even got a smart switch that turns the little light off when you close the door. Even your sprinkler system could be considered a “smart” device of sorts. Of course, these aren’t the types of things you think of when you hear “smart home”, but they do lay the foundation for what we’re going to talk about today: smart home sensors.

Types of Smart Home Sensors

sensor-door-windowThe easiest type of sensor to visualize is a magnetic switch. Installing one of these puppies on your door or window is easy enough. When the door or window opens or closes, the two components are separated or brought together, which opens or closes the circuit. The electronics in the other half of the sensor send a signal to your hub, identifying itself and the event that has just happened.

Not too dissimilar from the window/door sensor is the tilt sensor. Instead of opening or closing a circuit with a magnet, tilt sensors generally use gravity. When the sensor changes from a horizontal to a vertical orientation (or vice versa), a signal is sent. These are typically used on garage doors to indicate whether the door is in the “up” (horizontal) or “down” (vertical) position.

sensor-floodA sensor that is often used in home security systems is called a “glass break” sensor. These little devices are basically just a microphone and microchip that “listen” for the sound of glass breaking. When that particular type of waveform is observed, the sensor will send a signal to your smart home hub. Generally this will be programmed to sound an alarm, send an email, or possibly even notify a security monitoring service.

A sensor that would have helped me a few weeks ago is called a “flood sensor”. This type of sensor usually has two metal prongs and sits on the floor. If there is a leak (or a flood), the water bridges the two prongs, closing the circuit and triggering a signal to be sent to your hub. In my case, I had a sewage lift station pump fail, causing water to back up into the basement. Luckily, a friend heard the problem (which occurred very early on New Year’s Day) and we were able to stop the inflow of more water before things got really bad.  If I’d had this simple, relatively inexpensive little sensor, I could have (a) been notified earlier, or (b) had smart home rules set up to automate the corrective action for me.

Temperature and humidity sensors often come bundled into the same unit, but you can also find that as separate, discreet components as well. Use of these sensors can help you monitor temperatures so you can be notified or take action when temperatures reach a certain trigger point (usually close to freezing, or at some relatively high temperature). When configured with smart hub rules, these sensors can help keep pipes from freezing, food from spoiling, and can even open doors for pets, and so much more.

sensor-motionMotion sensors are very commonly used to let you know when people are approaching a door, or occupying a space. When motion is detected, a signal is sent to your smart home hub, which can fire rules to turn lights on, send an alert, or simply log the event.

Nest is leading the way with another few types of environmental sensors: learning thermostats and smoke+CO2 detectors. Nest is in a category all its own (for better and for worse), so I’ll cover all that in an upcoming installment. In the meantime, you can install a non-Nest smart thermostat to monitor temperatures in your home, and even smoke, CO2, radon, and other environmental factors. These devices usually take action on their own (turning your HVAC system on or off, or sounding an alarm, but they can also notify your smart home hub, allowing you to be notified or take action based on their information.

Novelty Sensors

smart-egg-traySo far, all the sensors I’ve mentioned are pretty practical. There are, however, some sensors that are much more whimsical – though every bit as cool.

The Quirky Egg Minder is a smart egg tray that will notify you when your eggs are getting old, and when you need to pick up some more. Of course, for guys like me, this is completely silly. If I need more eggs, I just walk out by the garage, open the hen house, and grab a couple. For city-dwellers and suburbanites that haven’t made the leap to backyard chickens yet, this type of device may not be such a silly idea – especially if you don’t eat eggs very often.sensor-propane-tank

Another idea that sounds silly at first is the Refuel Smart Propane Tank Gauge. This little gadget sits under your propane tank and tells you when the tank is getting a little light – in other words: when you need to refill the tank with more propane. Again, guys like me won’t see much use in this (I’ve got a 1,000 gallon tank buried in my yard, not a wimpy 20lb tank like this sensor works with), but those with backyard barbecues, or even campers could see some real benefits from a sensor like this.

Other Sensors

For the most part, the sensors mentioned here will cover about 90% of what you want to set up your smart home. I’m still looking for a ZigBee or Z-Wave driveway sensor that will send a signal to my Almond+ when someone comes down my lane, otherwise, it’s just a matter of getting everything installed.

What are some other sensors that you’ve seen around (or that you’d like to see)? Head down to the comments and let me know!

Make sure you tune in next week when I’ll cover devices for your smart home: light bulbs, power outlets, switches, alarms, and more!

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About The Author
Joe Levi
Joe graduated from Weber State University with two degrees in Information Systems and Technologies. He has carried mobile devices with him for more than a decade, including Apple's Newton, Microsoft's Handheld and Palm Sized PCs, and is Pocketnow's "Android Guy". By day you'll find Joe coding web pages, tweaking for SEO, and leveraging social media to spread the word. By night you'll probably find him writing technology and "prepping" articles, as well as shooting video. Read more about Joe Levi here.