Smart gadgets are transforming our homes to become safer, more connected, and more fun to live in. Seeing a smart security camera spring into action at the slightest movement or sigh in satisfaction when your HVAC system turns the heating up just as it was starting to get cold are experiences that make the investment worthwhile. How do smart gadgets know when to activate themselves though?
The answer lies in sensors, devices which bridge the gap between the physical and the electronic world. Sensors measure a factor like temperature or movement and convert it into data smart devices can act on and understand. Once a threshold has been reached, sensors tell the smart device they’re part of or connected to that it’s OK to perform a specific action. That’s why your plants get watered only when the soil is dry enough and your home is always temperate regardless of the weather outside.
What Kinds of Smart Sensors Are There?
In this guide, you’ll learn all about different kinds of smart sensors and discover the working principles behind eight of the most widely used sensor types. We’ve also included the best choices for each so you have a reference if you want to upgrade your smart home with new gadgets that make use of them.
1. Motion Sensors
Motion sensors are the most widespread and versatile type of smart sensor. Most work by scanning a fixed area with an infrared beam and are triggered when a change in temperature is detected. Others use ultrasonic waves or microwaves to identify changes in the position of objects within range. Motion sensors are an integral part of smart security systems. They’re used as standalone devices you place on doors & windows or in a part of your home you wish to monitor. Motion sensors are also built into smart security cameras.
Earlier versions of smart motion sensors were prone to false positives. This was caused either by unreliable tracking methods like ultrasound and limited calibration options. Today’s models are more accurate due to improvements like adjustable range & sensitivity settings as well as ignoring the movements of your pets thanks to Pet Immunity.
Our Pick – Samsung SmartThings Motion Sensor
Samsung’s SmartThings is among the most popular smart home ecosystems. It supports hundreds of connected devices and allows you to orchestrate their behavior through scenes you create from a mobile app.
The SmartThings motion sensor is small and unobtrusive. You can easily mount it anywhere with two-sided tape, and a magnetic ball mount lets you make fine adjustments to the sensor’s position. It has a viewing angle of 120 degrees and detects motion 15 feet away. The sensor’s reset timer is fixed at 20 seconds, which ensures a quick response time.
Connectivity is this sensor’s most significant advantage. Thanks to SmartThings, it can be used as a trigger for light switches, devices plugged into smart plugs or even scenes that involve multiple smart gadgets. The SmartThings app will send you notifications when the sensor detects movement so you always know whether your home is safe or if your children are trying to access parts of the house they shouldn’t.
2. Temperature Sensors
Temperature sensors measure the ambient temperature by converting data on resistance into degrees Fahrenheit or Celsius. There’s a small piece of metal inside the sensor that electricity flows through when the sensor is active. The hotter the air around the sensor is, the more resistant the metal becomes. This resistance is then measured and interpreted by a microchip as a precise temperature value.
Smart temperature sensors have a wide range of application. They’re found in smart thermometers, weather stations, and thermostats. Their data can be gathered passively and viewed either on the spot or in a historical chart. However, the most practical use for thermal sensors is as a means of controlling your HVAC system.
Our Pick – Ecobee4 Smart Thermostat
Ecobee4 is a smart thermostat which regulates the temperature in your home thanks to data gathered in multiple rooms. It has a built-in temperature sensor and comes with a single portable one. Additional 2-packs are sold separately. The thermostat pools temperature and occupancy data from each sensor to direct your HVAC system to heat only the parts of your home which are in use. This leads to more efficient heating and considerable energy savings.
An Amazon Echo speaker is built into the ecobee4, meaning you have access to news, music, and voice commands through Alexa. Unlike its rival, the Nest Learning Thermostat, the Ecobee supports all major smart home ecosystems including HomeKit, Google Home, and SmartThings.
3. Light Sensors
Light sensors work on a principle similar to temperature sensors. They contain photo-sensitive resistors which change their conductivity based on how much light they receive. Less light means more resistance and vice versa. The resistors are connected to a circuit and cause changes in voltage. These are interpreted as changes in light levels and act as the sensor’s trigger.
Light sensors are used in smart security cameras to determine when the camera should switch to night vision mode. There are also standalone models that act as triggers for smart lights or security systems. Light sensors are effective burglar deterrents since you can use them to turn lights on automatically after dusk to create an illusion of someone being at home.
Our Pick – Aeotec Multisensor 6
As its name implies, the Multisensor picks up on much more than light levels. It also erasures humidity, UV levels, motion, temperature, and vibration. Its light sensor is particularly sensitive as it can distinguish light levels between 0 and 30,000 lux and track them through the Samsung SmartThings app. You can then use the readings to automate shades, lights, and more.
The UV sensor measures energy waves whose frequency is slightly higher than that of light which harm our health. The Multisensor 6 is able to track a room’s UV index and have SmartThings send you reports when it becomes too high. If you have smart shades, these can be lowered in response as well.
4. Leak Sensors
Leak sensors activate loud sirens when they come into contact with water. There are models which are attached directly to pipes as well as ones you place on the floor near a water source. Once wet, their probes change conductivity which alerts you of a leak. Some models use their legs to measure changes in conductivity and shouldn’t be placed on metal surfaces. Since early detection is vital, you’ll want to get a model that includes an extension cable which can reach under tight spaces.
Our Pick – iHome iSB02 Dual Leak Sensor
The iHome iSB02 is an affordable yet powerful leak sensor. It has both an internal probe and an extension cable, meaning it can detect leaks at two locations at once. Since they’re so cheap, buying one for the basement and each one of your bathrooms is a cost-effective way of preventing water damage.
The sensor has a 100dB alarm that will alert you or the neighbors when a leak happens. It also has a basic mobile app which will notify you of the leak just 10 seconds after it’s detected. The app supports IFTTT so you can plug washing machines, boilers, etc. into smart plugs which will turn them off when the leak is detected.
5. Air Quality Sensors
Unlike temperature or humidity, air quality is a less concrete metric that’s made up of multiple measurements. Air quality sensors measure concentrations of CO2, airborne particles, and volatile organic compounds (VOC) like methane and ammonia. The air in your home is then given a score. The lower the score, the less healthy the air is.
Air quality sensors often have humidity and temperature sensors as well to give a complete picture of your home’s atmosphere. They’re also present in air purifiers and can be paired with thermostats, air conditioners, or HVAC systems.
Our Pick – Foobot Indoor Air Quality Monitor
Foobot’s Air Quality Monitor is excellent at presenting its data in multiple layers. Anyone can get a basic idea on their home’s air quality by looking at the color of the monitor’s LED strip. It also responds quickly to sudden changes in air quality. Light your fireplace or start cooking dinner and the Foobot will notice instantly.
Its companion app offers more comprehensive information in the form of a general air quality score and detailed breakdowns for VOC, CO2, and airborne particle levels. Each statistic has a historical data section so you can look up how air quality fluctuates and what impact your actions have on it. Foobot directly supports the Nest Learning Thermostat and Amazon Alexa. Its readings can trigger an array of other smart devices through IFTTT too.
6. Smoke & Carbon Monoxide Detectors
There are two kinds of smoke detectors based on their working principle and which type of fire they’re good at detecting. Photoelectric detectors have an internal light source and a light sensor placed at a 90-degree angle from it. Ordinarily, the light would not come into contact with the sensor. When smoke enters the detector, it scatters the light beam, causing some of it to land on the sensor and activate it. Ionization sensors contain tiny pieces of radioactive material connected to a circuit. Smoke will cause the circuit to break and set off the alarm.
Ionization sensors are good at detecting fast-burning fires while photoelectric ones do better with smoky fires. Smart smoke detectors double as carbon monoxide detectors too. Their smarts can literally save your life – smart smoke detectors can automatically notify your local fire department, engage sprinklers to keep the fire from spreading, and take control of the lights so everyone realizes there’s an emergency faster.
Our Pick – Nest Protect
Nest’s Protect smoke alarm and carbon monoxide detector is a connected device that excels at detecting and notifying you of a fire or CO hazard. It is bigger than a traditional detector because of a motion-activated night light and multicolor LED ring which changes colors based on the situation and threat level. When a fire does happen, the Nest Protect will warn you by turning red, telling you to leave the house which eventually turns into a loud siren, and it will send a notification to your smartphone.
Nest Protect works well with other Nest products. The thermostat displays a fire or CO alarm and will shot off any active fans so the hazard doesn’t spread. A paired Nest IQ Camera will turn on and start recording an incident as it unfolds. Amazon Alexa is helpful too. Giving her voice commands lets you make a call or send an email to predefined contacts and control smart lights to signal an emergency.
7. Weather Sensors
Weather sensors gather data on temperature, humidity, barometric pressure, and other indicators which help you gauge the weather and plan ahead. Since they’re connected to your phone, you receive timely alerts when the weather changes. Smart weather sensors are also useful in gardening because they connect to smart irrigation systems and help regulate watering expenses.
Our Pick – Netatmo Weather Station
The Netatmo Weather Station consists of an indoor and an outdoor sensor. Both measure temperature & humidity. The outdoor sensor measures wind speed & direction while the indoor sensor keeps track of barometric pressure. The external sensor runs on batteries and its maximum communication range is 300 feet. A rain gauge is sold separately and alerts you to rainfall while keeping track of how much of it fell.
Netatmo’s Weather app provides an in-depth overview of all gathered weather data along with what the humidity and temperature feel like. Its readings are accessible from your phone’s widgets screen so you’re always in the know about local weather without needing to open the app. Netatmo Weather keeps detailed historical graphs on all measured stats and communicates with other smart devices.
8. Plant Sensors
Plant sensors measure everything plants need to thrive including light, temperature, soil moisture, and fertility. The last two require you to plunge the sensor’s pronged bottom part into the ground. Fertility is measured by the electrical output produced when the metal prongs come into contact with potassium and sodium ions in the soil. Moisture is determined by how much electricity the soil can transmit.
All of this info is of great help when you’re cultivating a garden or want to keep your houseplants from wilting. Smart plant sensors make their data available through mobile apps and web pages. They let you pick out the plants you’re monitoring and tell you how to recreate the ideal conditions for the plants’ development.
Our Pick – Parrot Flower Power
The Flower Power is a sprout-shaped plant sensor that keeps track of soil & outdoor temperature, humidity, fertility, and light levels. It’s easy to plant the Flower Power firmly into the ground and receive its data every time your phone is in Bluetooth range. The sensor is solidly built and suitable for both your garden and indoor flower pots.
The app allows you to personalize monitored plants by giving them names, attaching photos, and picking their species from an extensive list. You’ll receive push notifications whenever any of the readings is too high or too low and are given regular tips on plant care.