The smart home ecosystem has dozens of sensors and actuators responsible for safety, automation of household appliances, lighting and climate control. New users are tempted to decorate their apartments with sensors like a Christmas tree with toys. The purpose of the article is to highlight the “basic composition” and consider aspects of its application.

What are sensors?

Sensors are designed to convert a physical quantity into an electrical signal. As a result, we can measure this quantity quantitatively (temperature, humidity) or record its change (recognize movement). The following sensors are freely available from most major market players:

• motion/presence;
• windows/doors opening;
• lighting;
• environmental parameters;
• leaks;
• smoke;
• glass breakage;
• gas leakage;
• air quality monitoring;
• video cameras.

What are actuators

Actuators are defined as actuators that generate signals to influence other elements of the smart home. This is a direct effect either through a signal (button) or through an actuator (electronic valve). An actuator can also be a household appliance controlled by a smartphone, such as a smart air conditioner. In this case it is also possible to control an ordinary air conditioner, but already with a smart remote control, which will become an intermediary between the device and a smartphone. The task in this case is the same, but the variants of solution are different. A separate class of devices are intelligent light devices. About the smart light is described in detail in a recent article.

A list of smart actuators:

• multifunctional button;
• switch;
• relay;
• socket;
• lighting devices (lamp, base, lamp, LED strip);
• home appliances (refrigerator, air conditioner, coffee maker, etc.)
• infrared remote control;
• electronic valve;
• actuator for curtains.

Let’s take a closer look at what devices are the most necessary to build a basic home automation system. There are several variants of ready-made starter kits from the manufacturer.

Each of them does not fully cover the minimum needs, being more focused on either safety or convenience. Let’s put together a kit that satisfies both.

Motion sensors.

The old-timers of the smart home, known since the days of the first remote-controlled security systems. The most common are passive infrared sensors (PIR-sensors). They contain sensitive pyroelectric element detecting change of infrared radiation when an object moves in control zone. This zone has a radius of 4-8 meters that allows a room to be covered by a single sensor. The standard location is the top corner of the wall opposite the entrance to the room.

Motion sensors are so common that they are, among other things, part of other devices, such as light bulbs. These sensors are most commonly used in lighting scenarios: automatically turning lights on and off based on activity in the room. In terms of integration with the rest of the smart home system, there are no problems, as there are many devices with different interfaces. These sensors, which have a large number of application scenarios, are an ironclad part of the foundation of a smart home. 

Window/Door Opening Sensors

Door and window opening sensors consist of two parts – a reed switch and a magnet. They are mounted on the door frame/window frame and sash, and when they are disconnected, the sensor is triggered.

The simple and durable design has long established these sensors as an integral part of security systems. They are also widely used in smart light scenarios. It is difficult to imagine a smart home without these devices.

Water leakage sensors

Most of them work due to the difference in electrical conductivity between air and water. When water hits one of the contacts located on the bottom of the device, a signal is generated. Sensors are installed in the vicinity of likely sources of leaks: under the hose of the washing machine, next to risers, sinks, heating radiator. Also, if there is a slight slope, the lowest point on the level will be good for installation.

To ensure that the system is not only signaled the incident, but also to prevent its consequences, use devices that cut off the water supply. Usually it is a special electronic valve, but there are original embodiments of Chinese engineering in the form of an electric actuator for the handle of the ball valve.

In terms of integration into the smart home, this system is not always convenient, because it comes as an independent set. The proprietary controller will not be friends with the general gateway and there are only variants with work through a smart socket or support of the voice assistant. Therefore, only sensors go into the main set, and actuators go into the backup set.

Smoke detectors

Similar in principle to the standard fire detectors, which are mandatorily installed in new buildings. When smoke particles enter the sensor’s photodetector field, the intensity of radiation changes and is triggered. A siren is activated, and if the detector is addressable, it sends a signal to the fire alarm panel. There is no point in having an additional smoke detector if such equipment is available. Otherwise, a sensor is mandatory.

Gas leak detectors

Respond to an increase in the concentration of household gas in the air. Makes sense to use if you have a gas stove and (or) a column. Must be installed in proximity to gas appliances.

Temperature and humidity sensors

Controlling environmental parameters is another important function of a smart home. A good climate in the house is good for the health of the family, pets and indoor plants. Temperature and humidity measurements are increasingly available within a single device. It is impossible to imagine a smart home without these sensors. Atmospheric pressure is added to them, but this indicator cannot be influenced, so it is of a reference nature. And the two main parameters can and should be controlled.

For this purpose, we use air conditioners and humidifiers. These are already more expensive devices compared to sensors, and you can consider buying them in the long term. They also come in smart and help to fully automate the process of adjusting the weather in the house. If the temperature or humidity goes outside of the preset thresholds, the appropriate device will turn on. It will run until the desired values are reached.  

Deciding on actuators

As basic actuators, we suggest considering smart outlets, switches, buttons and lamps.

Some smart sockets not only allow you to control the state of lights and appliances, but also to keep track of the power consumption. Switches and buttons are also useful for implementing lighting scenarios and turning appliances on/off.

Another handy thing is a smart infrared remote control. It can replace all other remotes for TV, air conditioner, etc. Imagine that now you will not have to look for them at all!

Gateway

All sets of a smart house have one obligatory element – control unit, also known as gateway or the control center. It is the “brain” of the system which is responsible for control of all devices of the smart house and execution of scenarios of automation. It receives data from sensors and transmits it to the server of the manufacturer for processing. Thanks to this, you can track this data in a convenient format – in an application on your mobile device, from where you can send commands to the executive devices in a couple of clicks.

The gateways support various wireless data transfer protocols required for data exchange with all system components: Wi-Fi, Bluetooth, ZigBee, Z-Wave, RF. If there are a lot of devices, they are combined into groups, for which hubs are used.

There are several cloud smart home systems that do not require a control unit. These platforms are Apple HomeKit, Google Home. In this case, the command from the application flies straight into the cloud, where it is processed with the help of a library of functions from the manufacturer of a particular device.

Smartphone apps

Each manufacturer has its own smart home control app. They all know how to display a list of devices, sensor readings, and send commands. An example of how to set up Mi Home, and Rubetek. In terms of third-party vendor support, Mi Home is well established.

The main function of the apps is to create automation scenarios to achieve specified conditions. They are the main “chip” of a smart home – automatic execution of actions without human involvement. There is another “chip”, which will be discussed below. 

Be heard 

Voice control is tightly integrated into the smart home. The three cloud platform developers discussed above are all developing their own voice assistants: Siri, Alexa and Google Home. Voice control takes the smart home system to a whole other level, but it also has some drawbacks.

Compared to smart device manufacturers’ apps, voice assistants have more modest capabilities to support devices and their functions. The list of devices that can be paired with Mi Home is much broader. In addition, Google Home does not yet accept all the commands for the devices available in the app. Nevertheless, the list will expand, and the convenience of voice control will offset these imperfections.

Next, you need to select a manufacturer and on the appropriate tab to merge accounts, for example, with Mi Home. The devices will then be displayed with available voice commands.

You can manage individual devices and merge them into groups. For a more comfortable communication with Alice, use a smart speaker.

The smart home team

Let’s summarize in a selection of the minimum set of smart devices:

• motion sensor;
• door opening sensor;
• water leakage sensor;
• socket;
• switch;
• button;
• IR remote;
• lamp;
• gateway.

If there is not yet a clear understanding of what scenarios will be used, it is possible to take all devices in one instance. One of the advantages of the system is scalability. Most of the sensors are battery operated and attached to 3M scotch tape, so adding such items is not difficult. Don’t forget to read about hardware and app or voice assistant compatibility beforehand. If you’re planning an installation during the renovation phase, consider smart relay options and identify power outlets for smart home devices beforehand.

Adding sensors and actuators to the system from all manufacturers is as simple as possible and consists of a few steps:

• Connect the device to the power supply (if required).
• Initiate the addition of the device in the application. Then proceed according to the instructions of the application. Usually it is enough to press the button on the device several times.
• After pairing with the device, a list of available functions appears in the application. You can use them independently or include them in automation scenarios together with other elements of the smart home. 

A smart home is a separate engineering system that deserves a thoughtful design approach. In this case, smart devices will become your trusted home helpers.