Sensori: the sensory system

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Training course - Chapter 3
Communication networks
Actuators and devices

ProAs a living organism, a domotic environment needs to feel the world around him and interacting with him, as well as having perception the profirst state. He must therefore be endowed with home automation sensors, or elements capable of providing, at any time, a timely reading of certain metrics (eg temperatures) or states (eg presence, opening gates etc.).

Sensor readings can be of direct type o indirect.

A temperature sensor provides a type reading direct, as its role is expressly to provide this reading: he questions himself, he answers. A more complex device designed to do something else but which, if questioned, provides some reading, therefore provides it in a way indirect. For example, a air conditioner it is designed to refresh the rooms but - if it is natively home automation - it can be interrogated to obtain the temperature of the environment in which it is located. IS, indirectly, a thermometer.

In addition to the sensors physical (as direct or indirect as they are), there are also some virtual considered as such as capable of gathering information procoming from external sources. For example, a website that provides real-time data on the atmospheric pressure of our neighborhood could be the data source for a virtual sensor in use in our home automation. Although we do not have a physical sensor, we could have a virtual one that provides us with the same features.

There is one great quality of different sensors, including:

  • drelative humidity, temperature, air quality (generally called "environmental");
  • di lumibrightness and noise;
  • of presence;
  • of opening gates (doors, finestre, dormers);
  • of vibration;
  • of air quality, atmospheric pressure, amount of rain, wind, radiation luminosa;
  • smoke, flooding;
  • cameras (IP CAM)

e many others. Those of course the most interesting for us are those home automation, because they can be integrated into our home automation solution. Also a mercury thermometer for medical use it's a sensor, but it will never be useful in building a home automation system. If you can, let us know.

Sensori of humidity, temperature, air quality

The most common sensors are those of humidity and temperature. These components respond, when interrogated, by providing instantaneous readings of relative humidity and temperature, usually expressed as percentages and in degrees centigrade or fahrenheit. This type of sensor is usually useful for the automatic management of heating / cooling systems.

Some examples:

Il Xiaomi sensor is a component capable of providing instantaneous readings of relative humidity and temperature and barometric pressure of the environment in which it is installed, while the NETATMO Weather Station it is a real e profirst mini-meteorological station equipped with an external probe: this device can therefore provide relative humidity and temperature both in the environment in which it is positioned and in which the external probe is positioned.

A digital home automation thermostat it is usually also a sensor indirect of humidity / temperature. An example:

Tado° V3 intelligent thermostat
Tado° V3 intelligent thermostat

This device (in this example, the "Tado° V3 Smart Thermostat") Serves to drive a heating system, but it is also a indirect sensor, as it is able to provide relative humidity and temperature readings to our home automation system.

Sensori luminosiness and noise

The sensors of lumiusually nosiness provide instant reading of the number of luxury of an environment. These components are useful for automating the switching on or off of the systems of thelumination.
The noise sensors, however, they usually provide instant reading of the number of decibels present in the environment in which they are positioned.

A device that integrates both these types of sensors is, for example, the Broadlink A1 e-Air.

Sensori of presence

These sensors serve to detect movement (hence the presence) of a warm body in a volume of air. They are in fact also called "volumetric" and are an essential part, usually, in anti-intrusion systems. Although there are various techniques for determining presence, one of the most classic direct sensors is that a infrared, like this:

Sensorand infrared presence

However, there are also virtual presence sensors. For example, a surveillance camera can detect presence if the prosoftware, through real-time image processing which it takes up again, is able to distinguish a variation in the image such as to be considered movement, and therefore presence.

Sensorthe opening points (doors, finestkings, dormers)

Although - as in the case of presence sensors - there are more technologies to monitor the opening of a passage (it is a door, a finestra, a bascule etc.), the most typical is that with magnets.

In essence, the magnetic sensor it is positioned on one of the two wings of the gate to be monitored, while the real magnet e is positioned on the opposite sash proprio. The allontanamento (and therefore opening the gap) of the two components triggers a signal to be interpreted by home automation as an opening (and be treated accordingly). An example, among the thousand on the market:

Sensorand opening gap

there more complex sensors which are not limited to proof an opening signal, but they can also be interrogated and therefore instantly provide their status as "open" or "closed" (those described above only indicate the event of "opening", are therefore defined "stateless", Without status).

Sensori of vibration

An example of this type of sensor is the Aqara: it is a component able not only to detect the magnitude of a vibration, but also its relative position based on an instantaneous reading of the three axes.

Aqara vibration sensor
the Aqara vibration sensor.

This sensor is usually used to monitor gates, glass surfaces (finestre) but also safes and more.

Sensori of air quality, amount of rain, wind, radiation luminosa

There are sensors that can sense the meteorological reality of a given environment.
I quality sensors of the air are components capable of assessing concentrations of harmful gases (eg carbon dioxide) as well as the degree of pollutionnamefrom microparticles (PMx). They are useful for assessing the quality of the breathed air.

The sensors of quality of rain, wind, radiation luminosa and other readings are typically sensors dedicated to meteorological monitoring. These components can be purchased separately or in the form of real proprie weather stations:

The first, the NETATMO Weather Station is the extended version of the one described earlier in this article; the second is the DAVIS VANTAGE PRO-2. These weather stations prothey are providing very accurate data and are particularly useful in case we want to domotize outdoor environments (gardens with irrigation and thelumiautomatic national tents, awnings, etc.).

Such sensors can sometimes be virtualized: adopting in the profirst home automation a personal automation center, or HUB, it is possible to configure virtual sensors that record data from websites. An example is that of "wunderground" plugin for Homebridge (of the latter, and more, we will talk later).

Sensori smoke, flood

For accident prevention such as fires and floods, there are sensors appositi. For example:

The first is the NEST Protect 2, the second a smoke sensor Xiaomi / Aqara; the third, the D-Link DCH-S160, an flood sensor.

Cameras (IP CAM)

With the evolution and the miniaturization of image sensors, in recent years there has been the advent of generations of cameras useful for environment security monitoring of always superior quality and with the ever-lower cost (as well as the increasingly pleasing and modern features).
Two examples:

The first is the D-Link DCS-5000L, IP Cam from inside, motorized, while the second is the Foscam FI9900P, fixed camera, from outside. Both are - as all IP CAMs are now - Wi-Fi and equipped with night vision. As explained above (presence sensors section), certain IP Cams can be used - via software - as true e profirst presence detection sensors.

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