One hertz is one cycle per second, meaning repeating cycle as an event. For example, hertz is applied physics measuring the number of times for a second wave (either acoustic or electromagnetic) is repeated or can be applied, among other uses, to ocean waves that reach the Beach vibrations per second or a solid. The quantity that measures the frequency hertz is called,in this regard, the inverse of the period. One hertz is an oscillation frequency of suffering a particle over a period of one second.

The Wifi technology is a wireless communication mechanism between devices. This technology allows you to connect devices such as computers, laptops, mobile etc... to the Internet or communicate with the devices themselves.

Applications can be several, among the most common are the access points, ideal for giving and sharing a connection signal to multiple devices. It is the typical configuration of a home user.
Repeater, ideal to repeat and amplify weak signal.

The power and range between devices basically depends on the antenna and its hardware.

The wireless signals work under a unified standard regulations, the standard that is based on the IEEE 802.11. These include IEEE 802.11b, IEEE 802.11g and IEEE 802.11n working at 11 Mbit/s, 54 Mbit/s and 300 Mbit/s, respectively.
Being any device with a standardized protocol such technology can connect to another using the same technology, making it a kind of universal connection.

The wireless networks are characterized by the ease and convenience of making connections in infrastructure, since it is not necessary to perform network cable installations.
it also allows connecting a lot of devices to a single node.

There are several ways to connect electronic devices to each other; cables, infrared, etc. Bluetooth technology is one of them and enabling wireless transmission of voice and/or data between devices by radio frequency.
It is a technology of radio waves at short range (2.4 GHz) whose objective is the communication between devices such as computers, smartphones, tablets, printers, headsets and other dispositives hand.
Bluetooth is called the communication protocol specifically designed for low-power devices. These devices can be classified according to their transmission power:
- Class 1: 100 mW, maximum range approximately 100 meters.
- Class 2: 2.5 mW, approximate maximum range between 5 and 10 meters.
- Class 3: 1 mW, maximum range approximately 1 meter.

We can also classify this technology by standard. All these versions have backward compatibility, ie, it allows the latest standard is compatible with all previous versions.

- Version 1.2: 1 Mbit/s
- Version 2.0 + EDR: 3 Mbit/s
- Version 3.0 + HS: 24 Mbit/s
- Version 4.0: 24 Mbit/s

Within the detection systems we can find different types according to their operation, among them the most common:

1. Infrared sensors
2. Vibration sensors.
3. Photoelectric sensors.
4. Ultrasound sensors.
5. Acoustic sensors

Each type of sensor uses different detection methods and each one is recommended according to the situation.

1. Sensors by infraRrojos, are one of the most used types, thanks to its reliable operation and installation, since we can find this type of wired and wireless sensors.
   The infrared sensor has a phototransistor capable of detecting the infrared electromagnetic radiation emitted by a body, this type of radiation is not visible by the human eye. A change of radiation in its perimeter will activate the relay and proceed to send ato alarm signal.
   Within these, there are two models, passive infrared sensor, which only has a phototransistor and assets, which have an emitter and a receiver.
2. Vibration sensors are used mostly in security systems, such as window sensors. car alarms etc.
   Its operation is based on an accelerometer, through a piezoelectric sensor. This type of sensorDue to its construction material it allows to detect changes and pressure when emitting an electric charge.
3. Photoelectric sensors, these are the sensors that use photoelectric rays, normally a transmitter and a receiver are used, they are commonly used in automatic door systems, elevator doors, production chains, etc.
4. The ultrasonic sensors are those that emit an acoustic signalabout 30 kHz, a signal that is not appreciated by humans. This signal or wave propagates through space, walls, objects, doors, etc. once the signal has spread the sensor is activated and any change will trigger the sensor.
   These types of sensors are also used in devices that require measuring distances and detecting objects.
5. Acoustic sensors, are those that can detect the signal emitted by anyobject and are able to detect the pressures that the acoustic waves emit, such as the noise of the crystals when breaking a window.

Arduino is defined as a combined system between hardware and software, which allows users with or without programming knowledge to create projects from scratch. Thanks to its low cost and its wide range of accessories, it has become one of the most appreciated devices by the creative community or called makers (creators).

Within the Arduino range we can find different devices, which will allow us to easily create projects that perform different functions. Its open source GNU free access is essential in the maker community, which allows its creator to develop almost any prototype he can think of.

Arduino was created with the aim of reducing and lowering the material costs needed by interactive design students from Ivrea, Italy, since the devices they used previously were very expensive. This new Arduino project reduced the cost of the material each student needed and eventually became a commercial product as we know it today.

These small plates consist of a SRAM memory, with its own flash storage system (EEPROM), microcontrollers and a microprocessor, currently we can find different processors for the most current models, such as processors:

- 8-bit Atmel AVR
- 32-bit ARM Cortex-M0+
- 32-bit ARM CortexM3
- Intel Quark (x86) 32-bit

Arduino has an open source programming software called the Arduino IDE, with which anyone can create the basis of a new project. Both software and hardware are compatible with Windows, MacOS, and Linux operating systems. Its programming only requires a USB connection to the PC and the free programming software.

Among the different devices we can find the main Arduino board, the nerve center of any project, among which we can find:

- Arduino Uno R3
- Arduino Leonardo
-Arduino 101
- Arduino Explore
-Arduino Zero
- Arduino Mega 2560
-Arduino Due
-ArduinoMicro
- Arduino Nano
- Arduino MXR 2 UNO Adapter
- Arduino MKR Zero
- Arduino Yun
- Arduino Ethernet among others



In order to expand its functionality, we have a wide range of shields or modules that allow you to expand its functionality, such as screens, Wi-Fi modules, etc. these can be attached to the Arduino board itself, thus allowing it to read inputs and send data outputs. Among some shields we can find:

- Xbee wireless modules
- USB ports
- Sensors
- Breadboard
- Card readers
- WiFi connection
- Motors or servos
- Ethernet connection
- GPS module
- GSM module
- RS232 module
- Relays
- LCD screens
- Sound and DMX

Among some examples that we can create with Arduino and its external components we can find clocks, scales, alarms, automated irrigation systems, a battery tester, control of mechanical arms and much more.

Thanks to its large community of makers, we can find hundreds of projects to carry out on the net, ideal for delving into the world of electronics and programming, whether at an educational, professional or domestic level.