Webcam

A webcam is a digital video and photo camera connected to a computer. It is used to transmit images over the Internet.

You can purchase webcams separately, but they are already built into laptops and smartphones.

The camera connects to a computer and delivers images to a web server by request, either continuously or at intervals. Some cameras with special software work independently as a web server and send images via e-mail.

Security webcams can be equipped with motion detectors, external sensors, night vision sensors, etc.

Device

The main part of a webcam is the sensor. It is a semiconductor chip that consists of millions of light-sensitive squares. These squares are called pixels.

The camera also has an analog-to-digital converter and a microprocessor.

How it works

1 - Lens

2 - Optical filter

3 - Sensor

4 - analog-to-digital converter

5 - Compression block

6 - Central processor

7 - Flash memory

8 - RAM

9 - Internet

10 - COM port

11 - Input/output unit

1. The light sensor in the cameras is used to capture the light image and transmit it to the microprocessor. This sensor converts the captured light into electrical signals.
2. The central microprocessor transmits the signal to the analog-to-digital converter. It converts the analog image into a digital one, in other words, into a code of zeros and ones.
3. The compression units compress the digital signal into MPEG format files.
4. The information is transmitted to a computer via a USB interface, then to the Internet.

Main parameters

Resolution

It means the number of pixels vertically and horizontally on the image sensor. The more pixels, the higher the image quality is.

FPS

This is the number (or frequency) of frames per second that the camera can process. Budget cameras have frames per second of about 24. A good fps rate is between 50 and 60 frames per second.

Computer Mouse

A computer mouse is an input device for entering information into a computer. Computer mice, like keyboards, are available as wired and wireless. 

A wired and wireless mouse adapter plugs into the USB port.

PS/2 port, which connects the mouse and keyboard, is obsolete. It is rarely found in modern computers.

Principle of operation

The device tracks its movement on the working surface with a movement sensor and transmits the movement information to the computer's operating system. The operating system makes the cursor move. The keys on the mouse drive a context menu, activate a specified feature, or scroll through web pages.

Keys

1 – The right button. It reveals a context (additional) menu that provides additional actions.

2 - Scroll Wheel. It allows you to scroll up or down files of different formats.

3 - The left button. It is used to open documents and launch programs.

4 and 5 - Auxiliary buttons. The mouse may have auxiliary (side) buttons for convenient work and games.

Types

Optical Laser Mouse

This mouse uses a type of optical sensor that applies a semiconductor laser. The laser emits light in the infrared range. The sensor in the mouse picks up the wavelength of the reflected light, which varies depending on the surface.

Optical LED Mouse

This mouse has an optical sensor (camera) with a small resolution sensor. It contains a light source (LED) and two lenses. The LED is structurally mounted at an angle to the working surface. A CMOS sensor receives the reflected beam. According to the comparison of different consecutive pictures by the sensor, it is concluded about the movement of the mouse. Based on these signals, the processor realizes in which direction to move the cursor on the monitor screen.

Gyroscopic Mouse

These mice include a gyroscope that detects movement on the mouse pad and in space.

Induction mouse

These mice use a special pad that operates on the principle of a graphics tablet. The mouse emits electromagnetic waves and the mousepad acts as a receiver. This is how the mouse interacts with the mat.

Computer keyboard

A computer keyboard is a device that allows the user to enter data into a computer. It consists of a set of keys arranged in a specific order. The keyboard is available as a wired or wireless keyboard.

A wired keyboard and a wireless keyboard adapter plug into a USB port.

PS/2 port, which connects the mouse and keyboard, is obsolete. It is rarely found in modern computers.

Typing keys

1 – Control keys. They are used to perform certain actions. They can be used alone or in combination with other keys.

2 – Function keys. These keys execute a specific action on the system. For example, on a notebook, the combination of the «Fn» key and one of the function keys (F1, F2, F3, etc.) increase or decrease the sound, brightness, and so on.

3 – Indicators for enabling Caps Lock, Scroll lock, Num lock.

4 – Keys to work with reading and documents. These include keys: Page Up, Page Down, Home, End, Del, Esc.

5 – Auxiliary keys, enabled by pressing Num lock.

6 – Cursor control keys.

7 – Alphanumeric keys for typing text, numbers, symbols.

Types of keyboards

Membrane keyboards

 membrane keyboard consists of an elastic silicone membrane that squeezes out when the key is pressed.

Pressing the key bridges the contact lines on the printed circuit board.

This is a budget type of keyboard. Eventually, the silicone membrane becomes worn out, and the printed circuit board cannot read the keypress signal.

Mechanical keyboards

Under each mechanical key, you find a separate switch system. Using switches makes the keyboard more reliable. In addition, the keyboard has a characteristic "click" when the key is pressed. This type of keyboard ranks in the more expensive segment than membrane keyboards.

Hybrid keyboards

These keyboards are a combination of mechanical and membrane keyboards. The combination of these types of keyboards provides the membrane keys with tighter feedback and longer life.

Touch keyboards

The touch keyboard is a full-fledged display with a high-precision array that senses every press of the fingers.

Flexible keyboards

Flexible keyboards are available with different numbers of keys. There are also models in different colors, matte and glossy. In addition, this keyboard is sealed and resistant to moisture and dust.

Optical keyboards

The optical keyboard features mechanical moving elements. Once the key is pressed, its rod moves downward and returns back up by spring action. There is an emitter inside the key, which directs an infrared beam to a special sensor.  The rod of the key overlaps the beam, but when pressed, it allows it to connect to the sensor, sending a command to the system.

RGB backlight

RGB backlight allows you to change the color of certain keys and the keyboard as a whole. This can be useful when playing computer games as well as when working.

USB flash drive

A USB-Flash Drive is a non-volatile device for storing and retaining data. Data copied to the device is stored in the flash memory.

A USB flash drive has a limited write and erase cycle (10,000 to 100,000 times). However, the data that is permanently stored on the drive can be read any number of times.

USB flash devices are small, compact, and allow you to connect the device to any computer with a USB connector.

Design

The standard device has an oblong shape and a removable USB cover that protects the USB connector. In addition, it is possible to enable pin-code entry, fingerprint verification, and other data protection methods for USB drives.

Size: about 3-5 centimeters.

Weight: approximately 60g.

Components

1 – USB plug. It allows you to connect the flash drive to a USB reader device.

2 - Microcontroller. This is the chip that transmits data and manages the flash memory.

3 - Flash memory chip. A NAND-type memory chip that is responsible for data storage.

4 - Additional memory chip.

5 - Crystal oscillator. It is used to generate the required frequency for the function of the controller and flash memory. If this device malfunctions, the flash drive is recognized as an "unknown device".

Optical disc

Principles of work

An optical disk includes several layers. A laser beam is used to write data to the disk. The laser creates spiral tracks on the disk, which are composed of pits (depressions). The pits scatter or absorb light, and the surface reflects it.

A laser beam with a certain wavelength is also used to read the information taken from the disk. If the laser hits the pit, the intensity of the light is smaller. The variation in the intensity of the reflected light is converted into an electrical signal.

1 – Compact Disc (CD)

2 – DVD Disc (Digital Versatile Disc)

3 – Blu-ray

The more pits the disc contains, the more information can be recorded on it.

Types

CD

This type of disc was initially created to store audio recordings but later was used to store any data in the binary code. CDs are only used to read the information once written to them.

CD-RW

This type of disc has a writing layer that consists of a special chalcogenide alloy. As the alloy is heated to a certain degree, it transforms from a crystalline state to an amorphous one. This feature is the basis for rewriting, as this transition is reversible. But a CD-RW cannot withstand more than a thousand rewrite cycles.

DVD

DVD has increased the writing capacity while the disc size has remained the same. This was achieved by using a red laser with a wavelength of 650 nanometers and increasing the density of the data recorded (high number of pits).

Blu-ray

Blu-ray offers a higher density of data recording than previous generations. It operates with a shortwave blue-violet laser with a wavelength of 405 nanometers.

Solid-State Drive (SSD)

Description

An SSD (solid-state drive) is a non-volatile storage device.

SSDs are silent, faster, lightweight, and more resistant to damage than hard disk drives. In SSDs, data is stored in microchips (flash memory), instead of rotating metal disks (HDDs). The data processing rate in an SSD processor is much higher than the data writing rate of an HDD. However, SSDs are also much more expensive per gigabyte of memory than a classic hard drive.

SSDs were originally introduced as data storage and transfer devices. These storage devices are divided into two groups: USB drives (1) and memory cards for electronic gadgets (2).

Components

1 - Top cover

2 - The connection type of the SSD to your system.

3 - The DRAM chip - cache memory. It is a temporary data storage with a small volume, which stabilizes the wear and tear of the memory. This cache memory is not available in all SSDs.

4 - NAND-controller - memory controller. This is the processor responsible for SSD performance.

5 - NAND flash memory; it is responsible for data storage.

Hard Disk Drive (HDD)

A hard disk is a data storage device based on the principle of magnetic recording. It records data on hard (aluminum or glass) plates or disks coated with a layer of ferromagnetic material.

Components of a hard drive

1 - Permanent magnet

2 - Head assembly commutator

3 - Rotating frame of read/write heads

4 - Actuator of disk rotation

5 - Disks (one or more)

6 – Read/write heads

7 - Integrated circuit

8 - Chassis

The integrated circuit synchronizes the hard disk drive with your computer, manages all processes, and keeps the rotation speed constant.

The drive spins the disk from 5,400 to 15,000 rpm. The spin rate of the drive depends on the type and quality of the drive's hardware. This affects how fast it runs.

The read/write heads write and read information, and a rotating frame moves them across the area of the rotating disk 60 times per second. The end of the read/write heads is split to handle multiple disks at the same time.

In operation mode, the read/write heads do not touch the surface of the disks due to the airflow. The distance between the read/write head and the disks is only a few nanometers. The lack of physical contact with the surface increases the drive's life.

In non-operational mode, the read/write heads are in a safe area where no contact with the platter surface is possible.

Data Storage

1 - Sectors

2 - Tracks

Data is stored in narrow tracks on the surface of a disk. Over 200,000 of these tracks are generated during disk production. Each track is divided into sectors. A map of tracks and sectors allows the drive to determine where to write to and read from.

The disk's surface is coated with a ferromagnetic film that stores all the information. The read/write head magnetizes a microscopic area (cell) on the disk's surface and adjusts the magnetic moment of such a cell to one of the states zero or one. A bit refers to each of these zero or one states. The bit value corresponds to the value of the magnetic field: plus or minus.

For example, a high-quality picture occupies about 29 million such cells and is distributed over twelve different sectors. This is just a very small area on the surface of the disk.

Thus, according to the law of magnetism, the thin ferromagnetic film of a disk can retain gigabytes of information.