Devices
Devices
Lesson Objectives
- Sensors
- Actuators
- Monitoring and control applications
- Embedded computers
Introduction
- Monitoring and control systems are used widely in several areas such as home appliances, security systems, traffic lights, and industries.
- The basic approach is to measure a physical quantity such as temperature, pressure, light intensity, or volume of a gas.
- The measured value is sent to a computer. This is done by a sensor. A sensor is a hardware device that measures a physical quantity and transmits the value to a computer that controls the system.
| Types of Systems | |
Monitoring | The value received is checked with the allowable values.If the values do not satisfy the safety requirements, a warning is sent so that humans can take necessary action. The warning may be a text message or the ringing of an alarm. |
Monitoring & Controlling | In addition to monitoring, some systems are designed to control the system. If a value is not within the allowable limits, the computer sends instructions to that part of the system that could reverse the cause of change. The part of the system that is responsible for control operation is the actuator. |
Control System
- The actuator is a hardware device that receives the signals from the computer and adjusts the setting of a controlling device.
- In monitoring and control systems, there is feedback to continually process the measurements and take necessary action.
Analog-to-Digital Converters
- Physical quantities are analog in nature; that is, the values are constantly changing, and to measure these values, we need to interpret the readings.
- For example, to read the time using an analog clock, we need to look at the hands of the clock to state the hours and minutes.
- Computers cannot read analog values directly. Analog values are converted to discrete digital values so that the computer can process them.
Digital-to-Analog Converters
- The control signals from the computer are digital in nature and are converted to analog signals.
- For example, a motor requires an electric signal instead of a digital signal from a computer.
Sensors
- Sensors are devices that can read physical quantities such as temperature, light, motion, and so on.
- Physical quantities are analog in nature.
- For the computer to interpret these values, an analog-to-digital converter (ADC) is used.
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Monitoring & Control Applications
- The DAC converts the digital data from the computer into analog values that can control the output devices.
- A computer can control devices such as motors, valves, etc. by using a digital-to-analog converter (DAC).
- An actuator is an electromechanical device that controls electrical devices.
- Its operation is similar to that of a switch. It switches the electrical device ON and OFF according to the signals from the computer.
Embedded Computers
- Embedded computers are designed to perform a dedicated function within a large mechanical or electrical system.
- For example: MP3 players, digital cameras, and GPS trackers.
- A computer-embedded point-of-sale billing system is also an example.
- An embedded system is programmed during its manufacturing stage.
- Users operate these devices using interfaces such as buttons or touchscreens provided.
- Embedded systems are more reliable when compared to general-purpose computers.
- This is due to the specialized hardware and dedicated software designed specifically for a particular function.
Wearable Gadgets
- Wearable gadgets are a category of devices that can be worn by the consumer to track information related to health and fitness.
- Some wearable gadgets have small motion sensors that take photos and transfer them to smartphones.
Raspberry Pi
- Raspberry Pi is a low-cost single-board computer.
- It is available in RAM of 256 MB, 512 MB and 1 GB. It has a 1.4 GHz CPU. A full Linux OS can be installed.
- This can be operated as a desktop machine once the input and output devices are connected.
- Developers are using this for home and industrial automation. Also used in digital cameras and digital media players.
Arduino
- Arduino designs and manufactures single-board microcontrollers.
- The hardware and software are open-sourced.
- This board is equipped with input and output ports that can be connected to other circuits for incorporating real input values.
- Programs can be transferred from a computer, such as a PC, to the Arduino through a USB connection.
- For example: Sensing the temperature of a boiler and switching on an LED when the temperature rises above a certain value.
Embedded Systems
- As embedded systems are dedicated for a particular cost, their size is reduced and performance is improved.
- The software in these systems is also dedicated to a single function.
- The user will not be able to modify the program.
- Users can only interact with the embedded system using the buttons provided or a touch screen.
- Embedded systems are robust and reliable when compared to general-purpose systems. This is due to its dedicated functionality.
- Embedded systems are low-power devices. It is also low cost and hence, is advantageous in large-scale productions. For example: controller of washing machine panel, television, etc.
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