2.1. Embedded system hardware design
2.1.1. Introduction to embedded system hardware design
Embedded system hardware is the physical part of an embedded system that provides the components needed to receive inputs, process data, and produce outputs for a specific application.
Many embedded systems project composed by different hardware parts like power supply part, input part, processing part and output part and each is made by different component according its purpose.
2.1.2. Embedded system hardware parts
2.1.2.1. Power supply part
Power supply is part which responsible to distribute current needed each part of embedded system. Many electronic devices use direct current which has stored in battery or converted from alternating current.
To convert AC current to DC current, there some important components that play crucial role in that conversion.
Some power supply components:
a) Transformer
A transformer is a passive electrical device that transfers electrical energy between two or more circuits through electromagnetic induction, usually to step up or step down voltage levels without changing the frequency.
If it step up transformer, it receive low voltage on primary winding and produce higher voltage on secondary winding. For example it can be connected on 12 V and get 220 V on its output.
b) Rectifier
A rectifier is an electronic circuit that converts AC (Alternating Current) into DC (Direct Current). Rectifiers are very important in power supplies because most electronic circuits require DC voltage to operate.
Main types of rectifiers
- Half-Wave Rectifier:
- Full-Wave Rectifier:
- Uses a centre-tapped transformer.
- Usually uses 2 diodes.
- Uses 4 diodes.
- Does not require a centre-tapped transformer.
It uses one diode. The diode allows only one half-cycle of the AC waveform to pass.
It converts both halves of the AC waveform into DC.
There are two common forms of Full-Wave Rectifier
1. Centre-tapped full-wave rectifier:
2. Bridge rectifier:
C) Capacitor
capacitor is a passive electronic component that stores electrical energy in an electric field
Main types of capacitors
- A. Ceramic capacitors:
- B. Electrolytic capacitors:
- C. Tantalum capacitors:
- D. Variable capacitors:
They are generally non-polarized, meaning they can be connected in either direction.
Most electrolytic capacitors are polarized. They have a positive (+) and negative (−) terminal and must be connected correctly.
Connecting one incorrectly can cause overheating, leakage, or even failure.
Electrolytic capacitors can provide relatively large capacitance values.
Tantalum capacitors are a type of polarized electrolytic capacitor that use tantalum metal to achieve high capacitance in a very small size. They offer great stability, low leakage current, and a long life, but they cost more than aluminum alternatives and can fail violently if connected backward.
Tantalum capacitors are also generally polarized and are used where relatively high capacitance is required in a small package.
Their capacitance can be adjusted mechanically or electronically.
d) Voltage regulator
A voltage regulator is an electronic circuit or device that maintains a stable output voltage even when the input voltage or load changes
It is very important in power supplies because electronic components such as microcontrollers, sensors, ICs, and communication circuits often require a specific, stable voltage.
Suppose you have a power supply that produces approximately 12 V DC, but your microcontroller requires 5 V DC.
Connecting 12 V directly to a 5 V device could damage it.
A regulator can convert 12 V DC → 5 V DC and maintain the output close to 5 V.
Main functions of a regulator
- Maintain a constant output voltage
- Reduce voltage fluctuations
- Protect electronic circuits from excessive voltage
- Provide a stable supply to ICs and microcontrollers
- Reduce the effects of changes in load current
- Improve the quality of a DC power supply
2.1.2.2. Input part
The input part of an embedded system is the section responsible for collecting information from the outside world and sending that information to the processing unit.
For example, in an automatic temperature-control system, a temperature sensor detects the surrounding temperature and sends a signal to the microcontroller. The microcontroller then decides what action to take.
In that case, temperature sensor like DHT11 will serves as an input part to our embedded system
Importance of input part to embedded system
- Detects physical conditions
- Measures physical quantities
- Receives commands from users
- Converts physical information into electrical signals
- Sends the signals to the processor
Input devices in embedded systems
There are many different input devices.
A. SENSORS
Sensors are among the most important input devices.
They detect physical quantities and convert them in electrical signal
some examples of physical quantities are:
- Temperature
- Light
- Pressure
- Humidity
- Motion
- Etc…
Example:
Temperature → Temperature sensor → Electrical signal → Microcontroller
B. Switches and push buttons
A switch is another simple input device.
For example, a push button can tell a microcontroller whether a user has pressed a button.
The input may be:
- LOW = Button not pressed
- HIGH = Button pressed
Example:
In an automatic door system:
Push button → Microcontroller → Motor
When the user presses the button, the microcontroller receives the input and activates the motor.
C. Keypads
A keypad allows a user to enter information into an embedded system.
For example, a push button can tell a microcontroller whether a user has pressed a button.
Examples include:
- Telephone keypads
- Security systems
- ATMs
- Digital locks
- Industrial control panels
Example:
Keypad → Microcontroller → Display
When the user enters a password, the microcontroller reads the keypad input and determines whether the password is correct
D. Communication inputs
Not all inputs come from sensors.
An embedded system can also receive data from another electronic device through communication interfaces
Examples include:
- UART
- SPI
- I²C
- CAN
- USB
- Ethernet
- Bluetooth
- Wi-Fi
Example:
Bluetooth module → UART → Microcontroller
Or
Temperature sensor → I²C → Microcontroller
2.1.2.3. Signal Processor Part in an Embedded System
The signal processor part of an embedded system is the section responsible for receiving input signals, processing or analyzing them, and producing useful information or control signals for the rest of the system.
Signal processor = the part that transforms raw input signals into meaningful information or control decisions.
In many embedded systems, the signal processor is implemented using a microcontroller (MCU), microprocessor (MPU), Digital Signal Processor (DSP), or specialized processor.
A signal is information represented in an electrical form.
Signals can represent by :
- Temperature
- Sound
- Light
- Pressure
- Speed
- Position
The processor receives these signals and performs operations on them.
For example
A temperature sensor may produce:
1.0 V → 25°C
The processor can read this voltage, calculate the corresponding temperature, and decide whether a cooling fan should be turned ON or OFF.
Main functions of the signal processor
The signal-processing section can perform several operations.
- A. Signal acquisition: The processor receives data from sensors or other input devices.
- B. Signal conversion: An ADC (Analog-to-Digital Converter) converts an analog signal into digital data. Some systems also use a DAC (Digital-to-Analog Converter)
- C. Signal filtering: Signals can contain unwanted noise. The processor can apply digital filters to remove or reduce this noise.
- D. Mathematical calculations: The processor can perform calculations on the input signal.
- E. Decision making: After processing the signal, the processor can make a decision.
Types of processors
A. Microcontroller (MCU)
A microcontroller contains several components in one chip, such as:
- CPU
- RAM
- Flash memory
- Timers
- ADC
- Communication interfaces
- GPIO
Examples of microcontrollers
- Arduino-compatible microcontrollers
- STM32
- PIC
- AVR
- ESP32
B. Digital Signal Processor (DSP)
A DSP is specifically designed to efficiently process digital signals.
DSPs are particularly useful for:
- Audio processing
- Image processing
- Video processing
C. Microprocessor (MPU)
A microprocessor generally provides more processing power but often requires external components such as RAM and storage.
2.1.2.4. Output Part of an Embedded System
The output part of an embedded system is the section responsible for delivering the result of the system’s processing to the outside world.
Output = the action or information produced by an embedded system after processing the input.
The output section receives a command or processed information from the processor and converts it into a useful physical action or human-readable information.
It can:
- Turn a device ON or OFF
- Control the speed of a motor
- Produce sound
- Display information
- Generate light
- Open or close a valve
- Activate an alarm
- Send information to another system
Common output devices
There are many types of output devices used in embedded systems.
A. LEDs
An LED (Light Emitting Diode) is one of the simplest output devices.
A microcontroller can control an LED by sending a digital signal and the LED gives light.
Example:
Push button → Microcontroller → LED
When the button is pressed, the microcontroller can turn the LED ON.
B. Displays
Displays provide information directly to the user.
Example:
Temperature Sensor → Microcontroller → LCD
The LCD could display: Temperature = 28°C
C. Motors
Motors are very important output devices in embedded systems.
A processor can control a motor to produce mechanical movement.
Example:
- DC motors
- Stepper motors
- Servo motors
- Brushless DC motors
Temperature Sensor → Microcontroller → Motor Driver → Fan Motor
The LCD could display: Temperature = 28°C
D. Relays
A relay is an electrically controlled switch.
A microcontroller can control a relay, which can then switch another electrical device.
Example:
- DC motors
- Stepper motors
- Servo motors
- Brushless DC motors
Microcontroller → Relay → Water Pump
The microcontroller itself may not be able to supply enough current to operate the pump directly.
The relay provides an interface between the low-power control circuit and the higher-power load.
E. Buzzers and speakers
A buzzer can produce an audible warning.
Smoke Sensor → Microcontroller → Buzzer
If smoke is detected:
Smoke detected → Processor → Buzzer ON
This can be used in:
- Fire alarms
- Security systems
- Industrial warning systems
- Medical equipment
Speakers can also be used for more complex audio output.
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