Understanding the Circuit Board Components to Grasp the Fundamentals of Electronics
Recognizing Circuit Board Components
Circuit Board Components are a collective term encompassing both elements and devices. They form the building blocks of electronic parts and small machines or instruments, often consisting of several smaller parts, allowing for interchangeability across similar products. These essential components typically refer to parts used in industries such as electrical appliances, radio, and instrumentation. Examples include ceramic capacitors, transistors, balance springs, and mainsprings, among other sub-components.
On a PCB (Printed Circuit Board), letters are used as abbreviations to denote different electronic components. These letters are typically followed by numbers, which identify the specific electrical component type in the PCB schematic. Here's what each abbreviation stands for:
● T: Transformer
● C: Capacitor, a essential component that stores electrical charge and energy
● R: Resistor
● L: Inductor, a electrical component that stores energy in a magnetic field
● Q: Transistor
● U: Integrated Circuit (Chip)
● D: Diode
● UR: Silicon Controlled Rectifier (SCR), used in power source control industrial applications with digital circuit
● VC: Voltage Controller, a rectifier that converts AC power to DC
● UF: Frequency Converter, controls the power supply frequency to an AC motor
● UC: Converter, changes voltage level, frequency, phase, or other electrical characteristics
● UI: Inverter, converts DC power source to AC with fixed or variable frequency and voltage
● M: Motor
● MA: Asynchronous Motor (Induction Motor), an AC motor converting electrical to mechanical energy
● MS: Synchronous Motor, used for converting electrical to mechanical energy with synchronized speed
● MD: DC Motor, converts DC electrical energy to mechanical energy
● MW: Wound Rotor Induction Motor
● MC: Squirrel Cage Motor, a common type of three-phase induction motor
● YM: Electric Valve, uses an actuator for valve control
● YV: Solenoid Valve, medical equipment controlled by electromagnetic means
These identifiers help in navigating and understanding electronic circuit diagrams by linking the physical component type on the board to their representations in schematic diagrams.
Electronic components are composed of two major parts: electronic devices and electronic elements
● Electronic Devices: These are finished products manufactured without altering the molecular composition. Examples include resistors, capacitors, and inductors. Since these devices do not generate electrons or exert control over voltage and electric current, they are referred to as passive components.
● Electronic Elements: These are finished products whose molecular structure has been altered during manufacturing. Examples include transistors, vacuum tubes, and integrated circuits. Since they have the capability to generate electrons and control or modify voltage and electric current (through amplification, switching, rectification, detection, oscillation, modulation, etc.), they are known as active components.
Electronic devices can be broadly divided into 12 categories, which fall under two main groups: vacuum electronic devices and semiconductor devices.
An Introduction to Commonly Used IC Board Components
Common electronic components include: resistors, film capacitors, inductors, linear potentiometers, transformers, DIODES, transistors, MOSFETs, integrated circuits, and so on. Now let's introduce several common components.
Resistors (R):
The types of resistors are crucial components in modern electronics, primarily used to impede the flow of electric current. The two key parameters that define a resistor are its resistance value and power rating. The resistance value indicates how much the resistor opposes the flow of current, measured in ohms (Ω). Beyond the basic unit, resistances can also be expressed in kilohms (kΩ) and megohms (MΩ).
The power rating, measured in watts (W), specifies the maximum amount of power a resistor can handle before it risks being damaged. Common ratings include 1/16W, 1/8W, 1/4W, 1/2W, 1W, and 2W. Exceeding these limits can lead to the resistor overheating and failing.
Resistors come in various types based on their construction materials:
● Cement Resistors: Known for low cost and high power consumption but tend to have high thermal noise and less precise resistance values.
● Carbon Film Resistors: Offer a balance between cost and performance.
● Metal Film Resistors: Provide high precision, stability, and low noise in a compact size.
● Metal Oxide Film Resistors: Known for high stability under varying environmental conditions.
Furthermore, resistors can be classified based on whether their resistance is fixed or variable. Variable resistors include trimmer resistors and potentiometers, which allow for adjusting resistance as needed.
Capacitors (C):
Capacitance is a measure of a capacitor's ability to store electric charge. It is defined by the amount of charge needed to increase the potential difference between the plates of the capacitor by one volt. Essentially, a capacitor acts as a static charge storage medium, similar to a bucket that holds water. In ideal conditions, excluding leakage and self-discharge effects (which are more pronounced in electrolytic capacitors), the stored charge can remain indefinitely.
Types of capacitors are indispensable in the electric fields of electronics and power management with extensive applications including power filtering, electrical signal coupling, electronic signal filtering, resonance electronic circuits, and DC blocking. The symbol for capacitance is C.
The relationship governing capacitance is given by: C=εS/4πkd=Q/U
where (\epsilon) is the permittivity of the dielectric material between the plates, (S) is the PCB surface area of the plates, (d) is the distance between the plates, (Q) is the charge, and (U) is the voltage across the plates.
In the International System of Units (SI), the unit of capacitance is the farad (F). However, due to the large size of a farad, practical capacitors are typically measured in smaller units:
● Millifarads (mF)
● Microfarads (μF)
● Nanofarads (nF)
● Picofarads (pF), also known as micro-microfarads
The conversion relationships are as follows:
1 Farad (F) = 1000 millifarads (mF) = 1,000,000 microfarads (μF)
1 Microfarad (μF) = 1000 nanofarads (nF) = 1,000,000 picofarads (pF)
Inductors:
An inductor is an electronic component that stores energy in the form of a magnetic field when electrical current passes through it. Structurally similar to a transformer but with only one winding, inductors resist changes in current. When a circuit is initially closed and there is no current flowing, an inductor will oppose the establishment of current flow. Conversely, when current is already flowing and the circuit is opened, the inductor attempts to maintain the current flow. Inductors are also known as chokes, reactors, or dynamic reactors, due to their role in controlling current flow within circuits.
Potentiometers:
Potentiometers are adjustable resistors with three terminals, allowing for the regulation of resistance according to a specific pattern. Typically composed of a resistive element and a movable wiper, when the wiper moves along the resistive element, it produces a resistance or voltage output proportional to the displacement. Potentiometers can function as both three-terminal or two-terminal devices, the latter being a variable resistor.
Comprising a resistive body and a rotating or sliding mechanism, potentiometers adjust the contact point along the resistive body against fixed contacts. This adjustment results in a variable voltage between the moving and fixed contacts, often used in voltage regulation applications. Potentiometers essentially operate as sliding rheostats and come in various design process, commonly employed in audio equipment for volume control and in laser devices for adjusting power levels.
Diodes:
A diode is an electronic component with positive terminals and negative terminal that primarily allows electricity flow in one direction. This directional behavior is commonly used for its rectifying functions, converting alternating current (AC) to direct current (DC). Another type of light-emitting diode, the varicap diode, acts as an electronically adjustable capacitor.
The main characteristic of diodes is their ability to permit current flow in the forward direction (forward-biased) while blocking it in the reverse direction (reverse-biased). Thus, a diode can be compared to an electronic check valve. However, in practice, diodes do not exhibit ideal on/off characteristics. Instead, they have complex nonlinear properties, determined by their specific design and type. Beyond serving as switches, diodes perform various other functions in electronic circuits.
Transistors (Bipolar Junction Transistors - BJTs):
The types of transistor, fully known as a semiconductor transistor or bipolar junction transistor (BJT), is a current-controlled semiconductor device. It amplifies weak signals into larger electrical signals and also functions as a contactless switch. As a fundamental building block of modern electronics, transistors are pivotal for current amplification.
The types of transistor are constructed on a semiconductor substrate with two closely spaced PN junctions, dividing the device into three regions: the base region (middle) and the emitter and collector regions (sides). The two configurations are PNP and NPN, each representing different doping arrangements.
MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors):
MOSFETs are a type of field-effect transistor characterized by a metal-oxide-semiconductor structure. Also referred to as metal-insulator-semiconductor (MIS) transistors, MOSFETs have interchangeable source and drain terminals formed within N-type regions in a P-type substrate. These symmetrical devices maintain performance even when terminals are reversed.
MOSFETs are renowned for their excellent switching capabilities, making them ideal for use in electrical circuits requiring electronic switches. They are widely employed in applications such as switch-mode power supplies, motor drivers, and dimming controls due to their efficient operation and versatile functionality.
Transformers:
PCB transformers refer to transformers placed on printed circuit boards, or those containing polychlorinated biphenyls. Typically surface-mounted devices, they are designed to provide necessary voltage regulation or current conversion directly on the circuit board. These transformers come in a variety of specifications and sizes, allowing for selection across a wide range of applications. There are also cost-effective hole components available that make electronic element production more economically viable. Among these innovations, coreless PCB transformers stand out, significantly reducing the size of the transformer. Although still largely experimental, their potential application range is vast.
Silicon Controlled Rectifiers (SCRs):
A silicon controlled rectifier is a widely used power semiconductor device capable of controlling the switching of electrical power ranging from kilowatts to megawatts. Structurally, it resembles a reverse-blocking triode-type thyristor composed of four conductive layers with three PN junctions (PN-PN configuration). It features three external terminals: cathode, anode, and gate.
The SCR's reverse characteristics are similar to those of PN junction diodes under reverse bias (anode connected negatively). In forward conditions, the device exhibits high impedance in its off state (forward blocking state), represented by the solid line below the dashed line in the first quadrant of the I-V characteristic graph. When the forward instantaneous voltage exceeds the breakover voltage, the SCR rapidly transitions to a low voltage, high current conducting state.
These descriptions provide an overview of common PCB components. For those interested in sourcing such hole components, platforms like UNIKEYIC offer access to a wide range of high-quality products tailored to various needs.
