When I first encountered electronic systems, I could only practice soldering and was eager to understand circuit boards, but I struggled to grasp the essentials.
Later, in the lab and after starting my job, as I accumulated experience in hardware design and debugging, combined with guidance from experienced experts around me, I gradually understood circuit boards and began to recognize various components and their connections. I must say, having a good mentor can significantly accelerate learning; it can take years to understand on your own without guidance.
Now, after more than ten years of work, I can take a brand new circuit board and, after half a day of sorting through it, sketch out the general relationships of the circuit system, thus constructing a schematic. It should be noted that I am not a professional board copier; I purely rely on my experience and understanding of hardware circuits.
As a hardware engineer, I share my experiences to help beginners understand the basic concepts and components of circuit boards from scratch, gradually learning to identify and understand the components, layout, and working principles of circuit boards. This is for the reference of novice friends.
1. Understanding the Basic Structure of Circuit Boards
The circuit board is the core component of electronic devices. For hardware beginners, understanding the various parts of a circuit board and their functions is the first step into the world of electronics. A printed circuit board (PCB) serves as a support platform for electronic components, connecting them to form the desired circuit. Circuit boards are typically made from an insulating material, with patterns of copper or other conductive materials on top.
Types of Circuit Boards
Single-sided board: Only has one layer of conductive material, suitable for simple circuits, such as basic electronic toys.
Double-sided board: Has conductive layers on both sides, connected by vias, commonly found in moderately complex devices.
Multi-layer board: Contains four or more layers, used in complex devices like computer motherboards, with layers isolated by insulating materials.
By observing the layer count marking on the edge of the circuit board (e.g., “4L” indicates 4 layers), one can initially determine the type.
Core Components
Substrate: Usually made of fiberglass (FR4), providing mechanical support and insulation.
Conductive layer: Copper foil etched into traces for signal transmission and power supply.
Solder mask: A green or blue protective layer that prevents short circuits and oxidation.
Silkscreen layer: Labels component numbers (e.g., R1, C2) and polarity markings.
Beginner Task:
Use a magnifying glass to observe the PCB and identify common components (e.g., 0805 resistors, QFP packaged chips).
Refer to IPC-7351 standards to understand the correspondence between component packages and pads.
2. Identifying Key Components and Functions
Passive components – do not require power, mainly resistors, capacitors, and inductors.
Resistor: Limits current or divides voltage, marked on the surface with color bands or numbers (e.g., “472” indicates 4.7kΩ).
Capacitor: Stores charge; electrolytic capacitors have polarity (marked with a “-” or a notch), while ceramic capacitors are non-polarized.
Inductor: Coil-shaped, used for filtering or energy storage, often paired with capacitors to form LC circuits.
Active components – require power.
Diode: Conducts in one direction; the negative terminal is usually marked with a ring or color band.
Transistor: Used to amplify or switch electronic signals. It has three pins (base B, emitter E, collector C) and requires confirmation of polarity through the datasheet.
Integrated Circuit (IC): Multi-pin chip, core functional module (e.g., power management IC, microcontroller).
Other Components
Connectors: Such as USB ports, HDMI connectors, used for external signal input/output.
Test Points (TP): Round pads for measuring key signals with a multimeter or oscilloscope.
3. Mastering Circuit Diagrams and Principle Analysis
The layout of a circuit board is carefully planned by the designer based on the circuit’s functional and performance requirements. The layout includes the placement of components and routing of circuits. Understanding the layout helps beginners grasp the working principles and signal flow of the circuit.
The structure of the circuit board includes the main board, components, wiring, pads, and soldering wires. Each part’s role and how they connect to each other are explained.
Layout design principles include component placement, routing direction, and the layout of ground and power lines. Good layout design significantly impacts circuit performance and stability.
Comparison of Schematics and Layout Diagrams
Schematics show logical connections, while layout diagrams display the actual positions of components.
Beginners can start with simple modules (e.g., power supply section) and gradually expand to more complex functional areas.
Signal Flow Analysis
Centering on the microcontroller, trace its power supply (VCC/GND), clock (crystal oscillator), and I/O pin connections.
Distinguish between analog signals (e.g., sensor inputs) and digital signals (e.g., SPI communication lines) in routing.
Modular Breakdown
Divide the circuit board into power modules, control modules, communication modules, etc., and analyze each one.
For example: The power module typically includes a voltage regulator IC (e.g., LM7805), filtering capacitors, and inductors.
The specific practical process is as follows, which can handle 99% of circuits:
1. Core Chip Identification and Analysis
First, clarify the core functional modules of the board, focusing on the main control processor (e.g., ARM, DSP, or MCU), memory chips (DRAM/Flash), and bridge controllers (e.g., USB to UART chips). It is recommended to first consult the reference design documents provided by the chip manufacturers, as these documents usually contain verified peripheral circuit topologies.
2. In-depth Interpretation of Chip Manuals and Peripheral Design
By repeatedly studying the datasheet, clarify the chip’s electrical characteristics, pin definitions, and typical application circuits. Focus on the following parameters: operating voltage range, driving capability, interface timing requirements, etc. For example, some chips integrate load capacitors for crystal oscillators, reducing the number of external components; while others that do not integrate them require external 30pF capacitors to match the crystal frequency. Peripheral circuit design should align with the recommended topologies in the manual, such as power filtering and signal matching resistors.
3. Layered Planning of Clock Systems
The clock circuit needs to distinguish between the main clock and sub-module clocks:
Main clock: Typically uses a high-frequency active crystal oscillator (e.g., 24MHz) or a passive crystal (e.g., 8MHz), and the startup circuit must be configured according to the manual’s requirements.
Some chips emphasize enabling the oscillator circuit through registers and setting the PLL reference source (otherwise, there will be no clock signal);
RTC clock: Uses a 32.768kHz crystal oscillator, paying attention to capacitor matching and anti-interference layout.
Clock Monitoring: Some chips have built-in vibration detection, which can automatically switch to a backup clock source to enhance reliability, which is crucial for high-reliability systems.
4. Power Architecture Design and Selection
Power type determination: Switching power supplies (including inductors, high efficiency) are used for high-current modules (e.g., processor core power supply); linear power supplies (no inductors, low noise) are suitable for low-power analog circuits. For example, a certain DSP system uses the TPS767D318 chip to output 1.8V/3.3V while separating analog/digital grounds to suppress interference.
System-level considerations: Analyze input/output power requirements, ripple tolerance, power-up timing, etc. It is recommended to plan the power tree in detail to ensure the power supply timing of each module matches.
5. Standardized Implementation of Interface Circuits
Physical layer design: Design ESD protection and impedance matching circuits according to interface specifications (e.g., USB2.0, HDMI). For example, the CP2102 chip can achieve USB to UART bridging, but the differential signal lines must be configured according to the manual.
Signal Integrity: High-speed interfaces (e.g., Ethernet) need to consider trace length matching and termination resistors, following layout rules to avoid right-angle traces.
6. Modular Integration and Verification
Connect the above modules through buses (e.g., data/address buses) and add necessary pull-up/pull-down resistors. It is recommended to trace the bus connections starting from the CPU and verify functionality module by module. Finally, integrate component parameters through the BOM table to ensure package compatibility.
Typical Classic Circuit Accumulation
Remember common topologies:
▸ Switching power supply: Inductor + MOSFET + control IC
▸ Operational amplifier circuit: Feedback network configuration
▸ Microcontroller minimum system: Crystal oscillator + reset circuit
Instance Practice:
Module division mnemonic:
“Power supply, signal transmission, control logic, interface communication”
Find a simple development board (e.g., Arduino) and label the power module (LDO/DC-DC), MCU core area, sensor interface, communication interface (USB/UART).
4. Using Tools to Assist Analysis
During the learning process, using some tools can also be helpful. For example, a digital multimeter can be used to test the continuity and resistance values on the circuit board, an oscilloscope can be used to observe signal waveforms, and a magnifying glass can help you see small components and connections on the circuit board more clearly.
Basic Tools
Magnifying glass or microscope: For silkscreen identification/solder joint inspection, observing small component markings and soldering quality.
Multimeter: Continuity testing: Continuity testing/voltage measurement to confirm whether wire connections are normal.
Voltage measurement: Check the output of the power module (e.g., whether 5V is stable).
Oscilloscope: Capture signal waveforms (e.g., whether PWM output is distorted).
Advanced Tools
Thermal imaging camera: Locate heating components, identify short-circuited or overloaded components (abnormal hot spots).
Logic analyzer: Analyze digital signal protocols (e.g., I2C, UART).
Spectrum analyzer, etc.
Instance Practice:
Use an oscilloscope to capture actual waveforms (e.g., I2C SCL/SDA signals).
5. Practical Methods and Experience Accumulation
Theoretical knowledge needs to be consolidated through practice. Engage in actual circuit design and production experiments to deepen understanding and mastery of circuit boards through hands-on practice.
Beginners can practice in the following ways:
Disassemble old circuit boards:
Choose circuit boards from old appliances (e.g., radios) and compare the schematics with the actual layout.
Record component layout patterns (e.g., high-frequency circuits away from power modules).
Use circuit simulation software:
Currently, simulation tools are becoming increasingly essential, and simulating the working principles of circuits is a very important and effective step.
Modular soldering practice:
Build basic circuits (e.g., LED blinking circuit) on a breadboard, then transition to PCB soldering.
Pay attention to soldering temperature (recommended below 350°C) to avoid damaging components.
Troubleshooting Cases
Case 1: A certain system device does not power on.
Steps: Check the fuse → Measure input voltage → Test the output of the voltage regulator IC.
Case 2: “MCU cannot start” – Check the three elements of power supply, clock, and reset.
Case 3: “Communication abnormal” – Check level matching, termination resistors, and signal integrity.
Solutions:
Refer to the schematic and use the elimination method to test in segments (e.g., disconnect peripheral modules and test core functions individually).
Phased Practice
Level 1: Analyze the power board (e.g., mobile phone charger)
Level 2: Understand the microcontroller development board (e.g., STM32F4 Discovery)
Level 3: Disassemble complex systems (e.g., router motherboard)
6. Learning Resources and Advanced Suggestions
Electronics technology is a constantly evolving field, and continuous learning of new knowledge and skills is very important for hardware beginners. You can continuously improve by reading books, participating in online courses, and joining electronics enthusiast communities.
Books and Online Courses
Must-read standards:
IPC-2221 (General PCB Design Standards)
JESD22 (Reliability Testing Methods)
Book Extensions:
Deepen theory with “High-Speed Digital Design” and “Signal Integrity Analysis.”
“Fundamentals of Electronic Circuits” (Tsinghua University Press): Covers classic circuit analysis and design.
Coursera “Hardware Description Language and PCB Design”: Learn tools like Altium Designer.
Key Mnemonic Summary
“First modules, then details” – First determine functional partitions, then analyze specific circuits.
“Power is blood, ground is bone” – Prioritize clarifying power supply and grounding networks.
“Signal routing looks at paths” – Focus on the return paths and reference planes of high-speed signals.
“Tools never leave hand” – Frequently use practical measurements to validate hypotheses, avoiding theoretical discussions.
Conclusion
For hardware beginners, understanding circuit boards is a challenge, but through gradual learning and practice, this skill can be mastered. From basic component recognition to complex circuit analysis, beginners can gradually build a systematic understanding of circuit boards, from “recognizing components” to “analyzing functions,” ultimately achieving independent design and debugging. Each step is a process of growth.
The most important thing is to maintain patience, curiosity, and continuous learning; hardware beginners can certainly become experts in the field of electronics.
According to my method, through the above systematic training, beginners can establish circuit board analysis capabilities within 3-6 months.