The following are 8 ways to restore the PCB schematic diagram in accordance with the PCB board:
- Select large-volume, multi-pin, and electronic components such as integrated circuits, transformers, transistors, etc. that play a major role in the circuit, and then extract from the selected reference pins to reduce errors.
- If the component numbers (such as VD870, R330, C466, etc.) are marked on the PCB, since these serial numbers have specific rules, the components with the same Arabic numerals after the English letters are the same functional units, so the drawing should be used. Correctly distinguishing the components of the same functional unit is the basis for drawing the pcb layout.
- If the serial numbers of the components are not marked on the printed board, it is best to number the components yourself for easy analysis and proofreading. When the manufacturer designs the printed circuit board components, generally the components of the same functional unit will be arranged relatively to minimize the copper foil traces. Once the device with the core function is found, as long as it can be found, other components of the same functional unit can be found.
- Correctly distinguish the ground wire, power line and signal line of the printed board. Take the power supply circuit as an example, the negative pole of the rectifier connected to the secondary of the power transformer is the positive pole of the power supply, and generally a large-capacity filter capacitor is connected between the ground and the ground, and the shell of the capacitor has a polarity mark. The power line and the ground wire can also be found from the pins of the three-terminal voltage regulator. When the factory routes the printed circuit board, in order to prevent self-excitation and anti-interference, the ground copper foil is generally set to the widest (high-frequency circuits often have a large area of grounded copper foil), the power copper foil is the second, and the signal copper foil is the narrowest. In addition, in electronic products with both analog circuits and digital circuits, the printed board often separates its ground wires to form an independent grounding grid, which can also be used as a basis for identification and judgment.
- In order to avoid excessive wiring of components and the crossover and interleaving of the wiring of the circuit diagram, resulting in messy pictures, terminal marks and grounding symbols can be used extensively for the power line and the ground wire. If there are many components, the unit circuits can be drawn separately and then combined.
- When drawing a sketch, it is recommended to use transparent tracing paper and draw the ground wire, power line, signal line, components, etc. with colored pens according to the color. When modifying, gradually deepen the color to make the drawing visually striking and easy to analyze the circuit.
- Proficiency in mastering the basic composition and classic drawing methods of some unit circuits, such as rectifier bridges, voltage regulator circuits, op amps, digital integrated circuits, etc. These unit circuits are directly drawn to form the framework of the circuit diagram, which can improve the drawing efficiency.
- When drawing a circuit diagram, try to find the circuit diagram of similar products as a reference, which can get twice the result with half the effort.