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How to restore circuit diagram according to circuit board

writer: G January 09, 2018

This is the object is restored to the circuit diagram.

In the face of some small object, or encountered without drawings of electronic products, need to draw circuit schematic according to the kind. Have the following points:

1. Select the volume of large, multi-pin and play a major role in the circuit components such as integrated circuits, transformers, transistors, etc. for the drawing reference, and then select the reference from the pin to draw the picture, to reduce errors.

2. If the printed circuit board marked with the serial number (such as VD870, R330, C466, etc.), because these serial numbers have specific rules, the first Arabic alphabet after the English letters of the same components belong to the same functional unit, drawing should be used by coincidence . The correct distinction between the same functional unit components, drawing layout is the basis.

3. If the board is not marked with the serial number of components, in order to facilitate the analysis and proofreading circuit, it is best to give their own component number. In the design of printed circuit board manufacturing components, in order to minimize the copper foil alignment, the components of the same functional unit is generally relatively concentrated arrangement. Once you find a device that plays a central role in a cell, you can find the other components of the same cell as long as you follow it.

4. The correct distinction between the printed circuit board ground, power lines and signal lines. Taking the power circuit as an example, the negative terminal of the rectifier connected to the power transformer is a positive power supply. Generally, there is a large-capacity filter capacitor connected to the ground. The capacitor has a polarity mark. Also available from the three-terminal regulator pin to find the power cord and ground. 

Factory wiring in the printed circuit board, in order to prevent self-excitation, anti-jamming, the ground wire copper foil is generally set to the widest (high-frequency circuits are often large area grounding copper foil), power line copper foil, copper signal line Foil narrowest. In addition, in both analog circuits and digital circuits in electronic products, printed circuit boards are often separated from their ground to form a separate ground network, which can also be used as a basis for identification.

5. In order to avoid excessive wiring of the component pins, the wiring of the circuit diagram is crossed and interlaced, resulting in a chaotic drawing. The power supply and the ground wire can extensively use the terminal labels and the grounding symbols. If more components, but also separate the unit circuit drawn, and then combined.

6. It is recommended to use transparent tracing paper, with multi-color pen to ground, power lines, signal lines, components, etc. by color classification draw. Modify, and gradually deepen the color, so that visual drawings eye-catching, in order to analyze the circuit.

7. Proficiency in the basic composition of some of the basic circuit components and painting, such as rectifier bridge, voltage regulator and op amp, digital integrated circuits. Draw the unit circuit directly first, form the framework of the circuit diagram, can improve drawing efficiency.

8. Drawing circuit diagram, should try to find a similar product circuit diagram for reference, will play a multiplier effect.

These are the basic skills of an electronic staff member.

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