How to restore circuit diagram by circuit board

When you get a product, there are no circuit diagrams in many cases. In this case, how to tell clearly the principles and work of the circuit board? This is to restore the physical circuit schematics.


In the face of some small objects, or encountered no drawings of electronic products, you need to draw a circuit diagram based on physical objects. There are several points below:

The 1. choice of big volume, multi pin and in circuit plays a major role in components such as integrated circuits, such as transistor transformer, drawing reference piece, and then from the benchmark selection of each pin to start drawing, can reduce error.

2. if the printed board has a component serial number, because these serial numbers have specific rules, the first element of the same number in the English alphabet belongs to the same function unit, so it should be used skillfully when drawing the Arabia. Correctly distinguishing the components of the same function unit is the basis of drawing layout.

3. if the printed circuit board does not mark the serial number of the component, it is better to give the component number for ease of analysis and correction. When designing a printed circuit board, the components of the same function unit are relatively centrally arranged so as to make the copper wire travel the shortest. Find a device unit played a key role, as long as it can find the other components of the same functional unit.

4. correctly distinguish the ground wire, power line and signal line of the printed board. Taking the power supply circuit as an example, the negative end of the secondary rectifier tube of the power transformer is the positive pole of the power supply, and a large capacity filter capacitor is generally connected between the ground wire and the ground wire, and the capacitance casing is provided with a polarity mark. Also available from the three terminal regulator pin to locate the power line and ground wire. Factory in the printed wiring layout, in order to prevent self excitation, interference, the general ground wire copper set the widest (high frequency circuit is often a large area of grounding copper foil), the power line copper foil next, the signal line copper foil narrowest. In addition, in both analog and digital circuits, printed boards often separate their ground lines and form separate ground grids, which can be used as the basis for identification and judgment.

5.in order to avoid the component pin connection is too much, so that the wiring of the circuit diagram crossing, resulting in the mess of plans, power and ground can be used in large quantities, terminal tagging and grounding symbols. If more components, you can also separate the unit circuit, draw, and then mix together.

6. when drawing sketches, it is recommended to use transparent drawing paper, with a multi colored pen, the ground wire, power lines, signal lines, components and other color classification drawn. When modifying, the color is gradually deepened, and the drawing is visually and eye-catching, so as to analyze the circuit.

7. familiar with the basic components and classical drawing methods of the unit circuit, such as rectifier bridge, voltage stabilizing circuit and op amp, digital integrated circuit, etc.. The units are directly drawn and the frame of the circuit diagram is formed, so that the efficiency of the drawing can be improved.

8. schematic drawing, should as far as possible to find the circuit diagram of similar products for reference, it will be twice the result with half the effort.

The above is a basic skill for an electronic worker.


 

(Source: internal information)

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