When you get a product, there are many times when there is no circuit. In this case how to tell the rationality of the circuit board and the work of the situation?

This is the physical reduction of the circuit schematic.

In the face of some small objects, or encountered no drawings of electronic products, the need to draw the circuit according to the physical schematic. Have the following:

1. Select the components, such as integrated circuits, transformers, transistors, and so on, which are bulky, pin-and play a major role in the circuit, and then draw from the selected reference pins 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 letter of the Arabic alphabet after the same elements are the same functional unit, so the drawing should be used The The right to distinguish between the same functional unit of the components, is the basis of drawing layout.

3. If the printed circuit board is not marked on the serial number of components, in order to facilitate the analysis and proofreading circuit, it is best to give their own device number. In the design of printed circuit board components, in order to make the copper wire the shortest, generally the same functional unit of the components are relatively concentrated layout. Find a unit from the core role of the device, as long as the follow-up can find the same functional unit of other components.

4. Correctly distinguish between the ground wire, power cord and signal cable of the PCB. To power circuit, for example, power transformer secondary rectifier connected to the negative side of the power supply cathode, and the ground are generally connected between the large-capacity filter capacitor, the capacitor shell has a polarity mark. It is also possible to find the power cord and ground from the three-terminal regulator pins. When the factory wiring in the printed circuit board, in order to prevent self-excitation, anti-interference, the general set of ground copper foil is the widest (high-frequency circuit is often a large area of ​​ground copper), power cord copper, Foil is the narrowest In addition, in both the analog circuit and digital circuits of electronic products, printed circuit boards are often separate the ground, the formation of an independent grounding network, which can also be used as a basis for identification.

5. In order to avoid excessive wiring of the components of the circuit wiring wiring interspersed, resulting in the drawings are chaotic, power and ground can be used in large numbers of terminal marking and grounding symbols. If the components are more, but also the unit circuit separately drawn, and then combined together.

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

7. Master the basic composition of some of the basic circuit components and classical paintings, such as rectifier bridge, voltage regulator circuit and op amp, digital integrated circuits. First of all these circuit directly drawn to form a circuit frame, can improve the efficiency of drawing.

8. Draw circuit diagram, as much as possible to find a similar product circuit diagram for reference, will play a multiplier effect.

The above is the basic skills of an electronic staff.