Friday, May 20, 2011

【 Weak current College 】 how kind draw electrical schematics 】

Maintenance personnel often encounter no drawings of electronic products, according to the real draw circuit schematics. This is the beginner must master the basic skills, the following describes the methods and techniques.

1. Select the volume, PIN number and play a major role in the circuit of components such as IC, transformer, transistor and other painting map Datum element, and then select the baseline start for the PIN, you can reduce the error paint.

2. If the printed circuit board is marked with a symbol number (such as VD870, R330, C466, etc.), as these numbers have specific rules, after the first letters of the Arabic numerals of the same components within the same functional unit, so the paint should be specially with use. Distinguish the same functional unit of components, is the basis for drawing the layout.

3. If the PCB on the ordinal number of the components, for ease of analysis and correction circuit, the best one gives the number of components. Manufacturing plant in the design of PCB arrange components so that the shortest foil alignment, generally the same functional units of the relative concentration of components. Find a unit play a central role in the device, as long as this allows you to find the same functional units of other components.

4. distinguish PCB's ground, power and signal cables. To the power circuit, for example, power transformer secondary received negative side of the rectifier tubes for power cathode, and Earth are attached between General bulk filter capacitor, the capacitor shell have polarity signs. May also be obtained from the three-Terminal regulators pins to find out the power and ground wire. Factory in PCB wiring, in order to prevent the self-excited, anti-interference, general ground wire copper foil set most wide (high-frequency circuits are often large grounding copper foil), power cables copper foil, copper foil most narrow signal lines. In addition, in both analog and digital circuits of electronic products, PCB often separated from their respective ground to form independent grounding network, this can also be used as the basis for recognition of judgments.

5. in order to avoid too many components pin wiring makes the circuit wiring cross interspersed, resulting in the art of illustration messy, power and ground can make heavy use of terminal symbols the callout and grounding. If the components are more, you can also separate the unit circuit, painted and then grouped together.

6. sketch, recommend using transparent tracing paper, multiple color pen will ground wire, power cable, signal cable, components such as draw by color classification. Modify, gradually deepening colors, making the drawing intuitive smart so that analysis of the circuit.

7. be familiar with some basic cell circuit and composed form, such as the classic drawing rectifier bridge, voltage circuit and amplifier, digital integrated circuit, etc. First direct the cell circuit, circuit diagrams drawn framework that would improve the efficiency of the paint.

8. draw a circuit diagram, should as much as possible to find a similar product of circuit diagrams for reference, will play a more effective role.

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