Circuit schematic entry knowledge

1. The significance of electronic circuits

A circuit diagram is a graphic representation of a circuit structure drawn by a convention symbol for the purpose of research and engineering. The actual circuit condition can be known through the circuit diagram. In this way, when we analyze the circuit, we don't have to ponder over the actual object, but just hold a drawing. When designing a circuit, it can also be carried out on a sheet of paper or on a computer. After confirming the improvement, the actual installation can be performed through debugging and improvement until it is successful. We can also use advanced computer software for circuit-aided design, even virtual circuit experiments, and greatly improve work efficiency.

2. The classification of electronic circuit diagram

Commonly encountered electronic circuit diagrams include schematics, block diagrams, assembly drawings, and plate layouts.

1) Schematic

A schematic is a circuit diagram that is used to represent the working principle of an electronic circuit. It is also called an "electrical schematic." This kind of diagram is generally used in designing and analyzing circuits because it directly reflects the structure and working principle of electronic circuits. When the circuit is analyzed, the actual working condition of the circuit can be understood by recognizing the symbols of the various circuit components drawn on the drawings and the connections between them. The following figure shows a schematic of a radio circuit.

2) Block diagram

A block diagram is a circuit diagram that shows the working principle and composition of a circuit using blocks and lines. Basically, this is also a schematic. However, in this kind of drawing, there are almost no other symbols besides the box and the connection. Its main difference from the above schematic diagram is that the circuit diagram shows all the components of the circuit and how they are connected. The block diagram simply divides the circuit installation function into several parts and describes each part as A box in which a simple text description is added and the connections between the boxes are illustrated in the boxes (sometimes with arrows). Therefore, the block diagram can only be used to show the general working principle of the circuit. In addition to the principle of the circuit, the schematic can also be used as a basis for collecting components and making circuits. The following figure shows the block diagram of the above radio circuit.

3) Assembly drawing

It is a kind of drawing used for circuit assembly. The symbols on the drawing are often the physical outline drawing of circuit components. We can complete the assembly of the circuit by simply connecting the circuit components according to the way they are drawn on the diagram. This circuit diagram is generally used by beginners.

The assembly drawings vary according to the assembly template. Most of the applications for electronic products are printed circuit boards described below. Therefore, printed board drawings are the main form of assembly drawings.

In the beginning of electronic knowledge, in order to be able to contact electronic technology earlier, we chose the screw hole plate as the basic mounting template, so the installation diagram will become another mode.

4) Printed board map

The full name of the printed circuit board is "printed circuit board diagram" or "printed circuit board diagram". It is actually the same type of circuit diagram as the assembly diagram, and is used for the actual circuit assembly.

The printed circuit board is first covered with a layer of metal foil on an insulating board, and then the unnecessary metal foil is etched away. The remaining part of the metal foil is used as the connecting line between the circuit components, and then the element in the circuit is The device is mounted on this insulating board and the remaining metal foil on the board is used as the conductive connection between the components to complete the circuit connection. Since the metal on one side or both sides of this circuit board is copper, the printed circuit board is also called "CLCL." The layout of printed circuit board components is often very different from the schematic. This is mainly because, in the design of the printed circuit board, it is mainly considered whether the distribution and connection of all the components are reasonable. It is necessary to consider factors such as component volume, heat dissipation, anti-interference, anti-coupling, etc., and the printed circuit board designed by combining these factors. From the outside, it is difficult to be completely consistent with the schematic; in fact, it can better achieve the function of the circuit.

With the development of science and technology, the production technology of printed circuit boards has now been greatly developed; in addition to single-panel and double-panel, there are many panels, which have been widely used in daily life, industrial production, national defense construction, aerospace industry, and many others. field.

In the four types of circuit diagrams introduced above, the electrical schematic is the most common and most important, able to understand the schematic diagram, it also has a basic grasp of the principle of the circuit, drawing block diagram, design assembly diagrams, plate maps are all compared Easy. It is also very convenient to master the schematics and carry out maintenance and design of electrical appliances. Therefore, the key is to master the schematic.

3. The composition of the circuit diagram

The circuit diagram mainly consists of four parts: symbol, connection, node, and comment.

The symbol of the component represents the component in the actual circuit. Its shape is not necessarily the same as the actual component, or even completely different. But it generally shows the characteristics of the components, and the number of pins is consistent with the actual components.

The connection shows the wire in the actual circuit. Although it is a line in the schematic diagram, it is not a line but a variety of copper foil blocks in the commonly used printed circuit boards, just like many of the radio schematics. The wiring is not necessarily linear in the printed circuit board diagram, but it can also be a certain shape of copper film.

Nodes indicate the connection between several component pins or several wires. All component pins and wires connected to the node are conductive regardless of the number.

The comments are very important in the circuit diagram. All the words in the circuit diagram can be categorized as comments. A closer look at each of the above diagrams will reveal that there are notes in various places in the circuit diagram. They are used to describe the model, name, etc. of the components.

If you do not know the role of the circuit, you can first analyze the relationship between the input and output signals of the circuit. For example, the law of signal change and the relationship between them, the phase problem is the same phase, or anti-phase. The circuit and composition form is an amplifying circuit, an oscillating circuit, a pulse circuit, or a demodulation circuit. The personnel of electrical repair and circuit design are all able to get the job done by analyzing the circuit schematic and understanding the function and working principle of the electrical appliance. As the technical personnel engaged in this work, we must first have excellent basic skills, we must be able to have a general understanding of circuit diagrams with technical parameters, can be divided into functional modules, to identify the signal flow, determine the role of components. To learn how to repair electrical equipment and design circuits, you must master the principles of each unit circuit. The function blocks are divided, and the elements of the entire circuit can be grouped according to different functions, so that each function block forms a combination of elements of a specific function, such as a basic amplification circuit, a switching circuit, a waveform conversion circuit, and the like.