Commonly used devices on circuit boards include resistors, capacitors, diodes, triodes, thyristors, touch switches, liquid crystals, light emitting diodes, buzzers, various sensors, chips, relays, and so on.

        Moreover, electronic components have different packaging types, and different types of components have the same appearance, but their internal structures and uses are greatly different. For example, TO220 packaged components may be triodes, thyristors, field effect transistors, or dual diodes. Components packaged in TO-3 include transistors, integrated circuits, and so on. Diodes also have several types of packaging, glass packaging, plastic packaging, and bolt packaging. How do you identify them? Let's take a look together.

1. Shape recognition method

        Appearance recognition of electronic components refers to the correspondence between the physical object and the name. Its purpose is to obtain an electronic component that can know what it is and its circuit graphical symbol. As shown in the figure, there are three types of physical electronic components

2. Circuit graphical symbol recognition

        Understanding the identification information in circuit graphical symbols is helpful for the memory of circuit symbols and for the analysis of circuit working principles. The following points are mainly explained about identifying graphical symbols for electronic components and circuits.

        (1) The circuit graphical symbols of electronic components contain a lot of graphic information for circuit analysis. The most basic thing is to understand how many pins the component has through the circuit graphical symbols. If the pins have positive and negative polarity, there will also be various expressions in the circuit graphical symbols.

        (2) Component circuit graphical symbols have the characteristics of visualization, and each stroke or symbol of the circuit graphical symbol expresses specific drawing recognition information.

        (3) The letters in the circuit graphic symbols are the letters of the English word for the component, such as T for transformers, which are the letters of the English Transformer. Understanding professional English can also help identify circuit graphical symbols in circuit diagrams, which is very beneficial for some circuit diagrams.

3. Pin identification and pin polarity identification

        Many electronic components have polarity in their pins and cannot be substituted for each other. Therefore, pin identification and pin polarity identification must be performed through circuit graphical symbols or physical components.

        There are two methods for pin identification and pin polarity identification: one is identification in circuit graphical symbols, and the other is physical identification of electronic components.

4. Printing of components themselves

        Generally speaking, printing represents certain parameters or models, including the manufacturer's batch number, version number, and other attributes. Some international certification symbols also exist. This method also depends on the level of understanding of component models and parameters. For example, a transistor like device labeled C1815 is a low-power low-frequency NPN type transistor; TL431 is an integrated voltage stabilizing IC; If labeled 13001, it is a low-power switch tube that can be used in small low-power chargers.

5. Examples of electronic component identification

        (1) Capacitor: Represented by "C", it is a letter of English CAPACITOR. According to polarity, capacitors can be divided into non polarity and polarity.

        (2) Resistance: Represented by "R", it is the letter of RESISTOR in English.

        (3) Inductor: Inductance is made by winding insulated wires around the skeleton; Inductance is indicated by the letter "L". The value of an inductor is called the inductance, and the unit is "Henry (H)"; "Because the unit of" heng "is too large, it is often used as" milli heng (mH) "and" micro heng (uH). ".

        (4) Transformer: Transformer is a type of inductive device, which can be divided into boosting, reducing, and isolation coupling; The transformer is represented by the letter "T" (which is a letter of TRANSFORMER in English); There are two types of transformers: primary and secondary connectors, so attention must be paid to their operation.

        (5) Diode: Diode is represented by the letter "D", which can be divided into positive and negative electrodes, and cannot be inserted reversely.

        (6) Crystal oscillator: Crystal oscillator, also known as crystal oscillator, is a quartz wafer processed from quartz crystals to produce resonance at a certain frequency, represented by the English word "X",. Because the role of crystal oscillators is to stabilize the oscillation frequency, the important parameter of crystal oscillators is the resonance frequency.