Common devices on the circuit board include: resistance, capacitance, diode, triode, thyristor, touch switch, liquid crystal, light emitting diode, buzzer, various sensors, chips, relays, etc. Moreover, electronic components have different packaging types. The shapes of different types of components are the same, but the internal structure and uses are very different. For example, the components packaged in to220 may be triode, thyristor, field effect transistor or double diode. The components encapsulated in TO-3 include triode, integrated circuit, etc. There are several packages for diodes, including glass package, plastic package and bolt package. How to identify them? Xiaobian, let’s have a look.
Shape recognition method
The shape recognition of electronic components is the correspondence between the physical object and the name. Its purpose is to get an electronic component, know what it is and its circuit graphic symbols. As shown in the figure, there are three kinds of physical drawings of electronic components:
↑ outline physical drawing
Circuit graphic symbol recognition
Understanding the identification information in circuit graphic symbols is helpful to the memory of circuit symbols and the analysis of circuit working principle. The following points are mainly explained about identifying the graphic symbols of electronic components and circuits.
(1) The circuit graphic 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 graphic symbols. If the pins have positive and negative polarity, there will also be various expressions in the circuit graphic symbols.
(2) Component circuit graphic symbols have the characteristics of visualization. Each stroke or symbol of circuit graphic symbols expresses specific drawing information.
(3) The letter in the circuit graphic symbol is the first letter of the English word of the component. For example, the transformer is represented by T, which is the first letter of the English transformer. If you know professional English, it is also helpful to identify the circuit graphic symbols in the circuit diagram, which is very beneficial to the understanding of some circuit diagrams.
Pin identification and pin polarity identification
The pins of many electronic components have polarity, and each pin cannot be substituted for each other. At this time, it is necessary to identify the pins and pin polarity through circuit graphic symbols or physical components.
There are two methods of pin identification and pin polarity identification: one is the identification of circuit graphic symbols, and the other is the physical identification of electronic components.
Printing of components
Generally speaking, printing indicates some parameters or models. Of course, it also has attributes such as manufacturer’s batch number and version number. Some international certification symbols also exist. This method also depends on the usual understanding of component models and parameters. For example, a transistor like device marked c1815 is a low-power low-frequency NPN transistor; TL431 is an integrated voltage stabilizing IC; If marked 13001, it is a small power switch tube, which can be used in small small power chargers.
Examples of electronic component identification
(1) Capacitor: represented by “C”, it is the first letter of English capacitor. Capacitors can be divided into non polarity and polarity according to polarity. The circuit symbol is:
↑ capacitor circuit symbol
(2) Resistance: indicated by “R”, it is the first letter of English restor.
(3) Inductor: inductance is made by winding insulated wires on the skeleton; Inductance is represented by the letter “L”. The value of inductor is called inductance, and the unit is “Henry (H)”; Because the unit of “Heng” is too large, it is often used as “milliheng (MH)” and “micro Heng (Uh)”.
(4) Transformer: transformer is a kind of inductive device, including step-up, step-down and isolation coupling; The transformer is represented by the letter “t” (the first letter of English transformer); The transformer can be divided into primary connector and secondary connector, so it must be paid attention to when acting. The symbols are as follows:
↑ transformer symbol
(5) Diode: the diode is represented by the letter “d”, which can be divided into positive and negative, and it cannot be inserted reversely.
(6) Crystal oscillator: crystal oscillator, also known as crystal oscillator, is a quartz wafer processed with quartz crystal to produce resonance at a certain frequency, which is represented by “X” in English,. Since the function of crystal oscillator is to stabilize the oscillation frequency, the important parameter of crystal oscillator is the resonance frequency.
The above is the introduction of component identification on the circuit board. Due to the reasons of technology, manufacturer and manufacturer, the same electronic component will have different shapes, structures and materials, so we should learn as much as possible, which will be of great help in the future.


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