MindMap Gallery Basic electronic components, connectors and wires
The mind map of Chapter 3 of Automation Basics Introduction and Preliminary Practice includes capacitors, resistors, potentiometers, inductors, transformers, etc.
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This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
This is a mind map about plant asexual reproduction, and its main contents include: concept, spore reproduction, vegetative reproduction, tissue culture, and buds. The summary is comprehensive and meticulous, suitable as review materials.
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
Basic electronic components, connectors and wires
3.1 Electronic components, connectors and wires are the basis of electronic circuits
3.2 Resistors and potentiometers
3.2.1 Resistors
1. Introduction to resistors
Resistance reflects the resistance of a conductor to current flow. The component that blocks current flow in a circuit is called a resistor, usually called a resistor. Represented by the letter R
2. Physical drawings and symbols of resistors
3. Classification of resistors
Resistors are divided into thin film, alloy, synthetic and sensitive types
4. Naming of resistors
5. Main parameters of resistors
The main parameters of the resistor include nominal value, allowable deviation, rated power, ultimate operating voltage, rated voltage, stability, noise electromotive force, maximum operating temperature, high frequency characteristics and temperature characteristics.
1. Nominal resistance R: The nominal resistance on the resistor is called the nominal resistance.
2. Allowable deviation: The maximum deviation range between the nominal resistance value and the actual measured value and the percentage of the ratio of the nominal resistance value.
3. Rated power P: At the specified temperature, the maximum power allowed to be consumed by long-term continuous operation in the circuit without damage or significant change in its performance.
4. Limit working voltage V: The voltage value that cannot be exceeded, otherwise it will burn out immediately.
5. Rated voltage U: U=min(PR**1/2, V)
6. Stability: the degree to which it is not affected by the environment and working conditions.
7. Noise electromotive force: The electric potential generated by thermal noise and current noise is generally considered for weak signal systems.
8. Maximum operating temperature: the maximum temperature at which the resistor can work normally.
9. High-frequency characteristics: Distributed inductance and parasitic capacitance exist in any kind of resistor. It is just a matter of size. The distributed inductance and parasitic inductance of wirewound resistors are much larger than those of non-wirewound resistors.
10. Temperature characteristics: The resistance of metals increases with temperature, while the opposite is true for non-metals, which have a negative temperature coefficient and decrease with temperature.
6. Identification of resistors
1. Direct marking method: The main parameters of the component are directly printed on the surface of the component. This method is mainly used for resistors with relatively large power.
2. Color coding method: The color coding method is widely used for low-power resistors. Generally, the color circle is used to represent the value and accuracy of the resistor. Three-color ring resistors do not provide deviation information, while four-color and five-color ring resistors provide deviation information. Resistors generally use a background to distinguish the type of resistor: for example, light colors (light green, light blue, light brown) represent carbon film resistors, red represents metal or metal oxide film resistors, and dark green represents wirewound resistors.
Black 0, Brown 1, Red 2, Orange 3, Yellow 4
Green 5, Blue 6, Purple 7, Gray 8, White 9
3. Text symbol method
7. Capacitor selection specifications
1. Power (1) When the ambient temperature where the resistor works is lower than the rated temperature, its actual power consumption must be less than 50% of the rated power; (2) When the ambient temperature where the resistor works is greater than the rated temperature, its actual power consumption must be less than the resistor power derating. The curve corresponds to 50% of the power limit
2. Surface temperature For resistors used for indoor controllers, the surface temperature of the resistors should be less than 80°C when tested at a voltage of 220V±15%, working condition 32°C, and humidity 80%; for resistors used for outdoor controllers, tested at a voltage of 220V±15 %, tested at 43°C and 80% humidity, the surface temperature of the resistor should be less than 90°C.
3. Working voltage (1) The maximum working voltage of the resistor should be less than its rated voltage.
4. Requirements for the use of strong current circuits (1) Under the conditions of strong current circuit use and the maximum temperature rise of the resistor in actual application is less than 15K, glass glaze resistors or metal glaze resistors must be used. Metal film resistors and oxide film resistors are prohibited. (2) In strong current circuits, when the temperature rise of the resistor is greater than 15K, an oxide film resistor should be used; when used across the zero live line, two oxide film resistors must be connected in series.
5. High frequency characteristics of resistors At low frequencies, the impedance is approximately equal to the resistance value; as the frequency increases, the capacitive reactance decreases and the inductive reactance increases. When the capacitive reactance is small, the inductive reactance plays a major role and the total impedance increases; the frequency continues to increase, and when it reaches the resonant frequency, the impedance is minimum. Equal to resistance; when exceeding the resonant frequency, the impedance will increase again.
8. How to judge the quality of resistors
(1) Check the appearance to see if the appearance is correct, the logo is clear, and the protective paint layer is intact. (2) Use a multimeter with an appropriate ohm range to measure the resistance of the resistor, and compare this value with the nominal resistance of the resistor to see if it meets the error range. Pay attention to disconnecting one end of the resistor from the circuit before measurement; pay special attention to the fact that when measuring high resistance values, it is not allowed to touch the test leads with your hands. (3) Accurate measurement of resistance requires the use of a bridge
3.2.2 Potentiometer
A potentiometer is an adjustable resistor and one of the most versatile components in electronic circuits. It has three lead-out ends, two of which are fixed ends and the other is a central shaft head. Rotate or adjust the rotary shaft of the potentiometer, and the resistance between the central shaft head and the fixed end will change.
1. Classification of potentiometers Usually potentiometers can be divided into different types according to different conditions. (1) According to the adjustment method: rotation (single turn, multiple turns), straight sliding. (2) According to the number of joints: single joint, double joint. (3) Press whether there is a switch: with switch (rotation, push-pull), without switch. (4) According to the output function characteristics, that is, the relationship between resistance value and operating quantity: linear (X/B) (D/C) - tone control; exponential (Z/A)
2. Structure and working principle of potentiometer The resistor body of the potentiometer has two fixed ends. By adjusting the rotating shaft or slide handle and changing the position of the movable contact on the resistor body, the resistance value between the movable contact and either fixed end is changed, thereby changing the voltage. with the size of the current. Taking the rotary potentiometer as an example, the potentiometer is mainly composed of a resistor, a sliding piece, a rotating shaft, a welding piece and a shell.
3. Main parameters of potentiometer (1) Nominal resistance: Nominal resistance, the same as resistance. (2) Rated power: In a DC or AC circuit, when the atmospheric pressure is 87~107kPa, at the specified rated temperature The maximum power allowed to be consumed by the long-term continuous load on the two fixed ends under the temperature. (3) Degree of compliance: The degree of compliance between the actual output function characteristics of the potentiometer and the required theoretical function characteristics. It is expressed as the maximum deviation between the actual characteristics and the theoretical characteristics as a percentage of the total applied voltage. (4) Resistance change characteristics: linear, logarithmic, exponential. (5) Zero resistance: the resistance at both ends when the movable contact slides to the fixed end. (6) Resolution (resolution): The theoretical accuracy of the potentiometer. Wirewound potentiometers and linear potentiometers: The change in resistance caused by each turn of the moving contact on the winding is related to the total resistance. It is expressed as a percentage of resistance, that is, the reciprocal of the total number of turns N of the winding. Potentiometer with functional characteristics: Since the resistance of each turn of the winding is different, the resolution is a variable. With function properties The section with the largest slope on the curve is used as the average resolution. (7) Sliding noise: Improper distribution of potentiometer resistance, improper coordination of the rotating system, and contact resistance of the potentiometer, etc. Causes noise superimposed on the signal. (8) Wear resistance: The total number of reliable movements of the movable contact of the potentiometer under the specified test conditions, commonly used "weeks" express.
4. Identification of potentiometer Potentiometers generally use the direct marking method, and letters and numbers are used to mark their models and ratings on the potentiometer shell. Power, nominal resistance, relationship between resistance and angle, etc.
5. Selection specifications for potentiometers The selection of potentiometers must also comply with the specifications for resistor selection, such as power, surface temperature, working voltage, strong current circuit usage environment, and high-frequency characteristics of the resistor. At the same time, note: Choose the appropriate resistance ratio according to the application; if high resolution is required, non-wirewound potentiometers and multi-turn potentiometers can be used; if no further adjustment is required after adjustment, use trimmer potentiometers. The main requirements for the potentiometer are that the resistance value meets the requirements, the contact between the center sliding end and the resistor body is good, the rotation is smooth, and for the switch potentiometer, the switch part should act accurately, reliably, and flexibly
6. Identification method and detection of potentiometer The following points need to be noted when detecting potentiometers: (1) Whether the mechanical parts are intact, making noise on and off, whether the rotation is smooth, etc.; (2) Measure whether the resistance between the fixed ends is consistent with the nominal resistance, and rotate the sliding contact at the same time, and it remains unchanged; Its value should be fixed (3) During the measurement process, slowly rotate the shaft. Under normal circumstances, the reading should change smoothly in one direction; Is the insulation resistance between each terminal, shell and rotating shaft large enough?
3.3 Capacitor
3.3.1 Introduction to capacitors
A capacitor consists of a layer of non-conductive insulating material (dielectric) sandwiched between two conductors close to each other. Electric current passes between capacitors in the form of an electric field. Capacitance is usually represented by the letter C. The basic unit of capacitance is Farad (F). The conversion is as follows: lF=10°mF=10°uF=10'nF=10'pF (3-4) For the determining formula of plate capacitance: C=eS/4πkd, where the electrostatic constant k=8.988×10N·m2/C2, and ε is the dielectric constant. The capacitance C of the capacitor reflects the energy storage capacity of the capacitor Q=CU. It can be seen that the capacitance size is related to the dielectric and the facing area and diameter.
3.3.2 Physical drawings and symbols of capacitors
3.3.3 Capacitor classification
Based on analytical statistics, capacitors can be classified in the following ways. (1) Classified according to structure: fixed capacitors, variable capacitors and trimmer capacitors. (2) Classification by electrolyte: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors, electrothermal capacitors and air dielectric capacitors, etc. (3) Classified by use: high-frequency bypass, low-frequency bypass, filtering, tuning, low-frequency coupling, small capacitors. High frequency bypass: ceramic capacitors, mica capacitors, glass film capacitors, polyester capacitors, glass glaze capacitors. Low-frequency bypass: paper capacitors, ceramic capacitors, aluminum electrolytic capacitors, polyester capacitors. Filtering: aluminum electrolytic capacitors, paper capacitors, composite paper capacitors, liquid tantalum capacitors. Tuning: Ceramic capacitors, mica capacitors, glass film capacitors, polystyrene capacitors. Low frequency coupling: paper capacitors, ceramic capacitors, aluminum electrolytic capacitors, polyester capacitors, solid tantalum capacitors. Small capacitors: metalized paper capacitors, ceramic capacitors, aluminum electrolytic capacitors, polystyrene capacitors, solid tantalum capacitors, glass glaze capacitors, metalized polyester capacitors, polypropylene capacitors, mica capacitors. (4) According to different manufacturing materials, they can be divided into: porcelain capacitors, polyester capacitors, electrolytic capacitors, tantalum capacitors, and advanced polypropylene capacitors, etc.
3.3.4 Naming
3.3.5 Main parameters
The main parameters of the capacitor are as follows. (1) Nominal capacitance: The capacitance marked on the capacitor is also serialized in a similar manner to the resistor. (2) Allowable deviation: deviation between actual capacitance and nominal capacity. Usually marked with an accuracy grade. Accuracy levels include 01 (1%), 02 (2%), I (5%), II (10%), III (20%), IV (-30%~ 20%), V (50%~-20 %), VI (-10%~100%), general capacitors are commonly used in grades 1, Ⅱ, and Ⅲ, and electrolytic capacitors are in grades I, V, and VI, which are selected according to the use. (3) Rated voltage: The highest effective DC voltage that can be continuously applied to the capacitor at the lowest ambient temperature and rated ambient temperature. It is generally marked directly on the capacitor shell. When the voltage across the capacitor reaches a certain level, the intermediate medium can also conduct electricity. This voltage is called breakdown voltage. Capacitor breakdown will cause irreparable and permanent damage. (4) Insulation resistance Rm: DC voltage is applied to the capacitor and leakage current is generated. The ratio between the two is called insulation resistance. The larger the value, the better. When the capacitance is small, it mainly depends on the surface state of the capacitor; when the capacity is >0.1μF, it mainly depends on the performance of the medium. (5) Time constant of capacitor: The time constant is introduced to properly evaluate the insulation condition of large-capacity capacitors. It is equal to the product RmC of the insulation resistance and capacity of the capacitor. (6) Frequency characteristics: As the frequency increases, the capacitance of general capacitors decreases. (7) Loss: The energy consumed by a capacitor due to heating per unit time under the action of an electric field is called loss. All types of capacitors have specified allowable losses within a certain frequency range. The loss of a capacitor is mainly caused by dielectric loss, conductance loss and the resistance of all metal parts of the capacitor. Under the action of DC electric field, the loss of the capacitor exists in the form of leakage conduction loss, which is generally small. Under the action of an alternating electric field, the loss of capacitance is not only related to leakage conduction, but also to the periodic polarization establishment process.
3.3.6 Identification
1. Direct marking method
2. Digital representation
3. Text symbol method
4. Color marking method
3.3.7 Purpose
coupling
filter
decoupling
energy storage
Tuning
3.3.8 Features
3.3.9 Selection specifications
Basic ideas for selecting capacitors: (1) Meet the requirements of electronic equipment for the main parameters of capacitors; (2) Choose a type that meets the circuit requirements; (3) Consider the outer surface and shape of the capacitor; (4) Choose the appropriate model according to different circuits and the frequency of signals in the circuit, reasonably determine the accuracy of the capacitor and the rated working voltage and capacity of the capacitor, try to choose a capacitor with a large insulation resistance, and consider the temperature coefficient and frequency characteristics and use. environment. The following is some common sense for capacitor selection: (1) Large-capacity capacitors are usually suitable for filtering out low-frequency interference noise; (2) Small-capacity capacitors are usually suitable for filtering out high-frequency interference noise; (3) Mica capacitors and high-frequency mica capacitors can be selected for harmonic circuits. Ceramic capacitors; (4) When blocking DC, mica capacitors, polyester capacitors, ceramic capacitors and electrolytic capacitors can be selected; (5) When making a filter, electrolytic capacitors should be selected.
3.4 Inductor
3.4.1 Introduction to inductors
An inductor is a component that can convert electrical energy into magnetic energy and store it. The structure of an inductor is similar to that of a transformer, but it has only one winding. An inductor has a certain inductance, which only blocks changes in current. If the inductor is in a state where no current is flowing through it, it will try to block the flow of current through it when the circuit is turned on; if the inductor is in a state where current is flowing through it, it will try to maintain the current flow when the circuit is off. Inductors are also called chokes, reactors, and dynamic reactors. Inductance is usually represented by the letter L, and the units of inductance are represented by Henry (H), millihenry (mH) and microhenry (μH). The unit conversion relationship is 1H=10² mH=10°μH
3.4.2 Objects and symbols
3.4.3 Classification
Inductors are classified as follows. (1) According to working characteristics: fixed and variable. (2) According to whether there is a magnetic core: hollow, magnetic core. (3) According to the installation form: vertical, horizontal, small fixed type. (4) Divided according to working frequency: high frequency and low frequency. (5) According to the application: antenna coil, oscillation coil, choke coil, filter coil, notch coil, deflection coil.
3.4.4 Magnetic beads
The magnetic bead is rated according to the impedance it produces at a certain frequency (100MHz), so its unit is 2. The higher the frequency, the greater the resistance, so it is usually used to absorb high frequencies. Ferrite is its main material. Magnetic beads have three parameters: initial magnetic flux, Curie temperature, and operating frequency (core material).
The connection and difference between inductors and magnetic beads: (1) The inductor is an energy storage component, while the magnetic beads are energy conversion (consumption) devices; (2) Inductors are mostly used in power supply filter circuits, and magnetic beads are mostly used in signal circuits for electromagnetic compatibility (electromagnetic) (3) Magnetic beads are mainly used to suppress electromagnetic radiation interference, while inductors are used in this area to focus on suppressing conductive interference. Both can be used to deal with EMC and electromagnetic interference (EMI) problems. There are two ways of EMI, namely radiation and conduction. Different ways use different suppression methods. The former uses magnetic beads and the latter uses inductors; (4) Magnetic beads are used to absorb ultra-high frequency signals, such as radio frequency (RF) circuits, phase locked loop (PLL) oscillation circuits, and ultra-high frequency memory circuits, all need to be in the power input part Add magnetic beads, and the inductor is an energy storage component used in LC resonant circuits, LC oscillation circuits and medium and low-frequency filter circuits, etc. Its application frequency range rarely exceeds 50 MHz; (5) Inductors are used for circuit matching and signal quality control. Generally, inductors are used for ground connections and power connections. Magnetic beads are used where analog ground and digital ground are combined, and magnetic beads are also used for signal lines. The size of the magnetic bead (specifically the characteristic curve of the magnetic bead) depends on the frequency of the interference wave that the magnetic bead needs to absorb. The data sheet of magnetic beads usually comes with frequency and impedance characteristic curves.
3.4.5 Inductor: Main parameters: 1. Self-inductance coefficient 2. Allowable deviation 3. Quality coefficient 4. Distributed capacitance 5. Natural frequency 6. Rated current 3.4.6 Identification of the inductor 3.4.7 Purpose of the inductor 3.4. 8 Selection specifications 3.4.9 Testing
3.5 Transformer
Single, three phase
Main parameters: 1. Operating frequency 2. Rated voltage 3. Rated current 4. Rated capacity 5. Voltage ratio 6. Transformation ratio 7. Efficiency 8. No-load current 9. Leakage inductance 10. No-load loss
3.6 Diode
Main parameters: (1) Maximum rectified current I1: refers to the maximum forward average current allowed to pass through the tube during long-term operation. Because the current passing through the PN junction will cause the tube to heat up, if the current is too large and the heat generated exceeds the limit, the PN junction will burn out. (2) Reverse breakdown voltage V: refers to the voltage value that can cause reverse breakdown of the tube. During breakdown, the reverse current increases sharply and the unidirectional conductivity of the diode is destroyed, and may even burn out due to overheating. The maximum reverse operating voltage given in general manuals is about half of the breakdown voltage to ensure safe operation of the relationship. (3) Reverse current 1: refers to the reverse current when the tube has not broken down. The smaller the value, the better the unidirectional conductivity of the tube. As the temperature increases, the reverse current will increase significantly, so pay attention to the effect of temperature when using diodes. (4) Interelectrode capacitance C: Interelectrode capacitance is a parameter that reflects the capacitance effect of the diode PN junction. When used in high frequency or switching conditions, the influence of inter-electrode capacitance must be considered. (5) Maximum (minimum) operating current (for voltage regulator tubes): When using, special attention should be paid not to exceed the maximum rectified current and maximum reverse operating voltage, otherwise the tube will be easily damaged. (6) Maximum operating frequency f: Due to the junction capacitance of the PN junction, when the operating frequency exceeds a certain value, its one-way conductivity will become worse. The f value of point contact diodes is high, above 100MHz; the f value of rectifier diodes is low, generally not higher than a few thousand hertz. (7) Reverse recovery time t: refers to the time required for the reverse current to decay from a large value to close to I when the diode suddenly reverses direction from conduction. This indicator is extremely important when the high-power switching tube works in a high-frequency switching state.
3.7 Other semiconductor discrete devices
Transistor: Main parameters of bipolar transistor (1) Common emission current amplification factor β: The β value is generally 20~200, which is the most important parameter characterizing the current amplification effect of the triode. (2) Reverse breakdown voltage value Uanceo: refers to the maximum allowable value of the voltage applied to both terminals c and e when the base is open circuit. It is generally tens of volts, and high-voltage and high-power tubes can reach more than kilovolts. (3) Maximum collector current Im: refers to the current when the β value drops to the specified allowable value due to excessive transistor 1 (generally refers to the 1. value when the β value drops to 2/3 of the normal value). When the actual pipe exceeds Iy during operation, it is not necessarily damaged, but the performance of the pipe will become worse. (4) Maximum tube loss Pm: refers to the maximum allowable power dissipation of the collector junction based on the maximum allowable junction temperature of the triode. In actual work, the product of 1 and Uc of the triode is smaller than the P value, otherwise the tube may be burned out. (5) Penetration current 1m0: refers to the current 1 flowing through the collector when the transistor base current 1=0. It indicates the extent to which the base is out of control of the collector current. The Iceo of a low-power silicon tube is about 0.1mA, the value of a germanium tube is 1,000 times greater than that, and the Iceo of a high-power silicon tube is on the order of milliamps. (6) Characteristic frequency: refers to the operating frequency corresponding to when the β value of the triode drops to 1. The actual working frequency of f is 100~1000MHZ. Correct use of semiconductor transistors (1) When using a triode, more than two parameters must not reach the limit value at the same time. (2) When welding, low melting point solder should be used. The pin leads should not be shorter than 10mm, the welding action should be fast, and the welding time of each pin should not exceed two seconds. (3) When the transistor is welded into the circuit, the base should be connected first, then the emitter, and finally the collector. When removing, do it in reverse order to avoid burning the pipe. Do not disconnect the base lead while the circuit is energized to avoid damaging the tube. (4) When using a transistor, it must be fixed first to avoid short circuit or poor contact due to vibration, and it should not be relied on Close to the heating element. (5) The power transistor should be equipped with a sufficiently large radiator.
3.8 Integrated voltage stabilizing circuit
3.9 Other commonly used devices
3.9.1 Optoelectronic devices 3.9.2 Piezoelectric devices 3.9.3 Speakers 3.9.4 Microphones
3.10 Connector
3.10.1 Connector 3.10.2 Communication connector
3.11 Wire