Knowledge of electronic components - resistors

※Resistance: The resistance of the conductor to the current is called resistance, which is represented by the symbol R, and the unit is ohm, kiloohm, and megohm, respectively represented by Ω, KΩ, and MΩ.
※Resistor model naming method: The model of domestic resistors consists of four parts (not suitable for sensitive resistors) ① Main name ② Material ③ Classification ④ Serial number
※Classification of resistors: ①Wire wound resistors ②Film resistors: carbon film resistors, synthetic carbon film resistors, metal film resistors, metal oxide film resistors, chemical deposition film resistors, glass glaze film resistors, Metal nitride film resistors ③ solid resistors ④ sensitive resistors: piezoresistors, thermistors, photoresistors, force-sensitive resistors, gas-sensitive resistors, humidity-sensitive resistors.

※Resistor resistance marking method:
1. Direct marking method: Mark the resistance value on the surface of the resistor with numbers and unit symbols, and the allowable error is directly expressed as a percentage. If no deviation is noted on the resistance, it is ±20%.
2. Text symbol method: Use the regular combination of Arabic numerals and text symbols to represent the nominal resistance value, and its allowable deviation is also expressed in text symbols. The number in front of the symbol indicates the integer resistance value, and the following number indicates the resistance value of the first decimal place and the resistance value of the second decimal place in turn. Character symbols representing allowable errors Character symbols: DFGJKM Allowable deviations are: ±0.5%±1%±2%±5%±10%±20%
3. Digital method: the method of marking the nominal value with three digits on the resistor. The numbers are from left to right, the first and second digits are effective values, and the third digit is the exponent, that is, the number of zeros, and the unit is Euro. Deviations are usually expressed in text symbols.
4. Color scale method: mark the nominal resistance value and allowable deviation on the surface of the resistor with bands or dots of different colors. Most foreign resistors use the color code method.
Black-0, Brown-1, Red-2, Orange-3, Yellow-4, Green-5, Blue-6, Purple-7, Gray-8, White-9, Gold-±5%, Silver-±10 %, colorless - ± 20%
When the resistance has four rings, the last ring must be gold or silver, the first two digits are significant figures, the third digit is the power number, and the fourth digit is the deviation.

When the resistance is five rings, the distance between the last ring and the first four rings is relatively large. The first three digits are valid figures, the fourth digit is the power number, and the fifth digit is the deviation.

Recognition of the resistance value of the chip resistor: (The resistance surface of the usual chip resistor is marked with numbers, or expressed by letters, and the method of resistance value is as follows.
1. The first and second digits represent the real number of resistance.
2. If the number at the beginning of the third digit is 0, it represents dozens of ohms (between 10 and 99 ohms): 100 is a 10-ohm resistor, and 990 is a 99-ohm resistor
3. If the number at the beginning of the third digit is 1, it represents several hundred Euros (between 100 and 999 Euros). Example: 101 is 100 Euros, 151 is 150 Euros, and 951 is 950 Euros
4. If the number at the beginning of the third digit is 2, it represents several thousand ohms (between 1000 and 9999 ohms). Example: 102 is 1K, 152 is 1.5K, 992 is 9.9K
5. If the number starting from the third digit is 3, it represents dozens of K (between 10K and 99K). Example: 103 is 10K, 223 is 22K, and 993 is 99K
6. If the number starting from the third digit is 4, it means hundreds of K (between 100K and 999K). Example: 104 is 100K, 204 is 200K, 854 is 850K
7. If the number starting from the third digit is 5, it represents a few M (between 1M and 9.9). Example: 105 is 1M, 155 is 1.5M\\955 is 9.5M
8. If the number starting from the third digit is 6, it means ten M (between 100K~999K) Example: 106 is 10M\\566 is 56M
9. The standard method for four numbers is that the first three digits are real numbers, and the fourth digit is a multiple. 1001 is 1K, 1002 is 10K, and 1005 is 10M

Knowledge of electronic components - capacitors
※Capacitance: It is a physical quantity that characterizes the ability of a capacitor to hold charges. We increase the potential difference between the two plates of the capacitor by 1 volt, which is called the capacitance of the capacitor. The symbol for capacitance is C. Capacitors are one of the electronic components widely used in electronic equipment, and are widely used in DC blocking, coupling, bypass, filtering, tuning loops, energy conversion, control circuits, etc. Use C to represent capacitance, and the capacitance units include farad (F), microfarad (uF), picofarad (pF), 1F=10*6uF=10*12pF
1 farad (F) = 1000000 microfarad (μF) 1 microfarad (μF) = 1000 nanofarad (nF) = 1000000 picofarad (pF)

※Capacitor model naming method: The model of domestic capacitors generally consists of four parts (not applicable to pressure-sensitive, variable, and vacuum capacitors). Respectively represent the name, material, classification and serial number in turn.

※How to judge the polarity of the electrolytic capacitor: use a multimeter to measure it. Discharge the electrolytic capacitor first, and then connect the test leads to both ends. The negative terminal of the capacitor is the opposite of the digital meter, and, between measurements, the capacitor must be discharged. (2) Use the length of the pins to distinguish the positive and negative poles. The long pin is positive, and the short pin is negative; the black block with a mark on the capacitor is negative. There are two semicircles on the capacitor position on the PCB, and the pin corresponding to the colored semicircle is the negative pole.

※Classification of capacitors:
According to its polarity, it is divided into two categories: polarized capacitors (such as electrolytic capacitors) and non-polarized capacitors.
According to the structure, it can be divided into three categories: fixed capacitors, variable capacitors and trimmer capacitors.
Classified by electrolyte: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors and air dielectric capacitors.
According to the purpose, there are: high-frequency bypass, low-frequency bypass, filtering, tuning, high-frequency coupling, low-frequency coupling, and small capacitors.

※Capacitor capacity mark:
1. Direct marking method: mark directly with numbers and unit symbols. For example, 01uF means 0.01 microfarads, and some capacitors use "R" to represent the decimal point, such as R56 means 0.56 microfarads.
2. Text symbol method: use a regular combination of numbers and text symbols to represent capacity. For example, p10 means 0.1pF, 1p0 means 1pF, 6P8 means 6.8pF, and 2u2 means 2.2uF.
3. Color scale method: use color circle or color point to represent the main parameters of the capacitor. Capacitors are color coded in the same way as resistors.
Capacitor deviation symbol: +100%-0--H, +100%-10%--R, +50%-10%--T, +30%-10%--Q, +50%-20% --S, +80%-20%--Z.

※ Commonly used capacitors: aluminum electrolytic capacitors, tantalum electrolytic capacitors, film capacitors, ceramic capacitors, monolithic capacitors, paper capacitors, trimmer capacitors, ceramic capacitors, glass glaze capacitors, mica and polystyrene dielectric capacitors.

Knowledge of electronic components - inductors
※Inductor: The inductance coil is made of wires wound round by round on the insulating tube. The wires are insulated from each other, and the insulating tube can be hollow or contain iron core or magnetic powder core, referred to as inductance. Although they are not used much in electronic production, they are equally important in circuits. An inductor, like a capacitor, is also an energy storage element that converts electrical energy into magnetic field energy and stores energy in the magnetic field. The inductor is represented by the symbol L, and its basic unit is Henry (H), and millihenry (mH) is commonly used as the unit.

※Classification of inductors:
Classified by inductance form: fixed inductance, variable inductance.
According to the winding structure classification: single-layer coil, multi-layer coil, honeycomb coil.
Classified according to the nature of the magnetic conductor: air core coil, ferrite coil, iron core coil, copper core coil.
Classified according to the nature of work: antenna coils, oscillating coils, choke coils, trap coils, deflection coils.

※ Functional characteristics of inductors: It often works together with capacitors to form LC filters, LC oscillators, etc. In addition, people also use the characteristics of inductance to manufacture choke coils, transformers, relays, etc.; the characteristics of inductors are just the opposite of those of capacitors, which have the characteristics of preventing the passage of alternating current and allowing direct current to pass through.

There are many inductance coils on the radio, almost all of which are hollow coils wound with enameled wires or wound on skeleton magnetic cores and iron cores. There are antenna coils (which are wound on magnetic rods with enameled wires), intermediate frequency transformers (commonly known as Zhongzhou), input and output transformers, and so on.

※ Commonly used inductors: single-layer coils, honeycomb coils, ferrite cores and iron powder core coils, copper core coils, color code inductors, choke coils (choke coils), deflection coils

※Transformer: It is composed of an iron core and a copper coil wire wound on an insulating frame. The insulated copper wire is wound on the plastic skeleton, and each skeleton needs to be wound with two sets of input and output coils. The middle of the coil is isolated with insulating paper. After winding, insert many iron core sheets in the middle of the plastic skeleton. This can significantly increase the inductance of the coil. A transformer uses the principle of electromagnetic induction to transfer electrical energy from one of its windings to the other. The transformer has an important function in the circuit: to couple the AC signal to block the DC signal, and to change the voltage ratio of input and output; to use the transformer to make the impedance at both ends of the circuit well matched to obtain the maximum transmission signal power.

※Relay: It is an electronic mechanical switch. It uses enamelled copper wire to wind hundreds to thousands of circles on a round iron core. When the current flows through the coil, the round iron core generates a magnetic field, and the round iron core The iron plate with the contact piece is sucked, so that it disconnects the first contact and connects the second switch contact. When the coil is powered off, the iron core loses its magnetism, and due to the elastic action of the contact copper sheet, the iron plate leaves the iron core and restores the connection with the first contact. Therefore, a small current can be used to control the switching of other circuits. The entire relay is protected by a plastic or plexiglass dust cover, and some are fully sealed to prevent electrocution and oxidation.

Knowledge of electronic components - semiconductor devices
※Semiconductor: It is a substance with special properties. It is not completely conductive like a conductor, and it is not conductive like an insulator. It is in between, so it is called a semiconductor. The two most important elements in semiconductors are silicon (pronounced "gui") and germanium (pronounced "zhe").

※Semiconductor classification: Semiconductors are mainly divided into diodes, triodes, thyristors, and integrated circuits.

※Classification of diodes: Zener diodes for voltage stabilization, switching diodes for digital circuits, varactor diodes for tuning, and photodiodes, etc., the most common ones are light-emitting diodes, rectifier diodes... Diodes are in the circuit It is represented by "D"; the light-emitting diode is represented by "LED"; the Zener diode is represented by "Z".

※Diode polarity discrimination:

(1) Ordinary diodes: Generally, the polarity is marked on the outer shell of the diode. Most use a ring of a different color to indicate the negative pole, and some are directly marked with a "-".

(2) The polarity of the light-emitting diode can be judged from the internal structure of the pin and the tube. If the pin is not cut, it is generally believed that the long pin of the light-emitting diode is the positive pole, and the short pin is the negative pole. The polarity discrimination of electrolytic capacitors is consistent. From the perspective of the internal structure of the die, the die is composed of two parts, a large and a small petal. There is a conical pit on the large petal to concentrate light and improve brightness. The two petals are connected together by a thin metal wire in the middle, which is connected to the small petal part of the die. It is connected to the long-leg positive pole, and the short-leg negative pole is connected to the large petal part of the tube core. (3) Judging by the ohm range of the multimeter, the resistance value is small when the forward conduction is conducted, and the anode of the diode is connected with the black test lead. The jingle is called "Black Small Positive, Red Big Negative".

※Detection of ordinary diodes: The polarity of the diode is usually marked on the shell, if there is no mark, it can be judged by measuring the forward and reverse resistance of the multimeter resistance file (generally use R×100 or ×1K file)

※Detection of ordinary light-emitting diodes:

(1) Use a pointer multimeter with a ×10kΩ block to roughly judge whether the light-emitting diode is good or bad. Normally, the forward resistance of the diode is tens to 200kΩ, and the reverse resistance is ∝. If the forward resistance value is 0 or ∞, and the reverse resistance value is small or 0, it is easy to be damaged. This detection method cannot actually see the luminescence of the luminescent tube, because the ×10kΩ block cannot provide a large forward current to the LED.

(2) Using a 3V regulated source or two dry batteries in series and a multimeter (either pointer or digital) can accurately measure the optical and electrical characteristics of light-emitting diodes. To this end, the circuit can be connected as shown in Figure 10. If the measured VF is between 1.4 and 3V, and the brightness of the light is normal, it means that the light is normal. If VF=0 or VF≈3V is measured and there is no light, it means that the luminescent tube is broken.

※Detection of infrared light-emitting diode: due to the infrared light-emitting diode, it emits 1~3μm infrared light, which cannot be seen by human eyes. Usually, the emission power of a single infrared light-emitting diode is only a few mW, and the angular distribution of the luminous intensity of different types of infrared LEDs is also different. The forward voltage drop of infrared LED is generally 1.3 ~ 2.5V. It is precisely because the infrared light emitted by it is invisible to the human eye, so the detection method using the above-mentioned visible light LED can only determine whether the forward and reverse electrical characteristics of its PN junction are normal, but cannot determine whether its luminescence is normal or not. For this reason, it is best to prepare a photosensitive device (such as 2CR, 2DR silicon photocell) as a receiver. Use a multimeter to measure the change of the voltage across the battery. To judge whether the infrared LED emits infrared light after adding an appropriate forward current. Its measurement circuit is shown in Figure 11.

※Triode: A triode is an electronic component composed of two PN structures into three poles, the base (B), the collector (C), and the emitter (E).

※Function of the triode: The triode mainly plays the role of current amplification and switching in the circuit; it also plays the role of isolation.

※Transistor naming: Chinese semiconductor device model naming method

The semiconductor device model consists of five parts (field effect devices, semiconductor special devices, composite tubes, PIN tubes, and laser devices are only named after the third, fourth, and fifth parts).
The first part: use numbers to represent the number of effective electrodes of semiconductor devices. 2-diode, 3-transistor
The second part: use Chinese pinyin letters to indicate the material and polarity of semiconductor devices. When representing a diode: A-N type germanium material, B-P type germanium material, C-N type silicon material, D-P type silicon material. When representing a triode: A-PNP type germanium material, B-NPN type germanium material, C-PNP type silicon material, D-NPN type silicon material.
The third part: Indicate the internal shape of semiconductor devices with Chinese pinyin letters. P-ordinary tube, V-microwave tube, W-regulator tube, C-parameter tube, Z-rectifier tube, L-rectifier stack, S-tunnel tube, N-damping tube, U-photoelectric device, K-switch tube , X-low-frequency low-power tube (F<3MHz, Pc<1W), G-high-frequency low-power tube (f>3MHz, Pc<1W), D-low-frequency high-power tube (f<3MHz, Pc>1W), A-high-frequency high-power tube (f>3MHz, Pc>1W), T-semiconductor thyristor (controllable rectifier), Y-body effect device, B-avalanche tube, J-step recovery tube, CS-field effect tube , BT-semiconductor special device, FH-composite tube, PIN-PIN tube, JG-laser device.
Part 4: Use numbers to represent the serial number Part 5: Use Chinese pinyin letters to represent the specification number

For example: 3DG18 means NPN type silicon material high frequency triode

※Classification of triode
1) According to material and polarity, there are silicon/germanium