Basic knowledge of common electronic components

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Capacitance
Capacitors are commonly known as capacitors. It is composed of two metal motors sandwiched between a dielectric layer. So it has the ability to store charges. Therefore, in theory, it has a cut-off effect on the DC current, and the AC current can be passed, with the higher the AC frequency, it through the power of the stronger. The appearance of some commonly used capacitors is shown in Figure 1.

Figure (1)
Capacitance is one of the most widely used devices in electronic circuits. We use it to filter, separate straight, AC coupling, AC bypass, etc., also use it and inductor components together to form the oscillation circuit.
Classification of Capacitance:
Depending on the dielectric, there are many types of capacitors. Our common and commonly used capacitance mainly include:
Name
Advantages
Disadvantages
Main applications
Ceramic Chip Capacitor
Very small, high-frequency loss, high temperature resistance, low price
Small capacity
Universal application
polyester Capacitor
Small size, Large capacity
Electrolytic Capacitor
Extremely Large capacity
Aluminum electrolytic Capacitor leakage is large, the capacity is not accurate. Tantalum Electrolytic capacitor good performance but high price
Coupling, filtering
Mica Capacitor
Stable performance, high temperature resistance, high pressure. Good high frequency performance
High price
Light Emitting Diodes
Paper dielectric capacitance
Small size, large capacity, low price
Poor performance at high frequencies
In most electronic productions, we often use porcelain capacitors and electrolytic capacitors.
Depending on the structure, we call the capacitance fixed capacitance, which can be adjusted as adjustable or half-adjustable capacitance. The ordinary radio station is the use of variable capacitance.
We commonly use "C" in the circuit diagram to represent the capacitance, with the symbol of Figure 2 to represent the fixed capacitance, the symbol of Figure 3 to represent a half variable capacitance, figure 4 represents variable capacitance, figure 5 represents a double variable capacitance.

Electrolytic capacitor general capacity is larger, from 1UF to 10000UF are more common, it is a positive and negative components of the capacitor, in the use of the positive node high potential end, negative junction low potential, can not reverse. Electrolytic capacitors are divided into aluminum electrolysis, tantalum electrolysis, niobium electrolysis, the market is common in the first two, where tantalum electrolysis is often used by some audio enthusiasts for sound systems. Electrolytic capacitors We commonly use the symbolic representation of Figure 6.

Figure 6: Marking symbol for electrolytic capacitance
Main performance parameters of capacitance:
1, electric Jong called capacity. A parameter describing the capacitance size, in the unit "method (F)". In practical applications, the capacitance of "FA" is seldom seen, and we commonly use other expansion units: "Micro-Method" (ΜF) and "Skin Method" (PF). Its unit conversion formula:
1f=1,000,000μf (106μf) =1,000,000,000,000pf (1012pF)
2, withstand pressure. Also called rated operating voltage. It refers to the maximum voltage at its poles that can withstand long-term and reliable operation within the specified temperature range of the capacitor. The DC operating voltage and AC operating voltage are also distinguished. This indicator is, of course, the higher the better, in other performance, the same situation, the high pressure can directly replace the low-withstand pressure, and vice versa.
3, leakage resistance. The dielectric in the capacitor is not absolutely insulated, when on the DC power, more or less will have the passage of current, we call it leakage. When the leakage condition teaches large, the capacitance heat can even cause the capacitance damage.
Capacitance Dimensioning method:
In the practical application process, we often need to choose the capacitance and other parameters. Capacitance of the capacity labeling method is the same as the resistance, but also by direct standard method (Digital direct representation) and color standard method two. But there are some such differences to note in the direct labeling method:
1) We often see 7 such as 103,224 of such labels on porcelain capacitors. This does not mean that the capacitance is 103PF or 224PF. Its capacity should be: the first two digits plus the number of "0" represented by the 3rd digit. For example:

103=10*1000=10000pf
224=22*10,000=220,000pf=0.22μf
2) There is a positive and negative polarity on the electrolytic capacitor, generally there are 8 indicators shown. There is also a common method of identification: The electrolytic capacitance of the non-sheared leg, the long side of the leg is the positive. Electrolytic capacitors are generally used straight standard method, its capacity does not need conversion. Note that the pressure value and operating temperature are generally indicated under the capacity. See Figure 9.


Figure 8
Figure 9
Measurement of capacitance:
The general multimeter does not have a special measurement of capacitance capacity of the gear. In most cases, we measure some of the capacitance's characteristics in the following ways:
1) measure its leakage resistance. Leakage resistance Small is the leakage of large capacitance is not suitable for the circuit, because it not only on the performance of the line, and due to heat and other reasons, and even burst, it may affect the life of other components in the line. Therefore, we can use the multimeter of the high-impedance file measurement (1kω or 10kω) to measure, the measurement method and the same way of measuring resistance:
1. Place the multimeter in front of the eyes.
2, select the highest measuring gear, and zero.
3. Put the pen on the metal pin at both ends of the capacitor, and if the electrolytic capacitor is measured, the positive of the capacitor should be red, and the Black Watch will be connected to the cathode. Take care not to have the bare part of the body connected to the two poles of the capacitor at the same time.
4, observing the movement of the needle, the large capacity capacitance, the needle will be significantly to the 0-scale direction of the swing to the opposite direction, until the needle stability and then read the leakage resistance data. For porcelain capacitor, its leakage resistance should be close to infinity. For aluminum electrolytic capacitors, refer to the following data:
Capacitance withstand voltage
Leakage resistance Range (KΩ)
6V
6V
15V
30-40
25V
30-60
407
60-100
150V
150-200
300V
250-350
450V
300-400
When less than the range value indicates that the capacitance leakage is large, more than the better.
2) estimate the polarity of the electrolytic capacitor. The leakage resistance of electrolytic capacitor is measured in positive and negative direction, and the red Pen is connected with the positive electrode when the leakage resistance is large. The pin can also be measured against the resistance of the aluminum casing, at the end of the zero negative.
3) estimate capacitance capacity. For more than 1μf capacitance, you can measure the capacitance capacity by measuring the leakage resistance, the data is measured in the direction of the needle to the 0 scale swing amplitude, the larger the swing amplitude, the larger the capacitance capacity (first to exclude the possibility of internal short circuit). You can also compare the capacitance of a known capacity to obtain a more accurate value. Note: When capacitance is tested for the 2nd time, the discharge must be done first. For 1000μf below the resistance, can be directly short-circuit discharge, more than two feet can be inserted into the wet sponge, a few minutes after the short-circuit discharge. The larger the capacitance capacity, the longer the discharge time is required.
Capacitance in series and in parallel:
The series of capacitors (Fig. 10) and parallel (Fig. 11) are used to change the capacitance on the line. Contrary to resistance:


C1, C2
C1
Capacitance series
C2
Capacitor parallel
When the capacitance is used in parallel, the actual capacity on the line equals the sum of the capacitors. namely: C1=C1+C2
When capacitance is used in series, the actual capacity on the line is calculated as: c=1/(1/C1+1/C2)
Resistance
First, resistance and Ohm's law:
Resistors we used to call resistors. It is the most commonly used electronic component in electrical equipment.
The resistor exhibits the same resistance to both DC and AC power. This resistance is described by the mathematical formula of Ohm's law through the motion form:
I (current) =v (voltage)/R (resistor)
This formula shows that the current through the resistor on the line is inversely proportional to the resistance value, and the voltage that is added to both ends.
In the electronic circuit, we often use the English letter R or 1 symbol to indicate the resistance:

R
Second, the resistance in series and parallel:
1, the Resistance of the series (Fig. 2):

R1
R2
According to Moore's law, the current on the same line is fixed, and the voltage on both ends of a and b equals the sum of R1, R2, and the total Resistance (R) at both ends of a and b according to Ohm's rule:
R*i=r1*i+r2*i
So: r= "R1" +r2
Conclusion 1: The total resistance of resistors in series on line is equal to the sum of each series resistance value.
Conclusion 2: The total resistance of series resistors on the line is certainly greater than the resistance of any resistor in the line.
2, the Resistance in parallel (Fig. 3):

According to Moore's Law, the voltage at both ends of a and B in this line is the same as that of R1 and R2, while the total current is the sum of the current through R1 and R2 resistors respectively. So according to Ohm's law:
R*i=r1*i1=r2*i2
And: i= "I1" +i2
Can be launched: 1/R=1/R1+1/R2
Conclusion 1: A, b both ends total resistance (R): r= "R1" *r2/(R1+R2)
Conclusion 2: The total resistance value of the parallel line is smaller than the resistance of any shunt in the line.
According to the above characteristics, we often use resistors in the electronic circuit for voltage divider, shunt, filter, impedance matching and other work.
Three, the type of resistance:
In the practical application of electronic equipment, we classify the materials according to the resistance. Common types and performance characteristics are shown in table 1 below:
Kinds
Advantages
Disadvantages
Appearance
Carbon Film Resistor
Good stability and adaptability, and the price is cheap
Patent leather is green, blue grey, beige
Metal Film Resistors
Better performance than film resistance in all aspects, often used in precision equipment
High price
Patent Leather for Dark red
Wire Wound resistor
Accurate resistance, high power withstand
But not for high-frequency work.
Patent leather is black
Appearance See Figure 4.

Figure 4
can also be classified according to resistance characteristics. Not adjustable, we call it a fixed resistor. And can be adjusted, we call it an adjustable resistor. And the common such as radio volume adjustment, mainly applied to the voltage distribution, we call the potentiometer (Figure 5), will be described in another article.

Figure 5
In addition to the above mentioned, we will also use a number of special resistance elements. The characteristic of these resistive elements is that the resistance will vary according to some external factors. For example: the light affected by what we call photoresistors, by external pressure is the impact of pressure-sensitive resistors, as well as thermal, gas-sensitive, electrical sensitivity and so on. Here are some pictures of the relevant resistors (Figure 6):

Figure 6
Four, the parameters of the Resistance:
can also be classified according to resistance characteristics. Not adjustable, we call it a fixed resistor. And can be adjusted, we call it an adjustable resistor. And the common such as radio volume adjustment, mainly applied to the voltage distribution, we call the potentiometer (Figure 5), will be described in another article.

Figure 5
In addition to the above mentioned, we will also use a number of special resistance elements. The characteristic of these resistive elements is that the resistance will vary according to some external factors. For example: the light affected by what we call photoresistors, by external pressure is the impact of pressure-sensitive resistors, as well as thermal, gas-sensitive, electrical sensitivity and so on. Here are some pictures of the relevant resistors (Figure 6):

Figure 6
Four, the parameters of the Resistance:
For fixed resistors, the main parameter indicators are two: resistance, power.
Resistance: A mathematical expression describing the resistance of a resistor to a current, in ohms. We also use the Greek letter Ω as an indication. We also common to kω (thousand euro), MΩ (m) of the logo, the conversion formula is as follows:
1mω=1,000kω=1,000,000ω
In our practical application, we often see two types of resistance values: one is the number and unit directly labeled Way (7), the other is the use of color ring to mark the way of its resistance (8), we call the color standard method, it also divided into two types: 4-ring resistor and 5-ring resistor, the value of the reading method, The color-to-value relationship (see Figure 8):

7

See Figure 8
Power: The standard term is the rated power, refers to the resistance under certain conditions (pressure, temperature, etc.) for a long period of continuous work can be allowed to withstand the maximum power. Therefore, we must pay attention to the choice of resistance power in some circuits, otherwise, due to resistance problems caused by resistance damage, may even lead to damage to other components of the equipment. In practical applications, a large power resistor with the same resistance can be used instead of a small power resistance, but the other is to be considered carefully.
Other parameters:
Temperature coefficient: Describes the effect of resistance temperature on its resistance.
Error level: Describes the difference between the produced resistor and the nominal resistor.
Measurement of Resistance:
Use analog multimeter test resistor resistance, the general arrangement is as follows:
1) Put the table in front of the eyes, easy to observe.
2) Adjust the position of the meter to Ω, touch the two pens, and observe the movement of the needle. If you do not move, you need to detect if the gear is on "Ω" or if the pen is connected correctly.
3) Select the "Ω" gear. The general multimeter has "Rx1", "Rx10", "Rx100", "rx1k", "rx10k" and other stalls. When we choose, we should choose to have the pointer fall within the range of 3-30. When less than 3 o'clock, cut 1, when more than 30 o'clock, an increase in the gear.
4) Zero adjustment. When we start using and shifting gears, we need to adjust the "0" knob on the multimeter to place the hands on the "0" scale. This will ensure the accuracy of the multimeter measurement data.
5) for the measurement of fixed resistance, the pen is put in full contact with the two ends of the resistor respectively. The data is read from the front. The value of the resistor is obtained by multiplying the data by the number of the file position.
6) for the adjustable resistor, first measure the resistance of the fixed end according to the above method, so that the maximum resistance value of the resistor is obtained. Then move a pen to the moving end of the movement resistor, rotate or move the adjustment knob while observing, and pay attention to whether the needle is continuously changing, otherwise it may be that the resistance is in poor contact.
Measuring resistors with a digital table:
The basic process is the same as the simulation table, except that zero zeroing is required. In addition, the detection gear is different from the analog table, which requires you to more accurately fall within the range of the scale. Whether it's using that multimeter, we need to be aware of:
1) When measuring, it is not possible for the body to contact both ends of the resistor. This results in inaccurate measurements, and the greater the resistance, the greater the impact. Think about why?
2) to the resistance on the circuit board, first of all to solder open one end, and do not live measurement.

Basic knowledge of common electronic components