Literacy essential, basic knowledge of electronic components
Electronic engineering album 2014-09-19
Whether you are a radio enthusiast or a maintenance technician, can you name the small components on the circuit board and what they do? If you want to be a master of component (chip) level, it is necessary to master some related electronic knowledge.
For example, in the maintenance of a certain hardware, the resistance value of a certain resistance measured with a multimeter is infinite. Although it can be concluded that the resistance is damaged, because there is no circuit diagram for each board and various peripheral devices (only a few products have local circuit diagrams), the specific resistance value of the resistance when it is not damaged is not known, so it is impossible to replace the damaged components. But if you can understand the color ring mark on the resistor, you can know the nominal resistance value of the damaged resistor. It will not be a problem to replace it, and the fault will be eliminated naturally.
Such as the above, there are many cases, such as the correct selection of components and so on, the author will not list them one by one, the following author will talk about some very practical electronic knowledge, I hope everyone can take another step to the road of master. Note: it is better to read the following pictures.
1、 Voltage, current
Voltage and current are brothers. Current flows from the place with high voltage (bit) to the place with low voltage (bit). If there is current, it must be because of the existence of voltage, but the existence of voltage does not necessarily produce current. If there is only voltage but no current, it can be proved that there is an open circuit in the circuit (for example, there is a switch in the circuit). In addition, sometimes the measured voltage is normal, but the current measurement is not necessarily normal. For example, there is a slight short circuit phenomenon or the resistance value of a certain element increases. Therefore, the voltage value and current value must be combined for analysis in the maintenance. When testing unknown voltage or current with a multimeter, the gear must be set to the highest gear. If the value cannot be measured, the gear will be gradually lowered.
Note: the symbol of voltage is "V", and that of current is "a".
2、 Resistor
All kinds of materials have certain resistance to the current it passes through. This resistance is called resistance. The entity (element) with lumped resistance is called resistor (in short, conductor with resistance value). Its role in the circuit is very important, in the computer boards and peripherals in the number is also very large. Its classification is also diverse, if classified by use: current limiting resistance, step-down resistance, voltage divider resistance, protection resistance, start-up resistance, sampling resistance, decoupling resistance, signal attenuation resistance, etc.; if classified by shape and production materials, there are: gold film resistance, carbon film resistance, cement resistance, non inductive resistance, thermistor, varistor, pull wire resistance, patch resistor According to the power classification: 1 / 16W, 1 / 8W, 1 / 4W, 1 / 2W, 1W wait.
The above resistors are common resistors, so we must know the nominal method of their resistance value. Next, I will introduce the most common chip resistor on each board card in the computer host computer as an example (the other resistance nominal methods are the same): the nominal methods of chip resistor are number method and color ring method. First of all, there are three numbers XXX on the resistor. The first two digits are ten and one, and the last one is the x power of 10. The specific resistance value of this resistor is the double digits of the first two numbers multiplied by 10 to the x power ohm. For example, the resistance value of the resistor marked with 104 is 100000 ohm (i.e. 100k Ω), and the resistance value of the resistor marked with 473 is 47000 ohm（ Now let's talk about the color ring method. This nominal method is the most common among all the resistance nominal methods (the chip shape is relatively small). The common color ring usually has four rings. We define the gold or silver ring as the last ring, and the color of the first three rings corresponds to the corresponding numbers. After we know the number, we should read the resistance with the above-mentioned number method But we must first know what color represents what number, so we must remember such a formula - black, brown, red, orange, yellow, green, blue, purple, gray and white, which correspond to 0123456789, respectively. As for gold and silver, they represent 10-1 and 10-2 respectively. These two colors only indicate the error value in the four-color ring resistance, so we only need to understand it. I will also give two examples to illustrate, so as to understand the memory. For example, the resistance value of the resistor marked with brown black yellow silver ring is 100000 ohm (i.e. 100k Ω), and the resistance value of the resistance marked with yellow purple orange gold ring is 47000 ohm (47K Ω).
There is also a kind of five color ring resistor. This kind of resistor is some resistors with relatively small resistance value and relatively high precision. Because it is also used in computer peripherals, I will also introduce it: it is the penultimate ring with gold or silver. The first three color rings are 100 bits, 10 bits and 1 bit respectively. The last color ring is the error value. The specific resistance value of such a resistor is If the resistance of the resistor marked with brown purple green silver brown ring is 1.75 Ω.
There is only so much basic knowledge about resistance. It is only necessary to pay attention to the power of resistor when replacing. It is no problem to replace chip resistor with 1 / 4 or 1 / 8 resistor.
Note: most SMD resistors using digital method are black, and the symbol of resistance in the circuit is "R".
3、 Electricity