Saturday, January 1, 2011

Weak current College】 【electronic engineer the prerequisite knowledge (2)】.

<br> Conductor, electrical easier through objects. Insulators, harder to pass objects. Conductors and insulators and no obvious medium, conductor and an insulator is conductive capacities vary many many times the two objects in relative terms. <br> <br> Many .objects, they are common in different physical conditions (temperature, electric and magnetic fields, lighting, doping, etc), rendered out different conducting State. We call this type of object as the semiconductor. <br> <br> There are now conductor ., insulators and semiconductors, can produce a wide variety of electronic components, we can facilitate simple detection and use of energy. <br> Switch is actually a short circuit and open circuit is a resistance in zero ohm and infinity two resistance on the transform element ., this effect with tap switch and the same principle. <br> <br> At any time, as long as the current flows, there must be a closed path. This pathway that current loop. Do not consider the internal power supply, electric .current must flow from the cathode electrode. <br> <br> Power equivalent to a special electronics, has closed access talent to produce electricity. No conductor and other electronic components into a closed path does not have current. <br> <br> .No loop must have current, there must be a current loop. (AC current and does not require a physical path, vacuum, air can form a current loop.) <br> <br> Two different watermark one poor water, water pressure. .There is a water pipes, water will flow, water flow will be resistance. Pipe thinner, the greater the resistance, the smaller the flow; water pressure higher, a fluent greater. Voltage refers to two objects of electric potential difference between that voltage. .If the voltage between a conductive path, the path inside the current. Resistance, the larger the current smaller; the higher the voltage, the electric current. <br> <br> Pressure, flow, water resistance. Water flow is in the direction .of the flow from high to low (not pumping machine); parable of the corresponding power: voltage, current, and resistance. Electron flow is in the direction of the flows from positive and negative (no power). <br> <br> .Two water level between the water level difference is equal to the water pressure; two electrode electric potential difference between equals the voltage. High water level equivalent to the positive electrode, low water level equivalent to the negative electrode. <br> <br> Resistors ., capacitors, diodes and other components have two pins, these components use process, must follow certain rules of the PIN. <br> <br> Transistor as a resistance to being master of resistors, it will be the collector of the transistor and the .emitter of the two feet is equivalent to a resistor, the base up master role. <br> <br> All electronics are two basic approaches to parallel connection: parallel circuit voltage is equal on both sides. Series: in-circuit current is equal .. <br> <br> Parallel and series is the most basic circuit connection, no matter how complex circuit can be broken down into basic parallel and series, all the electronic components are also because the parallel and serial connection to form the current loop. .<br> <br> Resistance of resistance is greater and smaller, equivalent to a water pipe to widen the access road, water resistance smaller; resistance, the greater the resistance is more conspiracy, equivalent to the water longer longer, pathways, and water .resistance. <br> <br> Measurement voltage must be parallel to the voltmeter in need to test on both ends of the voltmeter exist internal resistance consumes little current to keep the pointer deflection. Generally, the larger ammeter to negligible. <br> < .br> Measuring current when the ammeter series in need test circuit (disconnect loop), starting from the current ammeters small impediment. Generally, the internal resistance is smaller to the ammeter. <br> <br> Power is an ability to maintain two test .point voltage appliance, it is the city that is the battery, can be to a capacitor windings. <br> <br> The battery provides power voltage polarity is long-term fixed, we called the DC. Frequently used batteries rated voltage of each .section is 1.5V. <br> <br> Power supply of electrical energy is positive and negative, on the occasion of the turn of the transform. That's because generator coil is in the cycle of and magnetic fields do relative motion, if you install .the current commutator DC can be issued. <br> <br> AC is no distinction between positive and negative pole, AC in the zero line and FireWire in positive and negative polarity, voltage, and other parts of the performance is the same, is .fully symmetrical. <br> <br> Mains voltage is 220V50Hz, mean effective voltage of 220V, per second, oriented to transform 50 times. Note: the number of Hz will transform how many times. <br> <br> Recommend beginners use .12V electronic production of the following, this cost is relatively low, low voltage, error in case of docking, burned components for electronic components likely to be small. The lower the voltage, the more secure (and less damage to electronic components) <br .> <br> In a few large electronics systems often have a very thick wire access now. However, electronic technology often say the Earth is not really required to receive Earth wire. <br> <br> Electronic technology is often said of the Earth .or ground often and the Earth is no relationship. Electronic line ground wire refers to the DC, AC or various signals share the part of the current loop. <br> <br> That a certain number of altitudes of the mountain, that a sea .level reference point for the public. Said at one point voltage level, it is necessary to find an equivalent to sea level reference point, such that the ground wire in electronic circuit diagram. <br> <br> Now most of the time, power .is the negative signals share the most part of the current loop, usually in the negative as ground power supply. Then, if a component's foot power said the cathode, the symbol PIN to ground. <br> <br> Is our hypothetical, public .a voltage reference point. In more complex circuit, Often may have more than one group of power, but also may select more than one reference point, then there may be some, these sites are not necessarily connected. <br> <br> Coupling ., bypass, decoupling three words are transmitted signal, the signal to provide access. Including coupling refers to the level before and after, bypass, passing between decoupling refers to the need to provide the signal path between (internal use per level). <br .> <br> Provides signaling pathway also that constitute the current loop. No current loop does not have a current, any circuit analysis is built on the analysis of the current loop. <br> <br> Equivalent circuit diagram that has the same effect .as the circuit diagram. Our analysis of the circuit diagram, the need to simplify complex circuit, this helps to expand the idea of simplifying the problem. <br> <br> Equivalent circuit diagrams are omitted in a condition, several didn't affect .electronic components. An example of a condition: analysis of DC, capacitor as open circuit; analysis of AC, the capacitor as a short circuit. Inductance and capacitance is exactly the opposite. <br> <br> Capacitance and inductance on different frequency of .alternating current (AC DC as 0Hz) have different blocking effect, to a certain conditions, can be viewed as resistance, and the ability to calculate impedance value. <br> <br> Life of feedback refers to something results back, and then to .decide a matter. Cases, customer feedback TV power consumption, manufacturers will be improved. Electronic technology feedback is the output of the signal out and sent to the input. <br> <br> Positive feedback is an output signal if larger, feedback to .the input, so that the output signal change; output signal if smaller, feedback to the input, so that the output signal changes. <br> <br> Negative feedback is exactly the opposite, the output signal if larger, feedback to the input ., so that the output signal becomes small; output signal if smaller, feedback to the input, so that the output signal. <br> <br> Positive feedback is usually used to produce the oscillation signal, the negative feedback is often used for stable .DC operating point. In exceptional circumstances (magnification enough), positive feedback can not oscillating, negative feedback but oscillation. <br> <br> Positive temperature coefficient of resistance of the thermistor is with temperature but increased the negative temperature coefficient is the resistance with .temperature rising to decrease. A bit like the positive and negative feedback, enter the temperature signal to determine the resistance value. <br> <br> In the electronic circuit, can be used to specify a range of positive and negative voltage represent daily life .there are none, light off, switch the second value, such as relative, which positive and negative voltage that high level and low level. <br> <br> Digital inputs and outputs are high level and low level, digital circuit is based on .several binary relations for logic to get the new binary results; binary is 0 and 1 two digits to represent all of the quantity. <br> <br> Digital circuits that specifically to these digital signal circuit or circuits. Learning digital circuit we suggest that .you first understand the binary. <br> <br> Binary number with 0 and 1 representative's digital circuits in binary (low level and high level), with 0 and 1 instead of me all the signals. <br> <br> Analog signal .is a positive and negative voltage change signals, it should try to avoid changes to the positive and negative voltage to the maximum value and minimum value, otherwise the signal may be distorted. <br> <br> D / A (/), A ./ D (mold / digital) converter is digital and analog circuits in close connection with the common approach. <br> <br> High-frequency circuit on very small capacitance, inductance very sensitive. Any wire, and conductors are equivalent to between inductance .and capacitance, inductance and capacitance. <br> <br> Work in the high frequency of electronic components, PIN length, distance are installed on circuit performance have the very tremendous influence. <br> <br> We are doing a few high- .frequency circuit (example FM wireless microphone, FM radio) parts of the experiment, remember that the connection to squat as far as possible, the symbol of the close-circuit board as possible. <br> <br> Each electronic component or a combination .of electronic components and their connections between symbols instead of that circuit schematic. You just remember all kinds of electronic component symbols and drawing rules will see circuit schematic. <br> <br> Have a good habits and experienced engineers carefully plotted out, often beautiful .layout reasonable, marking a clear, easy to read. When you can't read a circuit diagram, it is not necessarily your fault. <br> <br> Printed circuit board is circuit schematics to real change, is a product from the design .stage to the market penetration of. <br> <br> See printing plate figure than see schematics easy, as long as you understand the conductor and insulator and common electronic components, you can follow the printing plate in kind draw circuit schematics. <br .> <br> In the components more cases, have the circuit schematics on the printed circuit board for detection and repair is a very lucky. <br> <br> Own hands-on e-small production, maintenance or help others, then that .you set tired experience, the best time to learning technologies. Experience is accumulated. <br> <br> Very complex circuit or a sophisticated product, often need to use double-sided printed circuit board, multilayer circuit board. <br> <br .> Multi-layer circuit board except it can be distributed both inside and outside layers of wire, a middle-tier in Board also have wiring. Multilayer PCB except you can install the components of high density, you can enter the shield, the increase in .performance. <br> <br> In the circuit board to find a small resistance or small capacitor, not directly to find them, please find and they are connected to the transistor or integrated circuit, then find them, thus more quickly. <br .> <br> Observation on the circuit board components and copper cabling, observation of copper foil alignments, the ability to use light floods the look, the lamp is placed in a copper line. <br> <br> Capacitance is can hold power, .as if a containerInstall the water glass. Therefore, the capacitor can for charging and discharging, charge and discharge of the capacitor size now. <br> <br> Capacitance type, the most common is electrolytic capacitors (large capacity, there are positive and .negative), ceramic capacitors (capacity, without anode and cathode, temperature difference), polyester capacitor (polyester film capacitor, the capacity of small, good temperature characteristics). <br> <br> Ceramic capacitor of main parameters that capacity, special- .purpose high pressure of ceramic capacitors only logo out of the pressure resistance. Ceramic capacitor of use does not require seperate polarity, at both ends to arbitrary change. Ceramic capacitors are usually advised to work at high frequency. <br> <br> Inductance is .an electromagnetic conversion components, electric can produce magnetic, electro-magnetic can produce. Inductance in the magnetic field changes will produce a current of change; current changes will produce a magnetic field changes <br> <br> Inductor current and magnetic interactions always attempts .to hinder each other. Power transformer that use electromagnetic conversion process to finish blank mutual inductance. <br> <br> Inductance in the main function of the circuit have impacted the AC, DC; high-frequency AC resistance, low-frequency AC. .Inductance is commonly used in transformers, resonant circuit, and other purposes. <br> <br> Reverse voltage too high and forward current Exces may cause permanent damage, diode, diode and transistor damage mainly because power consumption is too large (reverse-voltage .breakdown instantaneous power consumption is very large) causes the PN physical damage. <br> <br> We can put transistors as resistance values can acquire a resistance, resistance range to near zero to infinity, changes in between. Therefore, the transistor can be .used to design amplifier and a switch circuit. <br> <br> Transistor has three tube pole, collector and emitter and the base. Base used to acquire other poles on the current role of obstacles. Analysis of current and voltage changes, and then .in the analysis of transistor working state. <br> <br> FET's role and the role of triode basically exactly the same. FET is usually the three pin, named source, drain and grid. Grid is used to acquire other poles on current obstacles .. <br> <br> Transistor is depend on the size of the base current changes to master other poles, rely on the FET gate voltage level changes to master other poles, FET gate basically does not require consumption current is able to master the addition .of two poles. <br> <br> FET is also divided into two types, n-channel and p-channel. However, field effect tube is voltage control devices, low power supply voltage is very difficult to play it's excellent performance <br .> <br> SCR three pins, anode, cathode, and have extremely (also known as gate). Master the pole is used to acquire other poles on the current role of coherent and broken. SCR on current master role can only be connected or .disconnected from the two States. <br> <br> SCR's main role that's used as a switch, this is a no mechanical contact, no spark, high speed electronic switches. Some books also called SCR for the thyristor. <br> <br .> There is a known film circuit integrated circuit (thick film IC and film), the integration process is the resistance and wiring in a piece of insulation Silicon surface production; whereas the transistor, diode is not spread in the silicon chip directly generated, just .install them in the surface, and then use a plastic encapsulated the whole circuit. <br> <br> And gate circuit corresponds to a multiplications circuit. Usually have two or more input. There are four basic rules: 1 × 1 = 1, .1 * 0 = 0 0 * 1 = 0, 0 × 0 = 0. To draw a 1 × 1 × 1 = 1, 1 × 1 × 0 = 0 1 * 0 * 0 = 0, 0 × 0 × 0 = 0 ., etc. <br> <br> Or door circuit corresponds to a addition circuit. Usually have two or more input. There are four basic rules: 1 + 1 = 1, 1 + 0 = 1, 0 + 1 = 1, 0 .+ 0 = 0. To conclude that 1 + 1 + 1 = 1, 1 + 1 + 0 = 1 1 + 0 + 0 = 1, 0 + 0 + 0 = 0, etc. <br> <br> Gate circuit corresponds .to a negation circuit, and only one input. A maximum of only two situations: 1 = 0, 0 = 1. <br> <br> Exclusive-or gate circuit logic are special, there are only two inputs. A maximum of only .four scenarios: 0 + 1 = 1, 1 + 0 = 1, 0 + 0 = 0, 1 + 1 = 0. <br> <br> NAND circuit is the result of the and gate, the negation or the gate circuit is .the result of the or gate negation, xnor gate circuit is exclusive-or gate negates the result. <br> <br>.

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