第2章 Application and Appreciation
Lesson One Electronic System Components & Electronic System
Text A: Electronic Components & Electronic Circuit System
Electronics, which study the design and application of electronic unit, is in the field of engineering and applied physics. Electronics usually study the generation and movement of current in electronic circuits, also the receiving and storage of electronic signal. If you are new to electronics and would like to try adapting published projects, or designing and building your own circuits, you need to have a small stock of components available. However, there is a very wide range of components and it can be difficult to know which ones you really need! I hope the list below will help you choose a sensible selection which is within your budget. Remember that circuits built on breadboard can be dismantled after use and the components can be re-used.
It is the usually cheapest to buy components by mail order and several suppliers are listed on the next page. Send for a catalogue first, even if you have to pay for it, because most catalogues include a great deal of useful information as well as listing part numbers and prices. Kits of assorted components may be available and this is a great way to start if you can afford the initial cost. Remember that you will need to organize storage for the components!
Essential components
These are the components used in most projects. The individual components are quite cheap, but the total cost of the whole set will be significant! One way to spread the cost is to add a few items from this list every time you buy the components for a particular project. Click on the titles for further information.
Resistors
A resistor restricts the flow of current, for example to limit the current passing through an LED. A resistor is used with a capacitor in a timing circuit.
Resistors may be combined in series and parallel to obtain extra values, for example 100kΩ and 220kΩ in series is 320kΩ which is close enough to 330kΩ.
Capacitors
A capacitor stores electric charge. A capacitor is used with a resistor in a timing circuit. Fluctuations and ripples superimposed on the rectified DC voltage (noticeable as a hum in a malfunctioning audio amplifier) can be filtered out by a capacitor. It means that it can also be used as a filter, to block DC signals but let AC signals pass.
High values: 1µF 63V, 10µF 25V, and 100µF 25V electrolytic with radial leads, 10 of each;220µF 25V and 470µF 25V electrolytic with axial leads, 3 of each.
Diodes
A device which only allows current to flow in one direction.
LEDs
A transducer which converts electrical energy to light. Red, yellow and green 5mm standard LEDs, 10 of each.
Transistors
A transistor amplifies current. It can be used with other components to make an amplifier or switch circuit. A transistor amplifies current. Transistors are made of materials, such as silicon or germanium, that are“doped” (have minute amounts of foreign elements added) so that either an abundance or a lack of free electrons exists.
Integrated Circuits (chips) and holds
It is not worth ordering other ICs at this stage unless you know they are needed for some of the projects you wish to try. If you are planning to solder circuits on stripboard or PCB you will also need 8-pin, 14-pin and 16-pin DIL sockets (chip holders), at least 10 of each.
Variable Resistors
Presets are cheaper than standard variable resistors but most have pins which are too large for breadboards. This type of variable resistor with 2 contacts (a rheostat) is usually used to control current. Examples include: adjusting lamp brightness, adjusting motor speed, and adjusting the rate of flow of charge into a capacitor in a timing circuit. For breadboard circuits it's probably the best to buy standard variable resistors and solder short single core 1/0.6mm wires onto them. The useful values are: 10k LIN, 100k LIN and 1MΩ LIN, buy 2 of each. A 1MΩ LOG potentiometer is useful too. Knobs are optional because it is easy to turn the spindles by hand. If you buy presets the horizontal style are the best, all presets are LIN.
Battery Clip
Clip for a 9V PP3 battery, buy 3 (or 10 if you plan to solder projects). Remember to buy a battery too!
Wire
Red and black 7/0.2mm stranded wire, one colour of single-core 1/0.6mm wire, 10m (or a reel) of each. If you are planning to build projects on breadboard, buy some single-core wires with extra colours, including red and black.
Crocodile Clips
Buy at least one standard crocodile clip to use as a heat sink when soldering. Miniature red and black crocodile clips (buy about 10 of each) are useful for making your own test leads using 7/0.2mm stranded wire.
Switches
Switches are not essential for breadboard circuits because you can make or break links with pieces of wire. The on/off switch from soldered projects can also be omitted if you are willing to unclip the battery instead. If you wish to buy a few switches the most useful types are push-to-make and miniature SPDT toggle switches, 3 of each.
Strip-board
Buy one large sheet (or two) and cut it up as required. You can cut it neatly to size using a junior hacksaw, cutting along the lines of holes is the easiest. For quickness you can break it over the edge of a workbench along the lines of holes - take care though because this needs a fairly large force and the edges will be rough. You may need to use a large pair of pliers to nibble away any jagged parts.
Avoid handling strip-board that you are not planning to use immediately because sweat from your hands will corrode the copper tracks and this will make soldering difficult unless you clean the board first.
Breadboard
A small breadboard is suitable for simple circuits with up to two ICs, but if you intend to build more complex circuits such as counters you'd better buy a larger breadboard. Breadboards do not require soldering so the components used on them can be re-used many times. They are ideal for testing your own circuit designs and trying out ideas such as adapting a published project.
Storage systems for components
You can store all your components in a single container, such as a plastic food box. But as you accumulate more items it will become increasingly difficult to find the smaller components! A cheap solution is to organize the parts into small snap-top plastic bags which can be labeled. In fact you may find that some components are supplied like this. Probably the best storage system is a cabinet of plastic drawers. These can be expensive, but you do not need many drawers because there is no need to have a drawer for every single component value. Many parts can be grouped together, such as decades of resistor values. For example you could organize a 15-drawer cabinet like this:
1. Resistors 10Ω+ (third band black) only a few, but they tend to be large
2. Resistors 100Ω+ (third band brown)
3. Resistors 1kΩ+ (third band red)
4. Resistors 10kΩ+ (third band orange)
5. Resistors 100kΩ+ (third band yellow)
6. Resistors 1MΩ+ (third band green) and 10MΩ (third band blue)
7. Presets, also variable resistors if they will fit in the drawer
8. Capacitors low values, less than 1µF
9. Capacitors electrolytic 1µF+
10. Diodes and transistors
11. LEDs and lamps (also LED clips and lampholders)
12. ICs (chips) and their holders (DIL sockets)
13. Switches and relays
14. Connectors (crocodile clips, plugs and sockets)
15. Other components (battery clips, piezo-transducers, LDRs, thermistors)
Block diagrams
Block diagrams are used to examine (and design) complete circuits by breaking them down into smaller sections or blocks. Each block performs a particular function and the block diagram shows how they are connected together. No attempt is made to show the components used within a block, only the inputs and outputs are shown. This way of looking at circuits is called the systems approach. Power supply (or battery) connections are usually not shown on block diagrams. Internal DC power supply is a transformer, which steps up or steps down the input voltage to a level suitable for the operation of the equipment.
Audio Amplifier System
The power supply (not shown) is connected to the pre-amplifier and power amplifier blocks.
· Microphone - a transducer which converts sound to voltage.
· Pre-Amplifier - amplifies the small audio signal (voltage) from the microphone.
· Tone and Volume Controls - adjust the nature of the audio signal.
· The tone control adjusts the balance of high and low frequencies.
· The volume control adjusts the strength of the signal.
· Power Amplifier - increases the strength (power) of the audio signal.
· Loudspeaker - a transducer which converts the audio signal to sound.
Radio Receiver System
The power supply (not shown) is connected to the audio amplifier block.
· Aerial - picks up radio signals from many stations.
· Tuner - selects the signal from just one radio station.
· Detector - extracts the audio signal carried by the radio signal.
· Audio Amplifier - increases the strength (power) of the audio signal.
· This could be broken down into the blocks like the Audio Amplifier System shown above.
· Loudspeaker - a transducer which converts the audio signal to sound.
Regulated Power Supply System
· Transformer - steps down 230V AC mains to low voltage AC.
· Rectifier - converts AC to DC, but the DC output is varying.
· Smoothing - smooth the DC from varying greatly to a small ripple.
· Regulator - eliminates ripple by setting DC output to a fixed voltage.
Feedback Control System
The power supply (not shown) is connected to the control circuit block.
· Sensor - a transducer which converts the state of the controlled quantity to an electrical signal.
· Selector (control input) - selects the desired state of the output. Usually it is a variable resistor.
· Control Circuit - compares the desired state (control input) with the actual state (sensor) of the controlled quantity and sends an appropriate signal to the output transducer.
· Output Transducer - converts the electrical signal to the controlled quantity.
· Controlled Quantity - usually not an electrical quantity, e.g. motor speed.
· Feedback Path - usually not electrical, the sensor detects the state of the controlled quantity.
New Words and Expressions
Notes
1. Fluctuations and ripples superimposed on the rectified DC voltage (noticeable as a hum in a malfunctioning audio amplifier) can be filtered out by a capacitor.
译文：我们可以用电容来滤除直流电源的纹波(表现为音频放大器的嗡鸣故障)。
2.Electronics, which study the design and application of electronic unit, is in the field of engineering and applied physics. Electronics usually study the generation and movement of current in electronic circuits, also the receiving and storage of electronic signal.
译文：电子学隶属于应用物理学，并与工程实现密切相关，主要研究电子单元的设计与应用，以及在电路中，利用电流产生，传输、接收和储存信息的过程。
3.Transistors are made of materials, such as silicon or germanium, that are“doped” (have minute amounts of foreign elements added) so that either an abundance or a lack of free electrons exists.
译文：半导体是将硅、锗材料进行加工，参入少量其他元素，产生自由电子和空穴。
4.Internal DC power supply is a transformer, which steps up or steps down the input voltage to a level suitable for the operation of the equipment.
译文：内部直流电源是一个变压器，它可以步进调节输入电压，使之等于设备的工作电压。
Exercises
1. Translating this paragraph into Chinese
The transistor, invented in 1948, has now almost completely replaced the vacuum tube in most of its applications. Incorporating an arrangement of semiconductor materials and electrical contacts, the transistor provides the same functions as the vacuum tube but at reduced cost, weight, and power consumption and with higher reliability. Subsequent advances in semiconductor technology, in part attributable to the intensity of research associated with the space-exploration effort, led to the development of the integrated circuit. Integrated circuits may contain hundreds of thousands of transistors on a small piece of material and allow the construction of complex electronic circuits, such as those in microcomputers, audio and video equipment, and communications satellites.
2. Translating this paragraph into English
运算放大器是模拟计算机的重要元件。模拟计算机可使几种数学运算用电子线路来实现。运算放大器可用来构成放大器的重要特征之一是放大器具有差分输入。这种输入结构可以产生信号之差并建立了虚地或两个输入端之间虚短的概念。虚短用于在一个节点上把几个电流信号相加而不影响其他输入电流信号。这些信号相加后易于变换为输出电压。
Text B: Briefly Introduction of Electronic Circuit Design
With the development of the transistor, electronic devices shrank tremendously, and transistorized pocket radios, for example, appeared. Then several other idea came along that enabled engineers to design still smaller units. There was the idea of the printed circuit. Instead of cutting and soldering wires to make circuits, the circuits were applied to an insulating base by a printing process using special conducting pastes for“ink” or by a metal plating and etching process. This eliminated numerous hand operations and made possible circuits smaller than that could be soldered by hand.
Next came the idea of depositing these circuits by evaporating the metal at high temperature in a vacuum. This is done by placing the insulating base, or substrate, into a special vacuum furnace. The substrate is first covered by a mask with slots and openings cut out so that the metal will be deposited through these openings onto the substrate. The air is evacuated from the furnace, the metal is heated, and it evaporates. It deposits as a thin film through the opening in the mask onto the substrate.
It soon became obvious that relatively complicated circuits could be built up by using a series of masks on the substrate, each designed to permit deposition of one part of the circuit. Furthermore, it soon became possible to deposit the passive parts of electronic circuits, such as the resistors and capacitors, by the same method.
In practice, sheets of substrate large enough to carry hundreds of identical circuits are prepared at one time. Then, the substrate is sliced up to separate the circuits. Each of these may be no more than a small fraction of an inch in size. Finally, the active elements, the diodes and transistors are attached by soldering.
A still more advanced technique produces what are called "integrated circuits".
A modern method of producing complete microminiature circuits in large quantity is to use paper-thin sheets of semiconductor material, the same general technique of masking is used. However, part of the thin-film deposition process does not put a layer of metal on the surface. Instead, it applies materials that diffuse into the semiconductor substrate itself, forming diodes and transistors within the substrate.
This technique is basically simple and can be made entirely automatic. In fact, one authority has said that it may be possible for a single machine to produce most of the electronic circuits needed in the entire world.
With these new methods of making electronic circuits we can be sure that the electronic devices of the future, or radios, television sets, telephones, and so on, will become quite small. They may be more complex inside to make them more useful to us, but they will be very simple to operate.
From a technological point of view, the small size of the electronic circuits is not the only or even the essential advantage of the techniques just described. What is more important is the great increase in circuit reliability, e.g. the increase in "mean time between failure" (MTBF), of the equipment. From an economic point of view, integrated circuits mean much lower costs through the use of automated mass production methods.
Electronic circuit design has traditionally fallen into two areas: analogue and digital. These subjects are usually taught separately, and electronics engineers tend to specialize in one area. Within these two groupings there are further specialization, such as radio frequency analog design. In addition, of course, software engineering plays an increasingly important role in embedded system and consumer goods. Cards have sophisticated control system. Many homes now have personal computer. Products that used to be thought of as analogue, such as radio, television, and telephones, are becoming digital. Digital compact discs have almost entirely replaced analogue LPs for recorded audio. With these changes, the lifetimes of products have lessened. In a period of less than a year, new models will probably have replaced all the digital electronic products in your local store.
To keep pace with this rapid change, electronics products have to be designed extremely quickly. Analogue design is still a special (and well-paid) profession. Digital design has become strongly dependent on computer-aided design(CAD) – also known as design automation(DA) or electronic design automation(EDA). The EDA tools allow two tasks to be performed: synthesis, in other words the translation of a specification or the detailed implementation can be exercised in order to verify correct operation. Synthesis and simulation EDA tools require that the design be transferred from the designer's imagination into the tools themselves. This can be done by drawing a diagram of design using a graphical package. This is known as schematic capture. Alternatively, the design can be represented in a textual form, much like a software program.Textual descriptions of digital hardware can be written in a modified programming language, such as C, or in a hardware description language (HDL). Over the past thirty years or so, a number of HDLs have been designed. Two HDLs are in common usage today: Verilog and VHDL (VHSIC Hardware Description Language, where VHSIC stands for Very High Speed Integrated Circuit). Standard HDLs are important because they can be used by different CAD tools from different tool vendors: in the days before Verilog and VHDL, every tool had its own HDL, requiring laborious translation between HDLs, for example to verify the output from a synthesis tool with another vendor's simulator.
The basic building blocks of digital circuits are gates. A gate is an electronic component with a number of input and, generally, a signal output. The inputs and the outputs are normally in one of two states: logic 0 or logic 1.These logic values are represented by voltages (for instance, 0 V for logic 0 and 3.3 V for logic 1) or currents. The gate itself performs a logical operation using all of its inputs to generate the output. Ultimately, of course, digital gates are really analogue components, but for simplicity we tend to ignore their analogue nature.
It is possible to buy a single integrated circuit containing, say, four identical gates. Two of the connections of the gate are for the positive and negative power supplies to the device. They are not normally shown in logic diagrams. A digital system could be built by connecting hundreds of such devices together – indeed many systems have been designed in that way. Although the individual integrated circuits might cost as little as 10 cents each, the cost of designing the printed circuit board for such a system and the cost of assembling the board are very significant and this design style is no longer cost-effective.
Much more complicated functions are availabled as mass-produced integrated circuits, ranging from flip-flops to microprocessors. With increasing complexity comes flexibility – a microprocessor can be programmed to perform a near-infinite variety of tasks. Digital system design therefore consists, in part, of tasking standard components and connecting them together. Inevitably, however, some aspect of the functionality will not be available as a standard device. The designer is then left with the choice of implementing this functionality from discrete gates or of designing a specialized integrated circuit to perform that task. While this latter task may appear daunting, it should be remembered that the cost of a system will depend to a great extent not on the cost of the individual components but on the cost of connecting those components together.
New Words and Expressions
Notes
1. Next came the idea of depositing these circuits by evaporating the metal at high temperature in a vacuum.
译文：另一种方法是通过将金属在高温真空中蒸发沉积，形成电路。
此句是倒装句，主语是the idea，后面是它的修饰语，谓语为came。
2. It soon became obvious that relatively complicated circuits could be built up by using a series of masks on the substrate, each designed to permit deposition of one part of the circuit.
译文：很快，人们就可以采用一系列的基片掩模来制作相对复杂的电路了，每个单元掩模形成一部分电路。
“each designed…the circuit”是独立分词短语，做状语。
3. With these new methods of making electronic circuits we can be sure that the electronic device of the future, or radios, television sets, telephones, and so on, will become quite small.
译文：毫无疑问，在电路设计中采用的新的设计方法，将在未来大大缩小电子设备(诸如，收音机，电视机，电话机等等)的尺寸
“that the electronic devices…”是can be sure的宾语从句。
4. Synthesis and simulation EDA tools require that the design be transferred from the designer's imagination into the tools themselves.
译文：EDA的综合仿真工具可以将设计者的设计思想转化为具体实现。
5. Much more complicated functions are available as mass-produce integrated circuits, ranging from flip-flops to microprocessors.
译文：从简单的触发器，到复杂的微处理器，批量生产的集成电路可以实现更多、更复杂的功能。
Exercises
Ⅰ. Translating these paragraphs into Chinese
1. The data modulator produces a continuous-time waveform suitable for transmission through the channel, while the data demodulator's function is to extract the data from the received signal, now possibly distorted and noisy.
2. If you are new to electronics and would like to try adapting published projects, or designing and building your own circuits, you need to have a small stock of components available. However, there is a very wide range of components and it can be difficult to know which ones you really need! I hope the list below will help you choose a sensible selection which is within your budget. Remember that circuits built on breadboard can be dismantled after use and the components re-used.
Ⅱ. Reply the following questions according to the text
1. What did the development of the transistor bring about?
2. What advantages has the printed circuit?
3. What do we say that the integrated circuit is the most advanced of all the new methods of making electronic circuit?