基于单片机数字电压表电路设计外文文献原稿和译文

1、北京化工大学北方学院毕业设计（论文）一一外文文献原稿和译文 外文文献原稿和译文 原 稿 Front side Copyright of this circuit belongs to smart kit electronics. In this page we will use this circuit to discuss for improvements and we will introduce some changes based on origi nal schematic General Description This is an easy to build, but never

2、theless very accurate and useful digital voltmeter. It has been designed as a panel meter and can be used in DC power supplies or any where else it is n ecessary to have an accurate in dicati on of the voltage prese nt. The circuit employs the ADC (An alogue to Digital Co nverter) I.C. CL7107 made b

3、y INTERSIL. This IC in corporates in a 40 pin case all the circuitry n ecessary to convert an an alogue sig nal to digital and can drive a series of four seve n segme nt LED displays directly. The circuits built in to the IC are an an alogue to digital converter, a comparator, a clock, a decoder and

4、 a seven segment LED display driver. The circuit as it is described here can display any DC voltage in the range of 0-1999 Volts. Technical Specifications - Characteristics Supply Voltage:+/- 5 V (Symmetrical) Power requireme nts:.200 mA (maximum) Measuri ng ran ge:+/- 0-1,999 VDC in four ran ges Ac

5、curacy:0.1 % FEATURES Small size Easy con structi on Low cost. Simple adjustme nt. Easy to read from a dista nee. Few exter nal comp onen ts. How it Works In order to understand the principle of operation of the circuit it is necessary to explain how the ADC IC works. This IC has the following very

6、important features: Great accuracy. It is not affected by no ise. No n eed for a sample and hold circuit. It has a built-i n clock. It has no n eed for high accuracy exter nal comp onen ts. 1CL71D7 41 R3 T1H -tT T卜 Rr T T 1 Schematic (fixed 16-11-09) 10 9 8 7 6 PIN IE NO. 1 Cathode E 2 Cathode D 3 C

7、om. Anode 4 Cattiode C 5 Cathode DP 6 Cathode B 7 Cathode A 8 Com, Anode 9 Cathode F 10 Cathode G 7-segment display pinout MAN6960 An Analogue to Digital Converter, (ADC from now on) is better known as a dual slope con verter or in tegrat ing con verter. This type of con verter is gen erally preferr

8、ed over other types as it offers accuracy, simplicity in design and a relative indifferenee to noise which makes it very reliable. The operation of the circuit is better understood if it is described in two stages. During the first stage and for a give n period the in put voltage is in tegrated, and

9、 in the output of the in tegrator at t he end of this period, there is a voltage which is directly proporti onal to the in put voltage. At the end of the preset period the integrator is fed with an internal reference voltage and the output of the circuit is gradually reduced until it reaches the lev

10、el of the zero refere nce voltage. This sec ond phase is known as the n egative slope period and its duration depends on the output of the integrator in the first period. As the duration of the first operation is fixed and the length of the second is variable it is possible to compare the two and th

11、is way the in put voltage is in fact compared to the internal reference voltage and the result is coded and is send to the display. All this sounds quite easy but it is in fact a series of very complex operations which are all made by the ADC IC with the help of a few external components which are u

12、sed to con figure the circuit for the job. In detail the circuit works as follows. The voltage to be measured is applied across points 1 and 2 of the circuit and through the circuit R3, R4 and C4 is fin ally applied to pins 30 and 31 of the IC. These are the in put of the IC as you can see from its

13、diagram. (IN HIGH & IN LOW respectively). The resistor R1 together with C1 are used to set the frequency of the internal oscillator (clock) which is set at about 48 Hz. At this clock rate there are about three differe nt read ings per sec ond. The capacitor C2 which is conn ected betwee n pins 33 an

14、d 34 of the IC has bee n selected to compe nsate for the error caused by the internal referenee voltage and also keeps the display steady. The capacitor C3 and the resistor R5 are together the circuit that does the in tegrati on of the in put voltage and at the same time preve nt any divisi on of th

15、e in put voltage making the circuit faster and more reliable as the possibility of error is greatly reduced. The capacitor C5 forces the in strume nt to display zero whe n there is no voltage at its in put. The resistor R2 together with P1 are used to adjust the instrument during set -up so that it

16、displays zero whe n the in put is zero. The resistor R6 con trols the curre nt that is allowed to flow through the displays so that there is sufficient brightness with out damagi ng them. The IC as we have already men ti oned above is capable to drive four com mon anode LED displays. The three right

17、most displays are conn ected so that they can display all the numbers from 0 to 9 while the first from the left can only display the number 1 and when the voltage is negative the ?-? sign. The whole circuit operates from a symmetrica l p 5 VDC supply which is applied at pins 1 (+5 V), 21 (0 V) and 2

18、6 (-5 V) of the IC. Construction First of all let us consider a few basics in building electronic circuits on a printed circuit board. The board is made of a thin insulating material clad with a thin layer of conductive copper that is shaped in such a way as to form the necessary con ductors betwee

19、n the various comp onents of the circuit. The use of a properly desig ned prin ted circuit board is very desirable as it speeds con struct ion up considerably and reduces the possibility of making errors. To protect the board during storage from oxidation and assure it gets to you in perfect conditi

20、on the copper is tinned during manufacturing and covered with a special varnish that protects it from getting oxidised and also makes soldering easier. Soldering the components to the board is the only way to build your circuit and from the way you do it depends greatly your success or failure. This

21、 work is not very difficult and if you stick to a few rules you should have no problems. The soldering iron that you use must be light and its power should not exceed the 25 Watts. The tip should be fine and must be kept clean at all times. For this purpose come very handy specially made sponges tha

22、t are kept wet and from time to time you can wipe the hot tip on them to remove all the residues that tend to accumulate on it. DO NOT file or sandpaper a dirty or worn out tip. If the tip cannot be cleaned, replace it. There are many different types of solder in the market and you should choose a g

23、ood quality one that contains the necessary flux in its core, to assure a perfect joint every time. DO NOT use soldering flux apart from that which is already included in your solder. Too much flux can cause many problems and is one of the main causes of circuit malf un cti on. If n evertheless you

24、have to use extra flux, as it is the case whe n you have to tin copper wires, clean it very thoroughly after you finish your work. In order to solder a comp onent correctly you should do the follow ing: Clea n the comp onen t leads with a small piece of emery paper. Bend them at the correct distanee

25、 from the component由ody and insert the comp onent in its place on the board. You may find sometimes a component with heavier gauge leads than usual, that are too thick to enter in the holes of the p.c. board. In this case use a mini drill to enl arge the holes slightly. Do not make the holes too lar

26、ge as this is going to make solderi ng difficult afterwards. Take the hot iron and place its tip on the component lead while holding the end of the solder wire at the point where the lead emerges from the board. The iron tip must touch the lead slightly above the p.c. board. When the solder starts t

27、o melt and flow wait till it covers evenly the area around the hole and the flux boils and gets out from underneath the solder. The whole operati on should not take more tha n 5 sec on ds. Remove the iron and allow the solder to cool naturally without blowing on it or moving the component. If everyt

28、hing was done properly the surface of the joint must have a bright metallic finish and its edges should be smoothly en ded on the comp onent lead and the board track. If the solder looks dull, cracked, or has the shape of a blob then you have made a dry joint and you should remove the solder (with a

29、 pump, or a solder wick) and redo it. Take care not to overheat the tracks as it is very easy to lift them from the board and break them. When you are soldering a sensitive component it is good practice to hold the lead from the comp onent side of the board with a pair of long-nose pliers to divert

30、any heat that could possibly damage the comp onent. Make sure that you do not use more solder than it is necessary as you are running the risk of short-circuit ing adjace nt tracks on the board, especially if they are very close together. Whe n you finish your work, cut off the excess of the comp on

31、en t leads and clea n the board thoroughly with a suitable solve nt to remove all flux residues that may still remai n on it. 0 - 2 VR3 = 0 ohm 1% 0 - 20 VR3 = 1.2 Kohm 1% 0 - 200 VR3 = 12 Kohm 1% 0 - 2000 VR3 = 120 Kohm 1% When you have finished all the soldering on the board and you are sure that

32、everything is OK you can insert the IC in its place. The IC is CMOS and is very sensitive to static electricity. It comes wrapped in aluminium foil to protect it from static discharges and it should be handled with great care to avoid damaging it. Try to avoid touching its pins with your hands and k

33、eep the circuit and your body at ground potential when you insert it in its place. Connect the circuit to a suitable power supplyp 5 VDC and turn the supply on. The displays should light immediately and should form a nu mber. Short circuit the in put (0 V) and adjust the trimmer P1 un til the displa

34、y in dicates exactly ?0?. If it does not work Check your work for possible dry join ts, bridges across adjace nt tracks or solderi ng flux residues that usually cause problems. Check again all the external connections to and from the circuit to see if there is a mistake there. See that there are no

35、components missing or inserted in the wrong places. Make sure that all the polarised components have been soldered the right way round. Make sure the supply has the correct voltage and is connected the right way round to your circuit. - Check your project for faulty or damaged comp onen ts. Sample P

36、ower supply 1 Sample Power Supply 2 5V power supply 9 引言 这是一个很容易建立并且非常准确和有用的数字电压表。它被设计成一个面 板仪表，可用于直流电源供应器或其他需要有一个准确电压指示的地方。该电路 采用的ADC （模拟数字转换器）集成电路CL7107由Intersil公司生产。该IC采 用40引脚的情况下整合了所有必要的电路模拟信号转换为数字，可以直接驱动 4个7段LED显示。在IC中内置的电路是数字转换器，比较器，一个时钟，一 个解码器和一个 7段LED显示驱动器模拟。在这里它描述了一个可以显示在 0-1999电压范围的直流电压电路。

37、LED显示屏数字电压表技术规格-特征 电源电压： + / - 5V （对称）。 电源要求： 200mA （最大）。 测量范围： + / - 0-1,999V 在四个范围。 精度： 0.1 %。 特征： 小尺寸。 简易建筑。 成本低。 简单的调整。 易于读取距离。 很少的外部元件。 数字电压表的基本原则 为了了解电路的运作的原则，说明ADC的集成电路工程是必要的。该集成 电路具有以下非常重要的特点: 准确性。 抗干扰性。 无需要一个采样保持电路。 它有一个内置的时钟。 它不需要精度高的外部元件。 一个模拟数字转换器（ADC），从现在起更好的称为双斜率转换器或集成转换 器。这种类型的转换器通常优于

38、其他类型，因为它提供了准确，简洁的设计和它 可以将相对不重要的噪音变得非常可靠。如果将电路分两个阶段描述，该电路的 操作将更好的理解。在第一阶段的输入集成电压和最后阶段的输出集成电压中有 一个电压与输入电压成正比。在预设的时间结束时， 积分将到达内部基准电压以 及输出电路会逐渐降低直至达到零参考电压水平。第二个阶段就是所谓的负斜率 时期，其持续时间由第一阶段积分器输出而定。作为第一个操作时间是固定的， 第二个变量的长度就可以比较两个这样的输入电压，其实是相对于内部参考电 压，其结果是编码，然后发送到显示。 3 3 3 7 B 24 5 f te 24 n m it is ie i 10 m I

39、CL7107 示意图（固定 16-11-09） 北京化工大学北方学院毕业设计（论文）一一外文文献原稿和译文 13 10 9 8 7 6 IE NO. 1 Cathode E 2 Cathode D 3 Com. Anode 4 Cattiode C 5 Cathode DP 6 Cathode B 7 Cathode A 8 Com, Anode 9 Cathode F 10 Cathode G 7段显示器引出线 MAN6960 这一切听起来很容易，但实际上它是一系列非常复杂的操作，这些都是由 ADC集成电路作出了很少的外部元件，帮助它们用来配置工作的电路。详细的 电路的工作原理如下。为了进行

40、测量，需要将电压施加于电路的1和2点，最后 通过电路的 R3，R4和C4应用到集成电路的引脚30和31。从下图你可知这是 该集成电路的输入(分别为高与低)。R1电阻的C1 一起用来设置内部振荡器 (时 钟)，该设置约48Hz。在这个时钟速率大约有三个不同的每秒读数。连接集成电 路引脚33和34之间的电容已被选定，以弥补由内部参考电压带来的误差，并保 持稳定的显示。电容C3和电阻R5在一起的电路是输入电压的集成电路，同时 它可避免任何使电路更快的分裂输入电压，从而使错误的可能性大大减少进而使 电路更稳定。在没有输入电压时电容器C5强迫仪器显示为零。当输入为零时电 阻R2和P1 一起用来调整仪器在

41、设置过程中显示为零。电阻R6的控制电流允许 流经显示，以便使电路在没有损坏的前提下显示充分的亮度。至于我们上面已经 提到的芯片它能够驱动4个共阳极LED显示屏。这三个最右边的显示器相连， 使他们可以显示所有从 0到9的数字，而从左边第一个只能显示数字1，当电压 为负“-”的时候。整个电路工作，从对称p5伏直流电电源，这在引脚1(+5V) 申请，21(0V)，26(-5V)集成电路。 数字电压表印刷电路板的加工 首先让我们考虑建立一个印刷电路板上的电子电路的基础知识。该印刷电路 板是由薄绝缘铜的导电复合材料薄层形成，这样以形成电路之间的各组成部分的 必要的导体。一个设计完善的印刷电路板是非常可取的，因为它大大加快了加工， 并大大减少了决策失误的可能性。为了保护印刷电路板在存储过程中被氧化和保 证它到达你所要求的完美的条件，在生产过程中将铜镀锡的同时起表面还要覆盖 一层特殊的漆，这样不仅防止了它被氧化，也使焊接更容易。 焊接的部件，印刷电路板是建立你的电路的唯一的方式和你在做