1、digital voltage meter Based on single-chip technologySingle chip is an integrated on a single chip a complete computer system. Even though most of his features in a small chip, but it has a need to complete the majority of computer components: CPU, memory, internal and external bus system, most will

2、 have the Core. At the same time, such as integrated communication interfaces, timers, real-time clock and other peripheral equipment. And now the most powerful single-chip microcomputer system can even voice, image, networking, input and output complex system integration on a single chip.Also known

3、 as single-chip microprocessor, first because it was used in the field of industrial control. Only by the single-chip CPU chip developed from the dedicated processor. The design concept is the first by a large number of peripherals and CPU in a single chip, the computer system so that smaller, more

4、easily integrated into the complex and demanding on the volume control devices. INTEL the Z80 is one of the first design in accordance with the idea of the processor, From then on, the MCU and the development of a dedicated processor parted ways.At present, single-chip to infiltrate all areas of our

5、 lives, which is very difficult to find the area of almost no traces of single-chip microcomputer. Missile navigation equipment, aircraft control on a variety of instruments, computer network communications and data transmission, industrial automation, real-time process control and data processing,

6、are widely used in a variety of smart IC card, limousine civilian security systems, video recorders, cameras, the control of automatic washing machines, as well as program-controlled toys, electronic pet, etc., which are inseparable from the single-chip microcomputer. Not to mention the field of rob

7、ot automation, intelligent instrumentation, medical equipment has been.Throughout the development process of single-chip, you can indicate the development trend of single-chip, generally are: 1. Of low-power CMOS MCS-51 series of 8031 introduced the power consumption of 630mW, and now widespread in

8、the single-chip 100mW or so, with the growing demand for low-power single-chip, and now all the basic single-chip manufacturers are use of CMOS (complementary metal oxide semiconductor process). As the 80C51 on the use of HMOS (high density metal oxide semiconductor process) and CHMOS (high-density

9、complementary metal oxide semiconductor process). Although the CMOS low power consumption, but because of its physical characteristics to determine its speed is not high enough, and then CHMOS with high-speed and low power consumption characteristics of these features, it is more suitable in low pow

10、er consumption, as battery-powered applications . Therefore, the process for some time to come will be the main way to develop single-chip microcomputer. 2.Singal-chip of micro-chip Now generally in conventional single-chip will be the central processing unit (CPU), random access data storage (RAM),

11、 read-only program memory (ROM), parallel and serial communication interface, system interruption, timing circuits, integrated circuit clock in a single chip, enhanced single-chip integration, such as A / D converter, PMW (pulse width modulation circuit), WDT (watchdog), and some will be single-chip

12、 LCD (LCD) driver integrated circuits are in a single chip, this unit includes single-chip circuits on more and more powerful features. Even single-chip manufacturers can also be tailored in accordance with the requirements of users, to create a single chip with its own chip characteristics.3. Mains

13、tream and multi-species coexistenceAlthough a wide variety of single-chip, unique, but still single-chip microcomputer 80C51 prevailing at the core, compatible with its structure and command system of PHILIPS products, ATMEL companys products and China Taiwans Winbond Series single-chip machine. The

14、refore, single-chip microcomputer as the core C8051 occupied the half. Microchips PIC and reduced instruction set (RISC) has a strong development momentum of China Taiwan HOLTEK single-chip companies in recent years, increasing production, with its high quality low-cost advantages, to occupy a certa

15、in market share. MOTOROLA addition to the companys products, several large companies in Japans exclusive single-chip microcomputer. A certain period of time, this situation will continue to be upheld, there will not be a single-chip monopoly domination, taking the complementary interdependence, comp

16、lementarity and common development.AT89C51 is a flicker with 4K bytes EEPROM-programmable low-voltage, high-performance digital microprocessors CMOS8, commonly known as single-chip microcomputer. AT89C2051 is a flicker with 2K bytes EEPROM programmable microcontroller. MCU EEPROM erasure can be repe

17、ated 100 times. The device ATMEL manufacture high-density nonvolatile memory technology with industry-standard MCS-51 instruction set and pin compatible output. Owing to the multi-purpose 8-bit CPU and flash memory chips in a single portfolio, ATMELs AT89C51 microcontroller is a highly efficient, AT

18、89C2051 is a streamlined version of it. AT89C single-chip embedded control system for many provides a flexible and inexpensive program.AT89C51 performance : 1. And MCS-51 compatible 2.4K bytes of programmable Flash Memory 3. Life expectancy: 1000 write / wipe cycle 4. Data retention time: 10 years 5

19、. Static work of the whole: 0Hz-24MHz 6. Three-level Program Memory Lock 7.128 8-bit internal RAM 8.32 Programmable I / O lines 9. Two 16-bit timer / counter 10.5 Interrupt Sources 11. Programmable Serial Channel 12. Low-power idle and power-down mode 13. Chip oscillator and clock circuitryReferred

20、to as digital voltage meter DVM, it is a digital measurement technology, the continuous analog (DC input voltage) into a non-continuous, discrete digital form and the instrument display.The characteristics of digital voltage meter：1. Show a clear intuitive, accurate readingsTraditional analogue inst

21、ruments through the use of indicators must be carried out and dial readings in the reading process will be introduced to the inevitable human error. Digital voltage meter is the use of advanced digital display technology, so that the measurement results at a glance, as long as the meter jump phenome

22、non does not occur, the measurement results is unique.2. Show that the median Show that the median is usually 31 / 2, 32 / 3, 33 / 4 / spaces, 41 / 2, 43 / 4, 51 / 2, 61 / 2, 71 / 2, 81 / 2 A total of 9. Determine the median number of instruments there are two principles:1. can display all the numbe

23、rs 0 to 9 are the integer-bit; Score-bit numerical value is based on the largest show the highest number of elements, with the highest number of full-scale as the denominator .3. High accuracy Accuracy of results is a measure of systematic error and random error of the integrated. 4. High resolution

24、 Digital voltage meter at the lowest voltage range on the bottom of a character represented by the voltage value, known as the instrument of the resolution, which reflects the level of instrument sensitivity. With the display resolution increases the median. Resolution refers to the smallest can be

25、shown in the figures (except zero) and the largest percentage of the number. For example, 31 / 2 DVM of a resolution of 1 / 1999 0.05%. Be noted that the resolution and accuracy are two different concepts. From the measurement point of view, the resolution is true indicators (with measurement error

26、has nothing to do), the accuracy is the real target (on behalf of the size of measurement error). 5. Wide measuring range DVM generally more measurable range 0 1000V DC voltage, high voltage probe can be measured with the million-volt high-pressure.A / D converter 4 is a digital voltage meter, digit

27、al multimeter and measuring system the heart. At present, domestic production of A / D converter has reached hundreds of species can be broadly divided into five main categories: 1. monolithic A / D converter; 2. DMM dedicated single-chip IC; 3. dedicated multi-display meter IC; 4. for digital the u

28、se of special instrumentation IC (ASIC); 5. other general-purpose A / D converter, the chip can only complete A / D converter, not directly with the number of instruments.Digital voltage meter digital meter is a great core and foundation of the digital voltage meter as a continuous analog DC voltage

29、 to a discrete form of non-sequential numbers, which is different from traditional dial indicator readings to increase the ways to avoid errors in reading and visual fatigue. At present, the digital multimeter is a core component of the internal A / D converter, converter, to a large extent affect t

30、he accuracy of the accuracy of the design of digital multimeter - Digital Voltage Meter A / D converter for converting analog signals ADC0804 input, AT89C51 controls the heart of the transformation and processing the results of operations, the final output device driver number of voltage signal. Dig

31、ital voltage meter digital meter is a great core and foundation of the digital voltage meter as a continuous analog DC voltage to a discrete form of non-sequential numbers, which is different from traditional dial indicator readings to increase the ways to avoid errors in reading and visual fatigue.

32、 At present, the digital multimeter is a core component of the internal A / D converter, converter, to a large extent affect the accuracy of the accuracy of the design of digital multimeter - Digital Voltage Meter A / D converter for converting analog signals ADC0804 input, AT89C51 controls the hear

33、t of the transformation and processing the results of operations, the final output device driver number of voltage signal. LED display can be carried out will be displayed after the decimal point voltage value of one.Adoption of new technologies, new processes, from LSI and VLSI constitute a new typ

34、e of digital instrumentation and a large number of high-end smart devices available, the field of electronic devices marked a revolution in creating a modern pioneer of electronic measurement technology.Front sideCopyright of this circuit belongs to smart kit electronics. In this page we will use th

35、is circuit to discuss for improvements and we will introduce some changes based on original schematicGeneral Description This is an easy to build, but nevertheless very accurate and useful digital voltmeter. It has been designed as a panel meter and can be used in DC power supplies or anywhere else

36、it is necessary to have an accurate indication of the voltage present. The circuit employs the ADC (Analogue to Digital Converter) I.C. CL7107 made by INTERSIL. This IC incorporates in a 40 pin case all the circuitry necessary to convert an analogue signal to digital and can drive a series of four s

37、even segment LED displays directly. The circuits built into the IC are an analogue to digital converter, a comparator, a clock, a decoder and 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 - Ch

38、aracteristicsSupply Voltage: . +/- 5 V (Symmetrical)Power requirements: . 200 mA (maximum)Measuring range: . +/- 0-1,999 VDC in four rangesAccuracy: . 0.1 %FEATURESSmall size Easy construction Low cost.Simple adjustment.Easy to read from a distance.Few external components.How it Works In order to un

39、derstand the principle of operation of the circuit it is necessary to explain how the ADC IC works. This IC has the following very important features:Great accuracy.It is not affected by noise.No need for a sample and hold circuit.It has a built-in clock.It has no need for high accuracy external com

40、ponents.Schematic (fixed 16-11-09)7-segment display pinout MAN6960An Analogue to Digital Converter, (ADC from now on) is better known as a dual slope converter or integrating converter. This type of converter is generally preferred over other types as it offers accuracy, simplicity in design and a r

41、elative indifference 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 given period the input voltage is integrated, and in the output of the integrator at the end of this period, there is a vol

42、tage which is directly proportional to the input 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 level of the zero reference voltage. This second phase is known as the negative s

43、lope 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 this way the input voltage is in fact compared to the internal reference voltage an

44、d 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 used to configure the circuit for the job. In detail the circuit works as follows. T

45、he voltage to be measured is applied across points 1 and 2 of the circuit and through the circuit R3, R4 and C4 is finally applied to pins 30 and 31 of the IC. These are the input of the IC as you can see from its diagram. (IN HIGH & IN LOW respectively). The resistor R1 together with C1 are used to

46、 set the frequency of the internal oscillator (clock) which is set at about 48 Hz. At this clock rate there are about three different readings per second. The capacitor C2 which is connected between pins 33 and 34 of the IC has been selected to compensate for the error caused by the internal referen

47、ce voltage and also keeps the display steady. The capacitor C3 and the resistor R5 are together the circuit that does the integration of the input voltage and at the same time prevent any division of the input voltage making the circuit faster and more reliable as the possibility of error is greatly

48、 reduced. The capacitor C5 forces the instrument to display zero when there is no voltage at its input. The resistor R2 together with P1 are used to adjust the instrument during set-up so that it displays zero when the input is zero. The resistor R6 controls the current that is allowed to flow throu

49、gh the displays so that there is sufficient brightness with out damaging them. The IC as we have already mentioned above is capable to drive four common anode LED displays. The three rightmost displays are connected so that they can display all the numbers from 0 to 9 while the first from the left c

50、an only display the number 1 and when the voltage is negative the - sign. The whole circuit operates from a symmetrical 5 VDC supply which is applied at pins 1 (+5 V), 21 (0 V) and 26 (-5 V) of the IC.Construction First of all let us consider a few basics in building electronic circuits on a printed

51、 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 conductors between the various components of the circuit. The use of a properly designed printed circuit board is very desirable as it spe

52、eds construction 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 condition the copper is tinned during manufacturing and covered with a special varnish that protects it from getting oxidised and als

53、o 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 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 b

54、e 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 that 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.

55、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 good quality one that contains the necessary flux in its core, to assure a perfect joint every time. DO NOT use soldering flux ap

56、art 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 malfunction. If nevertheless you have to use extra flux, as it is the case when you have to tin copper wires, clean it very thoroughly after you finish your work.In

57、order to solder a component correctly you should do the following:Clean the component leads with a small piece of emery paper.Bend them at the correct distance from the components body and insert the component in its place on the board.You may find sometimes a component with heavier gauge leads than

58、 usual, that are too thick to enter in the holes of the p.c. board. In this case use a mini drill to enlarge the holes slightly. Do not make the holes too large as this is going to make soldering difficult afterwards.Take the hot iron and place its tip on the component lead while holding the end of

59、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 to 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 operation should no