Application of the hottest ddm4a product in large

Introduction to the application of ddm4a products in large and medium-sized analog display screens

a medium-sized water plant plans to be equipped with a set of large screen analog display screens for the central control room. The analog quantity to be displayed includes the working parameters of each power distribution equipment and circuit (three-phase voltage, current, power, accumulated electricity, which is the key link for the promotion and utilization of new materials), the working current of each water pump, water level, raw water flow, clean water tank level, water supply pump working current, water supply pressure and flow, dosing, chlorination amount, residual chlorine quality, pH value and other related parameters, about 32 parameters

in the past, PLC Analog output module was generally used to drive ordinary analog display tables. In this way, dozens of analog channels and dozens of ordinary digital meters are required. We know that each channel of PLC analog quantity needs about 700 ~ 900 yuan, plus nearly a thousand yuan of ordinary analog quantity digital display meter

moreover, because there are too many engineering quantity parameters, it is very troublesome for PLC to convert each parameter into a physical quantity suitable for voltage display, and then set the range on the ordinary analog display table or adjust the proportion through resistance to meet the display. And it needs to be measured regularly. After replacing the ordinary analog quantity display meter, it must be adjusted to the appropriate engineering quantity display range. The common analog display table is 0 ~ 200mV, corresponding to the display range of 0 ~ 1999

for example, the PLC Analog output module is used to drive the ordinary analog display table to display the residual chlorine value, which generally ranges from 0.05 to 0.30ppm

we cannot directly display the value of this range on the ordinary analog digital display meter, but we must convert it to a voltage value of 0.05 ~ 0.30v. The corresponding PLC output voltage range is 5 ~ 30mV, and then the second digit of the decimal point is set to light up. Due to the certain conversion error of PLC Analog output itself, plus the error of analog meter itself, and the small signal is easily disturbed, the last digit itself is inaccurate, so the error is large and the reliability is poor

for another example, if the display speed is 3000 rpm, you must select a 4-bit and a half ordinary analog quantity display meter. First, calculate that the corresponding speed range of the analog quantity output is 0 ~ 2V, and then attenuate to 0 ~ 300mV through the resistance network. In this way, the 0 ~ 1999mv voltage signal can be converted into 0 ~ 3000rpm display. The attenuation ratio is 2000/300. Debugging and use are quite troublesome, and the error is also large

if ddm4a series digital display meter is used, there is no such problem

if we choose several Japanese Mitsubishi FX2N series PLCs as the main control equipment of the project, see the network control structure diagram in the figure below

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and one of the plc5s is used as the control equipment of the analog display screen, see the schematic diagram of the analog display screen in the figure below

we have scheduled the PLC display buffer data area to be D100 and the decimal point display buffer data area to be D101. D100 is composed of d0, D1, D2 and D3, which represents the display data of ten, hundreds and thousands. See the communication format below. The DDM series digital display subroutine in PLC can be called regularly, or the display subroutine can be called after the display data changes

l display the pressure value of the main pipe: FX2N － 4AD module collects the current pressure of 0.346mpa, converts the collected current pressure data to 34, d3d2d1d0 is stored as D3 = 0, D2 = 3, D1 = 4, d0 = 6, and D100 = 0346 combined into PLC. Because the decimal point display format is 0.000, therefore, D101 should be set to 4. The display table will automatically display 0.346. If special symbols need to be displayed,

can be handled in the following way:

d3d2d1d0 is stored as D3 = 11, D2 = 0, D1 = 3, d0 = 4 respectively, and D100 = b346 (BCD code) merged into PLC. Since the decimal point display format is 0.00, D101 should be set to 3. The display table will automatically display as p0.34

2 display the speed value of the water supply pump: FX2N Google used to search every 28 days for a period of time) 4AD obtained the speed value of the water pump motor as 1040rpm. Store this value directly in D3 = 1, D2 = 0, D1 = 4, d0 = 0. Since there is no need to display decimal points, D101 = 0. The display table will automatically display 1040

3 shows the water level value of the clean water tank: fx2n-4ad obtains the water level value of a clean water tank of 4.03M. Store this value directly in D3 = 0, D2 = 4, D1 = 0, d0 = 3. Since the decimal point display format is 0.00, D101 should be set to 3. The display table will automatically display as 4.03

4 display residual chlorine value: plc-4ad obtains the output value (4 ~ 20mA) of residual chlorine analyzer corresponding to 0 ~ 0.30ppm, and then detects the corresponding data value, for example, 12mA, that is (12/16) × 0.3=0.225。 Store D100 = 225, that is, d3d2d1d0 as D3 = 0, D2 = 2,

d1 = 2, d0 = 5, and D101 as 4, so the display table directly displays 0.225

5 display year, month, day and time: for example, to display 2002, PLC clock data can be directly stored in D100, corresponding to D3 = 2, D2 = 0, D1 = 0, d0 = 2. Since there is no need to display decimal points, D101 = 0. The display table will automatically display as 2002

in a word, the engineering quantity display system composed of DDM series display table + PLC is very convenient and flexible. It can truly display the data, which is exactly the same as the data you calculated. There is no need for expensive analog module, which greatly saves the cost of the display system by avoiding the splashing of the broken sample

6 hardware design of PLC and ddm4a: according to the display needs, a total of 32 data need to be displayed on the analog display screen, and the configuration is as follows:

a. configure a total of 32 ddm4a digital display tables

b. due to the need to select the PLC transistor output drive module. Because the price of FX0N is lower than that of FX2N module and it is fully compatible, on the one hand, we can use fx0n-8eyt module with 8 output points on each module to further reduce the cost

one ddm4a meter can be driven according to every four output points. According to the refresh speed requirements of the display table, every four output points can be arranged as a group of serial BCD code drive lines, with eight ddm4a display meters in each group. Each meter is equipped with a PLC output point as the strobe end of the instrument, so the code display table can be directly driven. In the future, one group (four output points) can drive eight tables for each additional eight blocks. In this way, we can configure four groups of serial BCD code

drive lines, which can drive eight tables in total × 4 = 32 digital display meters. Therefore, three fx0n-8eyt modules can be selected, totaling 24