How to use power-down holding registers when repairing PLC - Database & Sql Blog Articles

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Photocoupler

In the plc repair work, electrical engineers found that when designing a small PLC control system, in order to meet the needs of the production process, it is often necessary to change the internal data of the PLC outside the PLC, such as the value of Counter, Timer or Data. At the same time, these data are required to be saved in the PLC after the system is shut down. In this case, the data can be transferred and used after the next power-on.
In the PLC maintenance work, we have a way to solve this problem, hoping to provide some valuable reference for everyone.
Many small PLCs now provide power-down holding registers to varying degrees to save the data that the user wants to save when the PLC is powered off. But most of the time, in order to save costs, PLC manufacturers do not provide a sufficient number of power-down holding registers for system designers to use, so when the adjusted data items exceed the number of power-down holding registers in the PLC, we can only Reduce the adjusted data items (fixed or not) or purchase a PLC with more power-down holding registers. In this way, product grades are reduced or costs are increased, making the production machinery inflexible and adaptable to board maintenance.
Example:
Panasonic FP0-C16T PLC, the adjusted data is 16, the PLC internal power-down holding register number is 10, including 8 data registers (8 DT1652-DT1659, 16Bit) and 2 words of internal relays (WR61, WR62, 16Bit). If the conventional one of the adjusted data occupies a data register, it is obviously impossible to adjust the 16 adjusted data, and only 10 adjusted data can be adjusted. Therefore, we analyzed the data adjustment range of 16 adjusted data, and found that the adjustment range of these data only needs to be from 0 to 255, that is, 0 to 28-1; and the internal data size of the power-down data register DT1652 is 216. -1, which is 256 × 256-1; so we can use only one adjusted data to the lower 8 bits of the data register. The DR can then store the other adjusted data by the upper 8 bits of the data register.
List the PLC repair procedures for this section:

1. After booting up, merge the data of the other two data registers into the upper 8 bits and lower 8 bits of the power-down holding register:
R9014 is a pulse relay that is specified in the Panasonic FP0 series PLC and starts to operate in the second PLC scan cycle when the PLC goes from the program state to the run state.
The instruction F66 is a word or instruction that causes the data in the general data register DT20 to be word-ORed with the data in the general data register DT0, and the result is sent to the power holding register DT1655. The instruction F121 is a left shift instruction without carry, and K8 is shifted left by 8 bits.

2. When powering on, separate the upper 8 bits and the lower 8 bits of the power-down holding register to the other two data registers:
Among them, R9013 is a pulse relay that is specified in the Panasonic FP0 series PLC and only operates one PLC scan cycle when the PLC goes from the program state to the run state.
The instruction F65 is a word and instruction. Its function is to make the word in the power-down hold data register DT1655 and the hexadecimal number FF, and then send the result to the general data register DT0, so that the power can be separated. The lower 8 bits of the data in the data register DT1655 are held; likewise, the words and instructions of the second row can be separated from the upper 8 bits of the data in the power-down data register DT1655.
The instruction F120 is a command that does not carry a right shift, that is, when the data word is shifted to the right, the high bit is zero-padded. K8 means shifting 8 bits to the right.
The instruction F0 is a word transfer instruction that transfers the data in the general data register DT10 to the general data register DT1.
The purpose of the above program segment is to divide the data in the power-down hold data register DT1655 into two adjusted data at power-on. Shanghai Sanguang Digital Technology Co., Ltd. has obvious advantages in the maintenance industry. In addition to its strong technical strength, it also cooperates with Hong Kong Hengfa Technology Co., Ltd. to completely solve integrated circuits, cold chips, current sensors, voltage sensors, and current transducers. , voltage transmitters, switching power supplies and supply of various common electronic components.

It can be seen from the PLC maintenance procedure above that the data in the general data registers DT0 and DT1 can be arbitrarily changed while the PLC is running, and these changes are also sent to the power-down holding register DT1655, so that when the PLC is powered down, The adjusted data is also saved.
In the usual PLC maintenance work, through the same method, we can flexibly use each bit of the power-down holding register according to the size of the adjusted data, so that we can repair the PLC without increasing the cost. Improve the performance of small PLC control systems.

In automatic control, clock and time control is often used. For example, automatic ringing and automatic control equipment for school classes are controlled by H period and time. Some PLCs have real-time clock function. This article intends to set and display the time of various PLCs, how to realize time control, and talk about the obvious insights.

1 clock calibration and time data call

1.1__PLC without clock function
____PLC's clock to establish the inorganic internal clock machine to obtain the clock control function, 1I to compile a clock program, if you want to choose the first year before programming. The storage unit of month, day, hour, minute and second, then use the internal time base as the standard timing pulse, for example, add the second working unit by 1 with the second pulse, return to zero when added to 60s, and enter the sub-working unit. Hit l hour 6O minutes, 1 day 24 hours, Taiyue 3l days, Xiaoyue porridge days, poisonous dance ç¾¹ most, February 1 plus 1 day, 1 year l2 months of regular design clock program. The timing and time data acquisition of this homemade clock is similar to the built-in clock in the machine, and the Toshiba CT repair is not repeated. Open to keep the red and green lights H{flash.

1.2__PLC with clock function and clock command
____ There are many PLCs with clock function and related instructions, such as Siemens' LOGO! Mitsubishi's a controller and other miniature models. After the power is turned on, the internal clock will automatically enter the running state, and it can be used in this The time value is displayed and set on the display that comes with the machine. Figure 1 is a program completed by LoGO! using the 阉 programming language. The marked box in the figure is called the time switch in the LOGO! command. It can set multiple sets of time at the same time. The setting of the time switch in this program turns ON from Monday to Friday at 09:00, and turns off at 18:30. ; turns to ON at 14:30 on Saturday, turns OFF at 22:30; turns ON at 7:30 on Sunday, becomes 2:30
OFF, which is an example of a switch for 3 different time period controls. In addition, LOOO! also has an annual clock command that can be used for monthly and target time control. In this type of PLC, the setting of the time period and the correction of the internal clock can be as convenient as adjusting the electronic watch by using the programming button that is equipped with the machine.
____ Siemens' $7-200 and s7-300 series PLCs also have clock functions. Unlike LOGO!, when using the clock function, you must first transfer the real-time time value to a certain data unit, and use the set clock command to specify these memory units as the year, month, day, hour, minute, second, and week of the clock. Dedicated unit. After this setting, the values ​​of these units change according to the law of time. When you need to use the time information, you also need to use the read time command to read the time value into a certain storage unit to use. X-ray machine maintenance Figure 2 is an example program for clock creation and reading of a PLC
The eight memory units VB210~VB217 in the ____ program have been sent with certain time data in advance. The timing of such a clock can be achieved by sending new time data to these memory locations. In the time control involving only hours, minutes and seconds, a calibration button can be used to connect a calibration button to the input port of the machine, and a program for transmitting the calibration time data is written in the software, and the button is used as a program. Execution conditions. It is required to set the calibration time at 8:00 am. When the standard time is 8:00, press the calibration button to complete the calibration function. To implement the random calibration function, a dedicated data input device, such as a programmer matrix switch, data unit or graphic unit, is required for maintenance.

1.3__accident audio signal
____ When QF is tripped by relay protection action. In order to attract the attention of the duty officer, a bee device was installed. In order to avoid the accidental sound device when starting manual jump, closing and automatic reclosing. In practice, the method of connecting two pairs of contacts in the control switch in series is used. That is to say, 1-3 and 19-17 are only connected to the power supply after the closing, and the principle of the same state is simultaneously turned on.

2 flash signal
____ The current live flash signal is provided by the flash relay. After switching to the PLC, the flash signal can be realized by simply using its internal two timers to form an oscillating circuit, thus eliminating the trouble of external wiring. The specific implementation such as the ladder I shown in Figure 3 I / 0 allocation as shown in Table 1

3 notice signal
____ The notice letter is to help the on-duty personnel to judge the faulty equipment and its nature, so as to take measures to deal with it in time to prevent the accident from further expanding. In order to save the contact point of the PLC, use the joint of the warning signal exit relay to drive the PLC to input the eight-end X(x). Output Y (Y.), Y. Drive or indirectly drive light plates and alarm bells. As shown in Figure 2
____ Because PLC performance is very good. Therefore, the accuracy and reliability of the central signal action are guaranteed. Although the price of PLC is higher than the ZC-23 type impact relay currently used in the field, it is easy to use, requires less maintenance work, and the secondary circuit is simple.
____ Although this experiment failed to lose A and output more accidents and warning signals, it verified the input letter, and the output was in full compliance with the site requirements. If it is put into use, simply extend the contact of the PLC through the expansion unit and the expansion module, or directly select the PLC with multiple I/0.