AB PLC common troubleshooting methods

In the long-term maintenance of Rockwell’s A-B‘s plc controller, some of the A-B PLC controllers are summarized, and some of the common faults are practical and effective in the actual production.
Rockwell A-B PLC’s hardware series are PLC5, ControlLogix, SLC500, MicroLogix, etc .; commonly used communication software RSLinx, etc .; monitoring interface software Intouch, RSView32, etc .; programming software RSLogix5, RSLogix500, RSLogix5000. Is for my factory used A-B PLC controller and common troubleshooting methods for some simple introduction.
Zhaotong cigarette factory used A-B PLC controller has two types, one is PLC5, the other is SLC500. Both the power modules are not accounted for slot, and the difference is PLC5 CPU module does not occupy the slot, SLC500 CPU is accounted for the slot, and the former volume of the latter is small. PLC5 programming software is RSLogix5, and SLC500 with the programming software is RSLogix500.
The programming software they used was developed in conjunction with Microsoft, whose features and features include:
1, a free format ladder editor, which allows users to write programs only focus on the logic of the program logic without attention to the grammar of the right or wrong;
2, with a validator, the user can use it to create a list of errors, which can be modified at a convenient time;
3, with drag-and-drop editing function, you can quickly move between subroutines or a cascade of steps between the steps between the fast move instructions;
4, a query and replace the function, can quickly change the value of a specific address or symbol;
5, the program’s user interface all the file directory can be click through the mouse to enter;
6, a data monitoring function, which can display independent data elements to observe the interaction between them;
7, there are bar graph function, you can use it to monitor data and so on.
RSLinx software is a copy of RSLogix software. When running CPU communication on RSLogix, you must run RSLinx Lite, which is the interface software for communication.
SLC500 module is generally 1746- × × ×, CPU is 1747, it is the location of the choice of slot, the power module is generally 1746-P1, P2, P3, P4, only P3 is 24 V DC, the rest are 220 volts AC input. PLC5 its CPU is 1785-L20, L30 … …, can connect up to four remote I / O channel, up to 32 remote I / O nodes (physical devices), the power module for the 1771-P7. PLC5 addressing mode has 2 slots addressing, 1 slot addressing, 1/2 slot addressing. 2-slot addressing is a physical 2-slot I / O group corresponding to one word (16 bits) in the input / output map table. 1 Slot Addressing A physical slot corresponds to a word (16 bits) in the input / output map table. 1/2 slot addressing is a physical slot corresponding to two words (32 bits) in the input / output map table.
Two types of CPUs have key switches that can be switched between RUN, PROG and REM, RUN is running, PROG is programmed, and REM is between software and can be defined as RUN or PROG. REM is RUN, if from PROG to REM is PROG. SLC500 its CPU lights are RUN, FLT, BATT, DH +, FORCE, RS232, respectively, when the lights are normal, fault, battery, DH + communication normal, forced output, serial communication. PLC5 its CPU on the lamp BATT lit when the battery voltage is insufficient; PROC green that run, red that failure; FORC lit when forced I / O is valid; COMM lit when the communication state is normal. The communication between them includes the remote adapter card DH + communication link, the host computer by running the computer RSLinx Lite or RSLinx Gatewey software for CPU communication. Local programming can be used RS-232 or DH + communication link, remote programming can be used DH + or Ethernet.
A-B PLC5 and SLC500 procedures are generally not easy to lose, so the failure of the general performance of communication failure and module failure. A-B PLC hardware performance is relatively stable, so dry ice line PLC failure is very common, generally have the following:
1, the analog input is displayed as a value, will not change, a situation for the boot before the emergence of such a situation first look at the analog input module is turned on red light, if it is turned off the power switch module check Whether the module is burned, if the bad replacement, if not bad or no light is the data transmission failure or scan failure, encountered this situation is generally re-power on the PLC can be restored. The other for the operation of the emergence of this situation is generally CPU module and analog module failure, and sometimes re-power can be restored, if not recover may be broken CPU module.
2, the operation command is not implemented, that is, the operation does not work, this situation generally there are two possibilities, one is the operation should have the conditions are not met, so the operation does not move. The other is for the program itself in a closed loop that is dead loop or scan time overflow caused by the output ban, or communication failure, in which case you can stop the system and then restart, or the system power and then hit the automatic And start that can be restored, if not restored to the PLC on the power of the general operation can also be restored.
3, all the output of the PLC are not, that is, all the output should have the corresponding point on the module lights are not bright. There is only one possibility that the 24-volt power supply provided by the output module is not available. In one case, the intermediate relay is not supplied with the power supply to the output module. The other condition is that the intermediate relay coil is burned or the contact Poor contact.
4, the signal can not be received delay, resulting in a control unit can not operate. This situation is a communication failure or data transmission failure, generally the signal generated by the steps to re-do it again to restore.
5, PLC all the input and output modules are not green light. Encountered this situation first look at the power module input is not 220V AC, not to check the power supply transformer is good or bad, if there is a power module is broken.
6, in the course of running, the online device suddenly does not move, that is, PLC suddenly “crash”, encounter this situation first look at the state of PLC, if all the lights on the module are not bright, then most likely PLC power The module is broken; if you press the CPU with the finger when all the lights on the module and bright, then the power to remove the CPU and then plug in the general case can be ruled out the fault. Another situation is that a few pieces of input and output module input and output points are not displayed, this case in the exclusion of input and output modules failure, plug the CPU can also generally rule out the fault.
7, the CPU on the DH + or COMM light flashes or red, that is, communication failure. A case for the DH + cable is broken or the socket is loose, check the handling of DH + cable and jack until the fault disappears; another case for the CPU communication address is wrong or be changed, then must enter the RSLinx, click the communication configuration icon reconfiguration With red fork of the host computer or PLC icon address, until the red cross disappeared.
In short, in the actual production process will encounter a variety of PLC failure, although the AB PLC hardware performance is relatively stable, the possibility of failure is very small, but for our electrical maintenance personnel, whether AB PLC or Siemens PLC, as long as we use it, we must master it. PLC programmable controller software and hardware knowledge we are always in a state of lag, only through continuous learning, so that they master some of the PLC maintenance methods and common troubleshooting methods in order to make PLC better for our services.