For the troubleshooting of the Mitsubishi plc system, the six rules are followed, one touch, two look, three smells, four listens, five traces, and six replacements.
Touch, feel the temperature of the host CPU by hand, the normal operating temperature of the CPU does not exceed 60 ° C, the temperature acceptable for the hand is 36 ~ 38 ° C, the hand is not hot, normal; second look, look at the display lights on the main unit Whether the indicators of each module are normal; three smells, smells no smell, electronic components or cables are burned; four listen, listen to no change, loose nails, relays work normally, listen to the situation of the field staff Five failures are based on drawings and process flow to troubleshoot; six pairs of uncertain parts are replaced by parts to determine the fault.
Mitsubishi plc troubleshooting tips:
1. When the PLC is not operating normally, first check whether the RUN status of the CPU is normal. If it is not normal, it is basically due to a control program error. You can clear the CPU program and download the control program again.
When the PLC hardware is not normal, check the following order:
2. Power detection: Firstly, the power supply is detected. After normal, the PLC input and output terminals are detected, and the corresponding modules are replaced according to the detection results.
3. Understand the CPU working mode and priority: high priority has STOP, HOLDUP, STARTUP (WARMRESTART, COLDRESTART); low priority: RUN, RUN-P (PG/PC online reading and writing program). Check whether the CPU is in the RUN mode, or in the STOP mode, or the RUN mode flashing state and the STOP mode are both in the hold mode or the debug mode. If it is only in RUN mode, the CPU and each board are normally performing step 3. If the hold mode occurs, it may be that the user program has a breakpoint during the running process and is in the debugger state, or the breakpoint appears in the startup mode. In this case, re-commission the program and download the control program to the CPU again.
If it is STOP mode, visually analyze the cause of STOP:
A, no electricity, analysis of the reason for no electricity, is because the power supply department has a problem, or abnormal power failure (because there is a 1K3AH UPS to ensure that there is very little abnormal situation), usually under the circumstances of the repair and power, after the end of maintenance Manual power transmission. Then use the online function of Mitsubishi PLC to convert the working mode of the CPU from STOP to RUN;
B, the CPU is bad, replace the new good CPU of the same type and the same version;
C, the board is broken, and the board is replaced in an orderly manner. For hardware replacement, please pay attention to using the same product and the same version as the original device. Otherwise, the actual PLC configuration and the hardware configuration in the hardware configuration database of the corresponding programming software are different, and the normal cycle of the user control program cannot be performed. carried out.
4. Check the connection cable interface of Mitsubishi PLC to check if there is any looseness and see if the display lights are normal. If the fault light is found to be on, there is a bad module. When you check any point of the module, as long as there is no wiring and the address is not detected when the control program does not give an output signal, if it is connected, the point is abnormal, the normal is not normal; Perform another point of reconnection of the hardware connection line; in addition, we can also use the new module to replace the point of the module to be measured and turned on. If the point is broken, it is not good. For the point of the digital input module, when the coil is turned on, it is normally closed. It can be detected online or offline. If the meter detects that it is a bad point, it will be unreachable. Pass status. As long as the hardware wiring is re-switched and reconnected, the corresponding software should be used to replace the control software with 0X or 1X address. For the analog input module is the same as the digital input module, each channel is equivalent to a wire form, which is equivalent to the normally closed point, so the method of detecting the channel is good or bad. It is good when the state is on, and is bad when the state is off; the detection method of the analog output module is the same as that of the digital output module. If the bad channel is connected to the hardware, it is necessary to replace the channel and replace the corresponding 3X or 4X address in the control program. In addition, for the analog module, the selection of the range block should be checked, and whether the fuse is disconnected or not. Whether the software configuration is normal, (source: http://) is generally 1 to 5V voltage or 4 to 20mA current, which is selected according to the type of sensor and smart converter used. After the hardware point or channel replacement work is allowed, the CPU of the PLC must be STOP, and the program should be re-downloaded. If the condition is not allowed, the program will be downloaded directly with the update change without stopping the CPU. A good channel/good point for unused input modules is connected in series with the last used good channel/good point or special settings in the software.
5. The power module on the board of a large number of output modules cannot be powered off during normal production. Because the power is turned off at this time, the normally open relay in the relay cabinet will become normally open, which is prone to errors. To detect such an output module, it is necessary to contact the on-site operator to perform manual operation on the relevant equipment of this part, and then remove the power supply line of the digital output module and work on the module.
6, the detection of various types of switches: such as relays, proximity switches, air switches and other devices, the detection is based on whether the type of switch is normally closed or normally open, using the table to detect the state of its pass and nowhere The state is opposite to the good device state, then the device is broken and replaced. For the majority of the circuit, the normally open type is used, which is used to manually control or automatically control the on and off of the current; for the normally closed type, it is mainly used in the protection circuit. By this, it is possible to know how the normal state of the switch and protection devices normally recognizes the device.
7. The communication module is detected by using a simple new communication module to identify whether the module being used on the board is normal.
8. Measuring method of the wire: The wire is also carried out by detecting the on-off method. It is possible to use a known wire to detect a wire that is not known to be good or bad, by connecting a good wire to an unknown wire and measuring the on-off state.
9. Resistance detection: When detecting voltage in the charged state, the corresponding resistance is detected when there is no charging.
By detecting, most of the faults in the work can be eliminated. In addition, since this work involves the intersection of AC single-phase electric 220V and DC 24V, pay attention to accumulating safe electricity knowledge and common sense, and safety precautions during work. And gas safety procedures to ensure safe operation.
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