Because Siemens PLC programmable control system is widely used in industrial manufacturing, many engineering engineers pay more and more attention to the specific methods of PLC control circuit problem judgment and maintenance technology. Today we will give a brief introduction to the judgment of PLC control circuit and the specific methods of maintenance technology, hoping to have a certain role for those who need it.
1. Siemens PLC input and output
A small Siemens PLC can sensitively operate a complex electrical control cabinet mechanical equipment. What we can see is the upper and lower relay terminals with staggered output, the corresponding indicator lights and the number of Siemens PLC, as if there are more than ten feet. electronic components. If someone does not see the schematic to repair the problem with the machine, it is very likely that they do not know how to start, or even find the problem is very slow.
Specifically for this kind of thing, we can make a table according to the electrical schematic diagram, paste it on the console or control cabinet, and mark the Siemens PLC output terminal number and its corresponding electrical symbol, Chinese name, that is, similar to the function of electronic component pins illustrate. With this output table, electricians who have a certain understanding of the operation process of mechanical equipment or are familiar with ladder diagrams can start maintenance.
2. Input circuit maintenance
To judge the quality of a button, positioning, power distribution circuit and other input circuits, you can press and hold the button during Siemens PLC operation; at this time, the corresponding Siemens PLC input point terminal is shorted to the common terminal, and the corresponding Siemens PLC input indicator light is on, indicating that Buttons and distribution wiring are OK.
If the electrical control cabinet is not lit, it is likely to be damaged by the button, the power distribution line is in poor contact or disconnected. Go to the next judgment, if the button is OK, then use the multimeter pen, one end is connected to the Siemens PLC input terminal, and the other end is connected to the corresponding Siemens PLC input point. Note: Do not encounter 220V or 110V input. This light is on, indicating that there is a problem with the power distribution line. The indicator light is off, indicating that the Siemens PLC input point is damaged.
3. Maintenance of output circuit
Siemens PLC output point, if the indicator light corresponding to the action object does not flash, when the Siemens PLC running state is clear, it means that the Siemens PLC output logic function of the action object is not satisfied; or, if there is a problem with the input circuit, check the input circuit as above described.
If the electrical indicator light corresponding to the control cabinet is on, but the corresponding actuators such as solenoid valve and contactor do not act, check the power supply and safety device controlled by the solenoid valve. The output point of the terminal. The iron core does not light up, it is likely to be a problem with the fuse corresponding to the power supply. When the light is on, it means that the power supply is normal, and the solenoid valve, contactor, and distribution circuit are abnormal. When the solenoid valve, contactor, power distribution circuit and other problems are eliminated and still cannot work normally, use a multimeter pen, which is shared with the corresponding output terminal, and the other end is in contact with the corresponding Siemens PLC output point. At this time, the solenoid valve still does not act. Indicates that the output line is faulty.
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