PLC present abnormal alarm, 8 types of common error parsing -

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PLC is widely used in industrial control industry, also often appear unable to work normally. Through this article, let you solve the problem of PLC for the most part.

various brands of PLC has self-diagnosis function, but PLC controller repair skill lies in, use the function is analyzed, and then accurately to find the problem. When we present abnormal alarm when the PLC controller, PLC repair personnel need to understand the eight types of common mistakes.

a abnormal, CPU

when the CPU abnormal alarm, should check the CPU unit cohesion in all the equipment inside the bus. Specific sequence method is used to replace unit there may be problems, find out the problem unit, and corresponding processing.

2, storage of abnormal alarm in abnormal

memory, if is a problem of program memory, after start programming still couldn't solve, this situation may be noise trouble cause the change of the program, otherwise should replace the memory.

3, abnormal input/output unit, expansion unit such alarm when abnormal

attack, should first check the input/output unit and extension unit cohesion, cohesion, cable connection conditions, conclude that problem after onset of a unit, to replace the unit.

4, not executable program

general conditions can be in accordance with the input - — Program execution - — The output of the process view (

1) Input view is to use the input LED lights to identify, or use the writer composed of input monitor view. When the input LED not bright, can begin to conclude that external input system, combined with multimeter to check. If the output voltage is not normal, it can be concluded that the input unit. Appeared when the LED light and the internal monitor, can be considered as input unit, CPU unit or expansion unit.

( 2) Program view is a writer on the monitor to view. Do not match the contact status and results when the ladder diagram, is a program error ( Such as the internal relay two layers of use, etc. ) Problems, or computation.

because PLC models is different, is not the same as the I/O method of linking to the LED ( Some on the unit I/O interface, some pick up on the I/O unit) 。 So, on the basis of the LED discriminant problem size are different. Five, part of the program does not perform

check method is the same as previous one, but, if the counter, stepping controller input time too short, will present no echo problems, then should check whether the input moment is enough big, check according to the input ( The biggest echo time + input unit operation scanning time multiplied by 2) The link.

power short time off, program content will disappear

1) First check to see if the battery has a problem.

( 2) After repeated on-off PLC controller itself the power to see. For the microprocessor start correctly, PLC in the early makes reset circuit and power supply circuit disconnected preservation program. This circuit attacks, will not be able to save the program. So can cut power tong, to look at it.

( 3) If in the replacement battery is still present after abnormal alarm, can determine is memory or external circuit caused by the leakage current increases exceedingly.

( 4) Power on and off always with synchronous machine system, and then can see the noise of the machine system attack. Due to the power supply system of disconnect is often associated with the machine work problems at the same time, because most of the motor windings or attack by strong noise. Seven, PROM cannot work

check the PROM connections are in good condition, and then determine whether need to replace the chip.

8, power supply, after restart or reset action stop

this problem can be considered noise trouble or PLC internal caused by the poor contact. Noise reasons are generally small and medium-sized capacitance circuit board decrease caused by the dysfunction or component, the cause of poor contact can be used to check the body after a light tap PLC and also check the cable and adapter connection status.

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