FBM216b P0927AJ PLC/DCS control module

Description

Various brands of PLCs have self diagnosis functions, and the skill of PLC maintenance is to fully utilize its self diagnosis function to analyze the cause of faults when the PLC is abnormal. For example, when there is an abnormality in the PLC, first check the power supply voltage, whether the screws and connectors of the PLC and I/O terminals are loose, and whether there are other faults present. Then, based on the status of various LED indicators set on the basic unit of the PLC, check whether there are any abnormalities in the PLC itself and externally. PLC is essentially a computer dedicated to industrial control, with a hardware structure that is basically the same as a microcomputer.

one
PLC maintenance tips – Power indicator ([POWER] LED indicator) When power is supplied to the PLC basic unit, the [POWER] LED indicator light set on the surface of the basic unit will light up. If the power is turned on but the [POWER] LED indicator light is not on, please confirm the power wiring. In addition, if the same power supply has drive sensors, please confirm whether there is a load short circuit or overcurrent. If it is not for the above reasons, it may be due to the inclusion of conductive foreign objects or other abnormal situations in the PLC, causing the fuse in the basic unit to blow. At this time, the problem can be solved by replacing the fuse.

two
PLC Maintenance Tips – Error Indication ([EPROR] LED Flashing) When a program syntax error occurs, such as forgetting to set a timer or counter constant, or there is abnormal noise, conductive foreign objects mixed in, causing changes in the program memory content, the [EPROR] LED will flash, the PLC is in the STOP state, and all outputs will turn OFF. In this case, the program should be checked for errors and for the presence of conductive foreign objects and high-intensity noise sources.

three
PLC maintenance tips – error indication ([EPROR] LED light on). If there is a change of [EPROR] LED light on → flashing during the inspection process, please perform a program check. If the [EPROR] LED remains on all the time, please confirm if the program calculation cycle is too long and monitor D8012 to determine the maximum scanning time.

four
PLC maintenance tips – regardless of whether the LED light of the input unit is on or off, please check whether the input signal switch is indeed in the ON or OFF state. When the input switch and LED light are connected in parallel with a resistor, even if the input switch is OFF but the parallel circuit is still connected, the PLC can still be input. If input devices such as light sensors are used, the sensitivity may change due to dirt adhering to the emitting/receiving parts, which may not fully enter the “ON” state. Unable to receive ON and OFF inputs in a shorter period of time than the PLC operation cycle. When different voltages are applied to the input terminals, it can damage the input circuit.

five
The skill for PLC maintenance – whether the LED light of the output indicator output unit is on or off, if the load cannot be turned on or off, it is mainly due to overload, load short circuit, or impact current of capacitive load, which causes the output contact of the relay to bond or poor contact surface, resulting in poor contact.

matters needing attention
During the PLC maintenance process, if it is found that the power supply is burnt out, the filter electrolytic capacitor behind the rectifier bridge has exploded, and the fuse has burned black, a multimeter needs to be used to check whether the exploded filter capacitor has been short circuited. Additionally, other components need to be checked one by one to see if they are burnt out. If not, you can replace the fuse and filter electrolytic capacitor and turn them on. After checking that all power supplies are normal, install the entire machine and then turn it on for use.

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