Mitsubishi Electric MELSEC iQ-F FX5 Series User Manual page 4

[Design Precautions]
WARNING
● Make sure to set up the following safety circuits outside the programmable controller to ensure safe
system operation even during external power supply problems or programmable controller failure.
Otherwise, malfunctions may cause serious accidents.
- Emergency stop circuits, protection circuits, and protective interlock circuits (for conflicting
operations such as forward/reverse rotations or for preventing damage to the equipment such as
upper/lower limit positioning) must be configured external to the programmable controller.
- Note that when the CPU module detects an error, such as a watchdog timer error, during self-
diagnosis, all outputs are turned off. - Also, when an error occurs in an input/output control block,
where it cannot be detected by the CPU module, output control may be disabled. External circuits
and mechanisms should be designed to ensure safe machinery operation in such a case.
- Note that the output current of the 24 V DC service power supply varies depending on the mode
land the absence/presence of extension modules. If an overload occurs, the voltage automatically
drops, inputs in the programmable controller are disabled, and all outputs are turned off. External
circuits and mechanisms should be designed to ensure safe machinery operation in such a case.
- Note that when an error occurs in a relay, triac or transistor of an output circuit, the output might stay
on or off. For output signals that may lead to serious accidents, external circuits and mechanisms
should be designed to ensure safe machinery operation in such a case.
● Construct an interlock circuit in the program so that the whole system always operates on the safe
side before executing the control (for data change) of the programmable controller in operation.
Read the manual thoroughly and ensure complete safety before executing other controls (program
change, parameter change, forced output, and operation status change) to the programmable
controller in operation.
Improper operation may damage machines or cause accidents.
● In an output circuit, when a load current exceeding the rated current or an overcurrent caused by a
load short-circuit flows for a long time, it may cause smoke and fire. To prevent this, configure an
external safety circuit, such as a fuse.
● For the operating status of each station after a communication failure, refer to manuals relevant to the
network. Incorrect output or malfunction may result in an accident.
● Especially, in the case of a control from an external device to a remote programmable controller,
immediate action cannot be taken for a problem on the programmable controller due to a
communication failure. Determine the handling method as a system when communication failure
occurs along with configuration of interlock circuit on a program, by considering the external
equipment and CPU module.
● Do not write any data to the "manufacturer setting area", "system area", and "write-protect area" of the
buffer memory in the module. Executing data writing to the "manufacturer setting area", "system
area", or "write protect area" may cause malfunction of the programmable controller alarm. For the
"manufacturer setting area", "system area", or "write-protect area", refer to Page 169 Buffer
Memory and "List of Buffer Memory Addresses" in MELSEC iQ-F FX5 Motion Module/Simple Motion
Module User's Manual (Application).
● If a communication cable is disconnected, the network may be unstable, resulting in a communication
failure of multiple stations. Construct an interlock circuit in the program so that the system always
operates on the safe side even if communications fail. Incorrect output or malfunction may result in an
accident.
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