Mitsubishi Electric MELSEC-Q Series User Manual page 3

[Design Precautions]
• When overcurrent which exceeds the rating or caused by short-circuited load flows in the output
module for a long time, it may cause smoke or fire. To prevent this, configure an external safety
circuit, such as fuse.
• Build a circuit that turns on the external power supply when the PLC main module power is
turned on. If the external power supply is turned on first, it could result in erroneous output or
erroneous operation.
• When there are communication problems with the data link, refer to the corresponding data link
manual for the operating status of each station.
Not doing so could result in erroneous output or erroneous operation.
• When connecting a peripheral device to the CPU module or connecting a personal computer or
the like to the intelligent function module to exercise control (data change) on the running PLC,
configure up an interlock circuit in the sequence program to ensure that the whole system will
always operate safely.
Also before exercising other control (program change, operating status change (status control))
on the running PLC, read the manual carefully and fully confirm safety.
Especially for the above control on the remote PLC from an external device, an immediate
action may not be taken for PLC trouble due to a data communication fault.
In addition to configuring up the interlock circuit in the sequence program, corrective and other
actions to be taken as a system for the occurrence of a data communication fault should be
predetermined between the external device and PLC CPU.
• Do not bunch the control wires or communication cables with the main circuit or power wires, or
install them close to each other. They should be installed 100 mm (3.94 inch) or more from each
other.
Not doing so could result in noise that would cause erroneous operation.
• When controlling items like lamp load, heater or solenoid valve using an output module, large
current (approximately ten times greater than that present in normal circumstances) may flow
when the output is turned OFF to ON.
Take measures such as replacing the module with one having sufficient rated current.
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DANGER
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CAUTION
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