Mitsubishi Electric MELSEC-A series User Manual page 37

Create a safety circuit outside the programmable controller to
DANGER
ensure the whole system will operate safely even if an
external power failure or a programmable controller failure
occurs.
Install the emergency stop switch outside the controlpanel so
that workers can operate it easily.
Otherwise, incorrect output or malfunction may cause an
accident.
(1) For an emergency stop circuit, protection circuit and
(2) When the programmable controller detects the following
(3) Depending on the failure of the output module's relay or
Design a circuit so that the external power will be supplied
after power-up of the programmable controller.
Activating the external power supply prior to the
programmable controller may result in an accident due to
incorrect output or malfunction.
If load current more than the rating or overcurrent due to a
short circuit in the load has flowed in the output module for a
long time, it may cause a fire and smoke. Provide an external
safety device such as a fuse.
For the operation status of each station at a communication
error in data link, refer to the respective data link manual.
The communication error may result in an accident due to
incorrect output or malfunction.
interlock circuit that is designed for incompatible actions
such as forward/reverse rotation or for damage
prevention such as the upper/lower limit setting in
positioning, any of them must be created outside the
programmable controller.
error conditions, it stops the operation and turn off all the
outputs.
The overcurrent protection device or overvoltage
protection device of the power supply module is
activated.
The programmable controller CPU detects an error
such as a watchdog timer error by the self-diagnostics
function.
In the case of an error of a part such as an I/O control
part that cannot be detected by the programmable
controller CPU, all the outputs may turn on. In order to
make all machines operate safely in such a case, set up
a fail-safe circuit or a specific mechanism outside the
programmable controller.
transistor, the output status may remain ON or OFF
incorrectly. For output signals that may lead to a serious
accident, create an external monitoring circuit.
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