Mitsubishi Electric LCPU-U-HW Safety Manuallines page 5

[Design Precautions]
Precautions for using digital-analog converter modules
and analog input/output modules
● When a module is faulty, analog outputs may remain on. Configure an external
circuit for monitoring output signals that could cause a serious accident.
Precautions for using high-speed counter modules and
flexible high-speed I/O control modules
● Outputs may remain on or off due to a failure of a transistor for external output.
Configure an external circuit for monitoring output signals that could cause a
serious accident.
Precautions for using positioning modules
● Configure safety circuits external to the programmable controller to ensure
that the entire system operates safely even when a fault occurs in the external
power supply or the programmable controller. Incorrect output or malfunction
due to a communication failure may result in an accident.
(1) Machine OPR (Original Point Return) is controlled by two kinds of data: an
OPR direction and an OPR speed. Deceleration starts when the near-point
watchdog signal turns on. If an incorrect OPR direction is set, motion
control may continue without deceleration. To prevent machine damage
caused by this, configure an interlock circuit external to the programmable
controller.
(2) When the module detects an error, the motion slows down and stops or the
motion suddenly stops, depending on the stop group setting in parameter.
Set the parameter according to the positioning system specifications. In
addition, set the OPR parameter and positioning data within the parameter
setting range.
(3) Outputs may remain on or off, or be undefined due to a failure of a
component such as an insulated element or transistor in an output circuit,
where the CPU module cannot detect any error. Configure an external
circuit for monitoring output signals in a system where an incorrect output
could cause a serious accident.
● An absolute position restoration by the positioning function may turn off the
servo-on signal (servo off) for approximately 60ms + scan time, and the motor
may run unexpectedly. If this causes a problem, provide an electromagnetic
brake to lock the motor during absolute position restoration.
WARNING
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