Safety Precautions - Mitsubishi MELSEC-Q Series User Manual

Before using this product, please read this manual and the relevant manuals introduced in this manual
carefully and pay full attention to safety to handle the product correctly.
The instructions given in this manual are concerned with this product. For the safety instructions of the
programmable controller system, please read the CPU module user's manual.
In this manual, the safety instructions are ranked as "DANGER" and "CAUTION".
!
DANGER
! CAUTION
Note that the CAUTION level may lead to a serious consequence according to the circumstances.
!
Always follow the instructions of both levels because they are important to personal safety.
Please save this manual to make it accessible when required and always forward it to the end user.
[Design Instructions]
• Install a safety circuit external to the PLC that keeps the entire system safe if there are problems
with the external power supply or PLC. Not doing so may cause false output or malfunction,
leading to accidents.
(1) Outside the PLC, construct mechanical damage preventing interlock circuits, e.g. emergency
stop circuits, protective circuits, forward/reverse or other conflicting operation interlocking
circuits, and upper and lower positioning limit switches.
(2) When the PLC detects either of the following problems, it will stop arithmetic operation and
turn off all outputs in the case of (a). In the case of (b), it will stop arithmetic operation and
hold or turn off all outputs according to the parameter setting.
(a) The overcurrent protection or overvoltage protection of the power supply module is
activated.
(b) The self-diagnostic function of the PLC CPU has detected a fault such as the watchdog
timer error.
In addition, all outputs may be turned on when there are problems undetectable by the PLC
CPU, such as in the I/O controller. Build a fail-safe circuit or provide a mechanism externally
of the PLC to operate the machine safely at such times. Refer to the CPU module user's
manual for fail-safe circuit examples.
(3) Output could be left on or off when there is trouble in the output module's relays, transistors,
etc. So build an external monitoring circuit that will monitor any output signal that could lead
to a serious accident.
A - 1
• SAFETY PRECAUTIONS •
(Always read these instructions before using this equipment.)
Indicates that incorrect handling may cause hazardous conditions,
resulting in death or severe injury.
Indicates that incorrect handling may cause hazardous conditions,
resulting in medium or slight personal injury or physical damage.
DANGER
!
A - 1