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Design Precautions
Section 3-1
3-1
Design Precautions
Observe the following precautions when designing a system incorporating a
CPM2B PLC.
3-1-1
Power Supply Wiring
Separate the power supply wiring from the power system, control system,
CPM2B system, and DC I/O system wiring. Separate the control circuits that
supply power to the main Unit from the main circuits using dedicated circuit
protectors and fuses.
3-1-2
Power Supply Voltage
!Caution
Use the power supply voltages indicated in Section 2-1 Specifications. Failure
to adhere to the specifications may result in fire.
If the power supply voltage falls below 85% of the rated voltage, the CPM2B
will stop and all outputs will be turned OFF. If low voltage affects the equip-
ment, etc., provide a protection circuit which shuts off the output until the sup-
ply voltage returns to the rated value.
In places where power supply conditions are poor, take steps to ensure that
power is supplied at the rated voltage. Be sure to adhere to safety precau-
tions, such as providing breakers to prevent short circuits in external wiring.
When conducting any of the following operations, turn OFF the power to the
PLC. Electrocution, product damage and malfunction may result.
• Connecting or disconnecting Expansion I/O Boards and CPU Boards.
• Assembling equipment.
• Connecting cables and wiring.
3-1-3
Interlock and Limit Circuits
!WARNING
Emergency stop circuits, interlock circuits, limit circuits, and similar safety
measures must be provided in external control circuits (i.e., not in the Pro-
grammable Controller) to ensure safety in the system if an abnormality occurs
due to malfunction of the PLC or another external factor affecting the PLC
operation. Not providing proper safety measures may result in serious acci-
dents.
The following diagram shows an example of an interlock circuit.
In the interlock circuit above, MC1 and MC2 can’t be ON at the same time
even if CPM2B outputs 01005 and 01006 are both ON (an incorrect PLC
operation).
Interlock Circuit
Motor forward
Motor reverse
CPM2B
01005
01006
MC1
MC2
MC2
MC1
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