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3-1 Design Precautions
Observe the following precautions when designing a system incorporating a
CPM1A PC.
3-1-1 Power Supply Wiring
Separate the power supply wiring from the control system, CPM1A 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 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
Programmable Controller) to ensure safety in the system if an abnormality
occurs due to malfunction of the PC or another external factor affecting the PC
operation. Not providing proper safety measures may result in serious
accidents.
Construct an external interlock circuit if CPM1A outputs are used to perform
reciprocal operations such as controlling the forward and reverse operation of a
motor or if incorrect PC operation could cause accidents or mechanical damage.
Also, construct an external limit circuit to prevent run-away movement in sys-
tems such as position control.
The following diagram shows an example of an interlock circuit.
Interlock Circuit
Motor forward
Motor reverse
MC1
01005
MC2
MC2
01006
MC1
CPM1A
In the interlock circuit above, MC1 and MC2 can’t be ON at the same time even if
CPM1A outputs 01005 and 01006 are both ON (an incorrect PC operation).
3-1-3 Power Supply Voltage
Caution Use the power supply voltages indicated in Section 2 Unit Specifications and
Components. Failure to adhere to the specifications may result in fire. In places
where power supply conditions are poor, take steps to ensure that power is sup-
plied at the rated voltage. Be sure to adhere to safety precautions, such as pro-
viding breakers to prevent short circuits in external wiring. When conducting any
of the following operations, turn OFF the power to the PC. Electric shock, prod-
uct damage and malfunction may result.
• Connecting or disconnecting Expansion I/O Units and CPU Units.
• Assembling Units
• Connecting cables and wiring.
3-1-4 CPM1A Power Interruptions
Supply Voltage Drop
When the supply voltage falls below 85% of the rated value, the PC will stop and
the outputs will go OFF.
Design Precautions Section 3-1