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3-1 Design Precautions
Observe the following precautions when designing a system incorporating a
CPM1 PC.
3-1-1 Power Supply Wiring
Separate the power supply wiring from the control system, CPM1 system, and
DC I/O system wiring.
3-1-2 Interlock and Limit Circuits
Construct an external interlock circuit if CPM1 outputs are used to perform recip-
rocal 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
CPM1
In the interlock circuit above, MC1 and MC2 can’t be ON at the same time even if
CPM1 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. Electrocution, product
damage and malfunction may result.
• Connecting or disconnecting Expansion I/O Units and CPU Units.
• Assembling Units
• Connecting cables and wiring.
3-1-4 CPM1 Power Interruptions
Supply Voltage Drop
When the supply voltage falls below 85% of the rated value, the PC stops and
the output goes OFF.
Momentary Power Failure Detection
A momentary power failure lasting less than 10 ms with an AC power supply and
2 ms with a DC power supply is not detected and the CPU Unit continues to oper-
ate.
A momentary power failure lasting longer than 10 ms with an AC power supply
and 2 ms with a DC power supply may or may not be detected in an uncertain
area.
When a momentary power failure is detected, the CPU Unit stops operating and
the output goes OFF.
Design Precautions Section 3-1