Omron CJ - 08-2008 Operation Manual page 275

Fail-safe Circuits
Interlock Circuits
An external relay (CR1) is connected to the RUN output from the Power Sup-
ply Unit as shown in the following diagram.
MCB1
MCB2
Note 1. When a Power Supply Unit without a RUN output is used, program the Al-
ways ON Flag (A1) as the execution condition for an output point from an
Output Unit.
2. Do not latch the RUN output and use it in a circuit to stop a controlled ob-
ject. Chattering of the relay contacts used in the output may cause incor-
rect operation.
When the PLC controls an operation such as the clockwise and counterclock-
wise operation of a motor, provide an external interlock such as the one
shown below to prevent both the forward and reverse outputs from turning ON
at the same time.
PLC
This circuit prevents outputs MC1 and MC2 from both being ON at the same
time even if both CIO 000500 and CIO 000501 are both ON, so the motor is
protected even if the PLC is programmed improperly or malfunctions.
CR1
Controlled system
Transformer
or noise filter
Twisted-pair wires
PLC RUN
output*
CR1
Interlock circuit
MC2
000501
MC1
000502
Section 5-1
Power supply
CJ-series PLC
+
DC voltage DC
input/output
regulator –
Surge suppressor
Motor clockwise
MC1
Motor counterclockwise
MC2
227