Omron CS1D DUPLEX SYSTEM - 10-2009 Operation Manual page 220

Wiring Methods
Output Wiring Precautions
Output Short-circuit
Protection
Transistor Output
Residual Voltage
Output Leakage Current
184
Two-wire sensor
V : Power voltage
CC
V : PLC ON voltage
ON
V : PLC OFF voltage
OFF
I : PLC ON current
ON
I : PLC OFF current
OFF
R : PLC input impedance
IN
4. Precautions on Sensor Surge Current
An incorrect input may occur if a sensor is turned ON after the PLC has
started up to the point where inputs are possible. Determine the time re-
quired for sensor operation to stabilize after the sensor is turned ON and
take appropriate measures, such as inserting into the program a timer de-
lay after turning ON the sensor.
Example
In this example, the sensor's power supply voltage is used as the input to
CIO 000000 and a 100-ms timer delay (the time required for an OMRON
Proximity Sensor to stabilize) is created in the program. After the Comple-
tion Flag for the timer turns ON, the sensor input on CIO 000001 will cause
output bit CIO 000100 to turn ON.
000000
TIM
0000
#0001
TIM0000 000001
000100
If a load connected to the output terminals is short-circuited, output compo-
nents and the and printed circuit boards may be damaged. To guard against
this, incorporate a fuse in the external circuit. Use a fuse with a capacity of
about twice the rated output.
A TTL circuit cannot be connected directly to a transistor output because of
the transistor's residual voltage. It is necessary to connect a pull-up resistor
and a CMOS IC between the two.
If a Triac Output Unit is used to drive a low-current load, the leakage current
may prevent the output device from turning OFF. To prevent this, connect a
bleeder resistor in parallel with the load as shown in the following diagram.
OUT
SYSMAC
COM
DC Input Unit
V R R
IN
R
V
CC
V : Sensor output residual current
R
I : Sensor control current (load current)
OUT
I : Sensor leakage current
leak
R: Bleeder resistance
L
Load power
supply
Bleeder resistor
Section 5-4