Omron CJ - 09-2009 Operation Manual page 322

Wiring
AC Input Units
Precautions when
Connecting a Two-wire DC
Sensor
1,2,3...
274
The following types of AC input devices can be connected.
Contact output
AC Switching
Proximity
switch
main
circuit
Note When using a reed switch as the input contact for an AC Input Unit, use a
switch with an allowable current of 1 A or greater. If Reed switches with
smaller allowable currents are used, the contacts may fuse due to surge cur-
rents.
When using a two-wire sensor with a 12-V DC or 24-V DC input device, check
that the following conditions have been met. Failure to meet these conditions
may result in operating errors.
1. Relation between voltage when the PLC is ON and the sensor residual
voltage:
≤ V
V – V
ON CC
2. Relation between voltage when the PLC is ON and sensor control output
(load current):
(min) ≤ I
I
OUT
I = (V – V
ON CC
When I is smaller than I
ON
bleeder resistor constant can be calculated as follows:
R ≤ (V
– V
CC
Power W ≥ (V
3. Relation between current when the PLC is OFF and sensor leakage cur-
rent:
≥ I
I
OFF leak
Connect a bleeder resistor if I
equation to calculate the bleeder resistance constant.
R
≤ I
(max.)
ON OUT
– 1.5 [PLC internal residual voltage])/R
R
(min), connect a bleeder resistor R. The
OUT
)/(I (min.) – I )
R OUT ON
2 /R × 4 [allowable margin]
– V )
CC R
is greater than I
leak
Section 5-3
IN AC Input Unit
COM
IN AC Input Unit
COM
IN
. Use the following
OFF