Omron SYSMAC CS1D-PD Series Operation Manual page 233

Wiring Methods
AC Input Units
Precautions when
Connecting a Two-wire DC
Sensor
1,2,3...
• 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 ON
I = (V – V
ON CC
When I is smaller than I
ON
bleeder resistor constant can be calculated as follows:
R ≤ (V
– V
CC R
Power W ≥ (V
3. Relation between current when the PLC is OFF and sensor leakage cur-
rent:
≥ I
I
OFF leak
If I is larger than I
leak
constant can be calculated as follows:
R ≤ R × V
IN OFF
Power W ≥ (V
IN
AC Input Unit
COM
IN
AC Input Unit
COM
R
≤ I
(max.)
OUT
– 1.5 [PLC internal residual voltage])/R
R
(min), connect a bleeder resistor R. The
OUT
)/(I (min.) – I )
OUT ON
2
/R × 4 [allowable margin]
– V )
CC R
, connect a breeder resistor. The breeder resistor
OFF
× R
/(I – V )
leak IN OFF
2
/R × 4 [allowable margin]
– V )
CC R
Section 5-4
IN
193