Panasonic fp2/fp2sh User Manual page 149

FP2/FP2SH
Connection of LED-equipped Reed Switch
With a LED is connected to an input contact such as LED-equipped reed switch, make
sure that the voltage value applied to the input terminal of PLC is greater than on voltage
value.
In particular, take care when connecting a number of switches in series.
LED
LED-equipped
reed switch
Contact
Connection of Two-wire Type Sensor
If the input of the PLC is not turned off because of leakage current from the two-wire
type sensor, the connection of a bleeder resistor is recommended, as shown below.
Using 16-point type DC input unit (FP2−X16D2)
(Off voltage: 2.5V, Input impedance: 3kΩ)
Two-wire
type sensor
Internal
circuit
I: Sensor's leakage current (mA)
R: Bleeder resistor (kΩ)
The off voltage of the input is 2.5V, therefore, select an R value so that the voltage between
the COM terminal and the input terminal will be less than 2.5V.
The input impedance is 3kΩ.
The resistance R of the bleeder resistor is: R ≦
The wattage W of the resistor is: W=
In the actual selection, use a value that is 3 to 5 times the value of W.
Input
terminal
On voltage
value or more
COM
Power supply for input
Input terminal
Bleeder
R
resistor
COM
(Power supply voltage)
4.3
DC
input unit
DC
input unit
7.5
(kΩ)
3 × I−2.5
2
R
Installation and Wiring
Wiring Input and Output
4 − 19