Panasonic fp2/fp2sh User Manual page 150

Installation and Wiring
4.3 Wiring Input and Output
Connection of LED-equipped Limit Switch
With the LED-equipped limit switch, if the input of the PLC is not turned off or if the LED
of the limit switch is kept on because of the leakage current, 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)
LED-equipped
limit switch
r
Internal circuit
r: Internal resistor of limit switch (kΩ)
R: Bleeder resistor (kΩ)
The off voltage of the input is 2.5V, therefore when the power supply voltage is 24V, select R
so that
the current will be greater than I =
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.
4 − 20
Input
terminal
Bleeder
R
DC
resistor
Input unit
COM
24 - 2.5
r
(Power supply voltage)
7.5
(kΩ)
3 × I−2.5
2
R
FP2/FP2SH