Panasonic FPS Series, User Manual

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Installation and Wiring
FP Σ User's Manual
84
Precaution when using an LED-equipped Reed switch
When an LED is connected in series to an input contact such as an LED-equipped Reed
switch, make sure that the ON voltage applied to the PLC input terminal is greater than 21.6V
DC. In particular, take care when connecting a number of switches in series.
COM
+
24V
1
2
3
4
A LED-equipped Reed switch
2
Contact
B
FP Σ
3
≥ 21.6V
1
LED
4
Input terminal
Precaution when using a two-wire type sensor
If the input of the PLC does not turn off because of leakage current from the two-wire type
sensor (photoelectric sensor or proximity sensor), the use of a bleeder resistor is
recommended, as shown below.
COM
+
R
1
2
3
A
Two-wire type sensor
2
Bleeder resistor
B
FP Σ
3
Input terminal
1
Internal circuit
The formula is based on an input impedance of 5.6k
Ω
. The input impedance varies depending
on the input terminal number.
The off voltage of the input is 2.4V. Therefore, select a bleeder resistor value R so that the
voltage between the COM terminal and the input terminal will be less than 2.4V.
I x
5.6R
5.6R + R
≤ 2.4
Therefore:
(k
Ω
)
13.44R
5.6I - 2.4
R ≤
The wattage W of the resistor is:
(V) 2
R
W =
V = Power supply voltage