Panasonic AFP7X16DW User Manual page 39

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.
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 input unit (AFP7X16DW)
(Off voltage: 2.5 V; input impedance: 3.6kΩ)
I: Sensor's leakage current (mA)
R: Bleeder resistor (kΩ)
The off voltage of the input is 2.5 V. Therefore, select an R so that the voltage
between the COM terminal and the input terminal will be less than 2.5 V.
The input impedance is 3.6kΩ.
3.6R
I ×
3.6+R
The wattage W of the resistor is:
In the actual selection, use a value that is 3 to 5 times the value of W.
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9
≤2.5. Therefore, R≤
3.6I-2.5
(Power supply voltage)
W=
3.1 Precautions on Wiring
(kΩ)
2
R
3-3