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5.3 Wiring of Input and Output
5.3.1 Input Wiring
Connection of photoelectric sensor and proximity sensor
Relay output type
NPN open collector output type
Voltage output type
Two-wire output type
Precaution when using LED-equipped reed switch
When a LED is connected in series to an input
contact such as 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.
Precaution when using two-wire type sensor
If the input of 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.
The formula is based on an input impedance of
5.6kΩ. The input impedance varies depending on
the input terminal number.
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