User manual

63
Cautions when using limit switch with LED
Use a breeder resistor as below when the leakage current from limit
switch with LED keeps flowing into the PLC or LED is accidentally
turned on.
Limit switch with LED
DC 12-24V type input unit
(OFF voltage 2.5V, input impedance 3 KΩ)
r: Internal resistance of limit switch (KΩ)
R: Breeder resistance (KΩ)
Since the OFF voltage of the input is 2.5V, set R to get the following
current,
when the power supply voltage is 24V. Once calculating I, follow the
same steps as those for 2 wired sensors described on the previous
page.
DC input unit
Breeder
resistor
Internal Circuit
Input
terminal
COM
terminal
24 - 2.5
I = or more
R
7. 5
R
≤ (KΩ)
3I-2.5
(Power supply voltage)
2
W = x (3 to 5 times)
R