6.4 Precautions on Wiring
6-41
6
Fig. 6.21 Connecting Inductive Loads (Sourcing Inputs)
Fig. 6.22 Connecting Inductive Loads (Sinking Inputs)
2) Leakage Current from Input Devices
When connecting an input device that exhibits leakage current during the OFF state
(such as limit switch with LEDs) to a DC Input Module, the leakage current may be
too large to stay within the OFF voltage range and the input signal may never go
OFF.
The following diagram shows when a LED-equipped limit switch with a 3-mA leak-
age current is connected to the Input Module (12/24 VDC, 16-point).
12 VDC
(24 VDC)
Flywheel diode
Inductive load
Input
Input
Common
12 VDC
(24 VDC)
Flywheel diode
Inductive load
Input
Input
Common
Input device
(limit switch with LED)
Input
DC Input Module
Leakage current = 3 mA
Input impedance
Zi
Common
Power supply
for input signal
(12/24 VDC)
