DC Input Wiring Methods
CLICK PLCs and I/O modules with DC inputs can be wired as either
sinking or sourcing inputs. The dual diodes (shown in this diagram)
allow current to ο¬ow in either direction. Inputs grouped by a common
point must be either all sinking or all sourcing. DC inputs typically
operate in the range of +12-24 VDC.
Sinking Input Sensor (NPN Type) to PLC Sourcing Input
In the following example, a ο¬eld device has an open-collector NPN
transistor output. When energized, it sinks current to ground from the DC input point. The
PLC input current is sourced from the common terminal connected to power supply (+).
Sourcing Input Sensor (PNP Type) to PLC Sinking Input
In the following example, a ο¬eld device has an open-emitter PNP transistor output. When
energized, it sources current to the PLC input point, which sinks the current to ground. Since
the ο¬eld device loop is sourcing current, no additional power supply is required for the module.
DC Output Wiring Methods
CLICK PLCs and I/O modules with DC output circuits are wired as all current sinking only
or current sourcing only depending on which PLC or output module part number is used. DC
outputs typically operate in the range of +5-24 VDC.
PLC Sinking Output to Sourcing Load Device
Many applications require connecting a PLC output point to a DC input on a ο¬eld device load.
This type of connection is made to carry a low-level DC signals.
In the following example, the PLC output point sinks current to ground (common) when
energized. The output is connected to a ο¬eld device load with a sourcing input.
PLC DC Input
Common
Input
Field Device
PLC DC Input
Output (sourcing)
Ground Common
=>
Input
(sinking)
DC PNP Sensor
(Sourcing)
PLC Input
(Sinking)
+
β
Output
Ground Common
Supply
(sinking)
Input
(sourcing)
DC NPN Sensor
(Sinking)
PLC Input
(Sourcing)
Field Device
=>
PLC DC Output
+DC Power
+
β
Power
20-28 VDC
Output
(sinking)
Common
Input
(sourcing)
Ground
CLICK PLC Hardware User Manual, 5th Edition, Rev. F β C0-USER-M
3β30
Chapter 3: Installation and Wiring