Connecting Dc I/O To "Solid State" Field Devices - Automation Direct DL205 Manual

Connecting DC I/O In the previous section on Sourcing and Sinking concepts, the DC I/O circuits were
to "Solid State" explained to only allow current to flow one way. This is also true for many of the field
devices which have solid-state (transistor) interfaces. In other words, field devices
Field Devices
can also be sourcing or sinking. When connecting two devices in a series DC circuit,
one must be wired as sourcing and the other as sinking.
Solid State Several DL205 DC input modules are flexible because they detect current flow in
Input Sensors either direction, so they can be wired as either sourcing or sinking. In the following
circuit, a field device has an open-collector NPN transistor output. It sinks current
from the input point, which sources current. The power supply can be the +24
auxiliary supply or another supply (+12 VDC or +24VDC), as long as the input
specifications are met.
In the next circuit, a field device has an open-emitter PNP transistor output. It
sources current to the input point, which sinks the current back to ground. Since the
field device is sourcing current, no additional power supply is required.
Solid State Sometimes an application requires connecting an output point to a solid state input
Output Loads on a device. This type of connection is usually made to carry a low-level control
signal, not to send DC power to an actuator.
Several of the DL205 DC output modules are the sinking type. This means that each
DC output provides a path to ground when it is energized. In the following circuit, the
output point sinks current to the output common when energized. It is connected to a
sourcing input of a field device input.
DL205 System DC Sinking Output
Field Device
Output
(sinking)
Supply
–
Ground
Field Device
+V
Output (sourcing)
Ground
Power
+DC pwr
Output
(sinking)
Common
I/O Wiring and Specifications
DL205 System DC Input
Input
(sourcing)
+
Common
DL205 System DC Input
Input
(sinking)
Common
Input
(sourcing)
+
10–30 VDC
– Ground
DL205 Installation and I/O Manual, Rev. B
3–7
Field Device
+V