Chapter 8: Installation and Wiring
Do-more T1H Series PLC User Manual, 1st Edition, Rev. C
8-25
In some cases, using the built-in aux24VDC supply can result in a cost savings for
your control system. It can power combined loads up to 500mA if power budget allows. Be
careful not to exceed the current rating of the supply. If you are the system designer for your
application, you may be able to select and design in field devices which can use the +24VDC
auxiliary supply.
Powering I/O Circuits with the Auxiliary Supply
All AC power supplies feature an internal auxiliary supply. If input devices AND output
loads need +24VDC power, the auxiliary supply may be able to power both circuits as shown
in the following diagram.
DC-powered units are designed for application environments in which low-voltage DC
power is more readily available than AC. These include a wide range of battery-powered
applications, such as remotely-located control, in vehicles, portable machines, etc. For this
type of application, all input devices and output loads typically use the same DC power
source. Typical wiring for DC-powered applications is shown in the following diagram.
Input Module
Auxiliary
+24 VDC
Supply
Power Input
Output Module
Loads
AC Power
+
–
Inputs
Com.
Outputs Com.
Input Module
Power Input
Output Module
Loads
DC Power
+
–
+
–
Inputs
Com.
Outputs Com.
