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ROC800-Series Instruction Manual
4-14
Input/Output Modules
Revised Jul-14
configured to either retain the last value on reset or use a user-specified
fail-safe value.
The DO module provides LEDs that light when each output is active.
When a request is made to change the state of a DO, the request is
immediately sent to the DO module. There is no scan time associated
with a DO. Under normal operating conditions, the DO channel
registers the change within 2 milliseconds.
If the DO is in momentary or toggle mode, you can enter a minimum
time-on of 4 milliseconds.
Figure 4-13
displays the field wiring connections to the output circuit of
the DO module.
Caution
The Discrete Output module is an open-drain type output. It is not
capable of sourcing current or voltage to a load. Do not directly connect
a power source to the terminal block.
DO modules draw power for the active circuitry from the backplane,
and are current-limited for protection against excessive current.
Note
:
When using the Discrete Output module to drive an inductive
load (such as a relay coil), place a suppression diode across the
input terminals to the load. This protects the module from the
reverse Electro-Motive Force (EMF) spike generated when the
inductive load is switched off.
Figure 4-13. Discrete Output Module Field Wiring
Caution
You can induce ground loops by tying commons from various modules
together.
+V
s
CONTROL
+
-
EXTERNALLY POWERED
DISCRETE DEVICE
+
-
-
COM
COM
COM
COM
COM
DO
2+
3+
4+
5+
1+
5 CHAN
DOC0508A
Representative
Internal Circuit
Field Wiring