Table of Contents
Advertisement
In the 8 DO modules, the relays of outputs 1 through 5 are Single Pole Single Throw (SPST)
normally open (NO) and are referred to as the "Form A" relays. The relays of outputs 6
through 8 are Single Pole Double Throw (SPDT) and are referred to as the "Form C" relays.
In the 16 DO modules, the relays of outputs 1 through 5 and 9 through 13 are Single Pole
Single Throw (SPST) normally open (NO) "Form A" relays. The relays of outputs 6 through 8
and 14 through 16 are Single Pole Double Throw (SPDT) "Form C" relays.
The physical position of each relay is monitored by the module logic, using a back indication
signal which is connected to the relay's second contact set. Any contradiction between the
required position and the back indication signal is reported to the CPU and is available to the
user program.
In some applications it is necessary to inhibit relay output operation when attending the site for
safety reasons. In all DO relay modules, it is possible to inhibit all relays per DO module.
When a module is configured to enable relay inhibiting, the power to the relays is provided
from the power supply via a dedicated power line (12V DO), controlled from the "12V DO"
input (TB located on the power supply module panel). When the input's terminals are shorted,
the relays are operational. When the input's terminals are open, the relays are inhibited (EE
relays in the 0 position and ML relays do not change state.)
Note: In systems with I/O expansion, the power supplies on I/O expansion frames can be
attached via DC cable to the power supply on the previous I/O expansion frame in a daisy-
chain manner, or directly to the main power supply. In this case, the 12V DO control on the
main power supply can control all DO EE relays in the entire RTU that were configured by dip
switch for 12V DO. This enables the user to inhibit all DO EE relays in the entire RTU simply
by removing the plug from the 12V DO control in the main power supply. For more
information, see the I/O Expansion and Expansion Power Supply Module chapters below.
The user program can monitor the relay inhibiting status and act accordingly. Also, when the
module's relays are inhibited, any mismatch between the relay position and the output logical
state is ignored.
Module Configuration
Relay Inhibiting
When the dip switch is set to 12V DO, the position of the 2-pin 12V DO
Control connector on the front panel of the power supply module (see
Power Supply Module chapter above) acts as a safety mechanism. When
the 2-pin TB is unplugged from the 12V DO Control (e.g. for maintenance),
power is not supplied via the motherboard to the relays and the relays are
disabled. The 12V DO affects all relays in the system that are programmed
to work from the 12V DO and not the (default) 12V Main.
EE relays that are programmed for 12V DO operation will disconnect when
9-3
Digital Output Relay Module
Advertisement
Table of Contents
