Wiring to I/O Modules
Wiring connections to and from user-supplied input and output field devices are made
to the detachable terminal board supplied with each I/O module. This removable
terminal board makes it easy to pre-wire field wiring to the user-supplied input and
output devices, and to replace modules in the field without disturbing existing field
The I/O terminal boards has 20 screw terminals. Each terminal accepts up to one AWG
#14 wire using ring or lug type terminals. Minimum recommended wire size is AWG
#22. These terminals require a flat or Phillips head screwdriver for installing field
wiring. An isolated 24 volt DC supply is available on the power supply. Wires are
routed to and from the terminals out of the bottom of the terminal board cavity.
Installing a Terminal Board
To install a terminal board with no wires attached:
1. Hook the hinge, located on the bottom of the terminal board, to the lower slot on
2. Push the terminal board toward the module until it snaps into place.
3. Open the terminal board cover and ensure that the latch on the module is securely
holding the terminal board in place.
Check the label on the hinged door and the label on the module to
ensure that they match. If a wired terminal board is installed on the
wrong module type, damage to the module could occur.
When installing a terminal board that has wiring attached, verify that the terminal board
is connected to the proper module type. Figure 2-3 shows the recommended procedure
for terminal board installation.
Figure 2-3. Installing a Terminal Board
Series 90-30 I/O Processor Module User’s Manual - June 1994
Removing a Terminal Board
To remove a terminal board:
1. Open the plastic terminal board cover.
2. Push up on jacking lever to release the terminal block (Figure 2-4).
3. Grasp pull-tab toward you until contacts have separated from module housing and
hook has disengaged for full removal (Figure 2-5).
Figure 2-4. Releasing the Terminal Block
Figure 2-5. Removing a Terminal Board
Chapter 2 Installation and Wiring
Field Wiring Considerations
You should calculate the maximum current for each wire and observe
proper wiring practices. Failure to do so could cause injury to
personnel or damage to equipment.
It is recommended that the following procedures be followed when routing and
connecting field wiring from user devices to the PLC or to output devices to be
controlled by the PLC.
All low level signal wires should be run separately from other field wiring.
AC power wiring should be run separately from DC field wiring.
Field wiring should not be routed close to any device that could be a potential source
of electrical interference.
If severe noise problems are present, additional power supply filtering or an
isolation transformer may be required.
Ensure that proper grounding procedures are followed to minimize potential safety
hazards to personnel.
Label all wires to and from I/O devices. Record circuit identification numbers or
other pertinent data on the inserts for the module’s faceplate door).
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