Omron WIRED REMOTE I-O System Manual page 15

Remote I/O Systems
1-1 Remote I/O Systems
Slave Rack
Processing
machine
Assembly line
Sensor
2
Assembly lines are often extremely long, making it difficult if not impossible to
wire all I/O devices directly from CPU Racks or Expansion I/O Racks. A Re-
mote I/O System can be used to solve this problem. In a Remote I/O System,
a Rack can be located farther from the CPU Rack than is possible with Ex-
pansion I/O Racks connected directly to the CPU Rack.
By locating a Rack farther from the CPU Rack, a Remote I/O System elimi-
nates the time and mess in wiring (or changing wiring) to many devices that
are separated from the CPU Rack. Although all I/O points must ultimately be
wired individually, the question is one of distance: Do you want to wire doz-
ens of terminals all the way across a factory complex or do you want to run a
single cable for most of the distance and then wire individual terminals lo-
cally?
The following diagram illustrates how a simple Remote I/O System would be
set up. Slave Racks, described below, are controlled by the CPU Unit
through the Master. The dotted circles show the devices that would be con-
trolled through the Units on each Rack.
Slave
Processing
machine
Processing
machine
Slave Rack
Wiring distance could also be reduced by placing an independent CPU Rack
near every location that required control, but in doing so, each PC would
have to be programmed independently and the activities of all the PC pro-
grams would need to be coordinated, a very difficult job. Here too, a Remote
I/O System simplifies the task by allowing a single CPU Unit, and thus a sin-
gle program, to integrate control of the entire process. A Remote I/O System
thus has these two advantages: Racks can be located a greater distance
from the CPU Rack and coordinating control actions is simplified because all
control is exerted by one program.
A third advantage of Remote I/O Systems is reduced noise interference. This
is the result of the single cable that replaces the otherwise numerous wires
that would be required all the way from the CPU and Expansion I/O Racks to
the I/O devices.
Master
Processing
machine
Sensor Sensor
Slave
Section 1-1
CPU Rack