5
Designing the Control System is the first step in automating any process. A
PC can be programmed and operated only after the overall Control System is
fully understood. Designing the Control System requires a thorough under-
standing of the system that is to be controlled. The first step in designing a
Control System is thus determining the requirements of the controlled sys-
tem.
The first thing that must be assessed is the number of input and output points
that the controlled system will require. This is done by identifying each device
that is to send an input signal to the PC or which is to receive an output sig-
nal from the PC. Keep in mind that the number of I/O points available de-
pends on the configuration of the PC. Refer to
3–3 IR Area
for details on I/O
capacity and assigning I/O bits to I/O points.
Next, determine the sequence in which control operations are to occur and
the relative timing of the operations. Identify the physical relationships be-
tween the I/O devices as well as the kinds of responses that should occur
between them.
For instance, a photoelectric switch might be functionally tied to a motor by
way of a counter within the PC. When the PC receives an input from a start
switch, it could start the motor. The PC could then stop the motor when the
counter has received five input signals from the photoelectric switch.
Each of the related tasks must be similarly determined, throughout the entire
control operation.
The actual Units that will be mounted must be determined according to the
requirements of the I/O devices. This will include actual hardware specifica-
tions, such as voltage and current levels, as well as functional considera-
tions, such as those that require Special I/O Units or Link Systems. In many
cases, Special I/O Units or Link Systems can greatly reduce the program-
ming burden. Details on these Units and Link Systems are available in indi-
vidual
Operation Manuals
and
System Manuals.
Once the entire Control System has been designed, the task of program-
ming, debugging, and operation as described in the remaining sections of
this manual can begin.
Control System Design
Input/Output Requirements
Sequence, Timing, and
Relationships
Unit Requirements
Overview of PC Operation Section 1–5
To Next Page
Loading...
Need help?
General
