Omron SYSMAC C200H, Руководство по эксплуатации

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1-1 Overview
A PC (Programmable Controller) is basically a CPU (Central Processing Unit)
containing a program and connected to input and output (I/O) devices. The
program controls the PC so that when an input signal from an input device
turns ON, the appropriate response is made. The response normally involves
turning ON an output signal to some sort of output device. The input devices
could be photoelectric sensors, pushbuttons on control panels, limit switches,
or any other device that can produce a signal that can be input into the PC.
The output devices could be solenoids, switches activating indicator lamps,
relays turning on motors, or any other devices that can be activated by sig-
nals output from the PC.
For example, a sensor detecting a passing product turns ON an input to the
PC. The PC responds by turning ON an output that activates a pusher that
pushes the product onto another conveyor for further processing. Another
sensor, positioned higher than the first, turns ON a different input to indicate
that the product is too tall. The PC responds by turning on another pusher
positioned before the pusher mentioned above to push the too-tall product
into a rejection box.
Although this example involves only two inputs and two outputs, it is typical of
the type of control operation that PCs can achieve. Actually even this exam-
ple is much more complex than it may at first appear because of the timing
that would be required, i.e., “How does the PC know when to activate each
pusher?” Much more complicated operations, however, are also possible.
The problem is how to get the desired control signals from available inputs at
appropriate times.
To achieve proper control, the C200H uses a form of PC logic called ladder-
diagram programming. This manual is written to explain ladder-diagram pro-
gramming and to prepare the reader to program and operate the C200H.
1-2 The Origins of PC Logic
PCs historically originate in relay-based control systems. And although the
integrated circuits and internal logic of the PC have taken the place of the
discrete relays, timers, counters, and other such devices, actual PC opera-
tion proceeds as if those discrete devices were still in place. PC control, how-
ever, also provides computer capabilities and accuracy to achieve a great
deal more flexibility and reliability than is possible with relays.
The symbols and other control concepts used to describe PC operation also
come from relay-based control and form the basis of the ladder-diagram pro-
gramming method. Most of the terms used to describe these symbols and
concepts, however, have come in from computer terminology.
The terminology used throughout this manual is somewhat different from re-
lay terminology, but the concepts are the same.
The following table shows the relationship between relay terms and the PC
terms used for OMRON PCs.
Relay term PC equivalent
contact input or condition
coil output or work bit
NO relay normally open condition
NC relay normally closed condition
Relay vs. PC Terminology
The Origins of PC Logic
Section 1-2