Experimental Physics and
Industrial Control System

Pete Jemian <[email protected]> · Tue, 5 Apr 2016 08:08:58 -0500

Florian:

One reason, perhaps the major reason, why PLCs are chosen for safety

systems and also for equipment protection systems is that they are

high-availability systems. The PLC can be relied upon to do its simple

job a much greater fraction of time than many other types of controls.

Additionally, PLCs have simple operating systems and easy control of

individual bits, making it simple to interface switches and buttons.

These aspects and more are what keeps the amount of necessary routine

system maintenance is quite low and the availability high.

Also, it is common that some of the bit outputs of PLCs are chosen so

that they do not change state on system restart (but this is not unique

to PLCs).

For monitoring (or controlling) a vacuum system, a PLC is a great

choice. The logic is clear and, with clear design of the specific

system, there is no risk that some other task will interfere with the

designed control of the vacuum system. Except for hardware failure of

sensors, switches, buttons, PLC, power, ...

EPICS IOCs are not expected to have the same high-availability fraction

as PLCs.

Pete

On 2016-04-05 2:52 AM, Florian Feldbauer wrote:

Hey all,

I'm working with EPICS now for several years to develop parts of the
Detector Control System for
the PANDA experiment.
For our luminosity detector we need to control a small vacuum system.
I had a look at various talks from EPICS meetings to see, how others are
building their control systems
and I have a question concerning this:
All the systems I have seen are using PLCs to control the valves of the
system.

What is the advantage of a PLC for controlling the valves?
Why not using an EPICS IOC for direct control running on a realtime system?

I never worked on vacuum systems before, and our vacuum workshop here at
Mainz
could not help me with this question.

Many thanks in advance for the help!

   Florian

--
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Pete R. Jemian, Ph.D.                <[email protected]>
Beam line Controls and Data Acquisition, Group Leader
Advanced Photon Source,   Argonne National Laboratory
Argonne, IL  60439                   630 - 252 - 3189
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   Education is the one thing for which people
      are willing to pay yet not receive.
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System