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<== Date ==> <== Thread ==>

Subject: Re: Remote I/O
From: Matthias Clausen <Matthias.Clausen@desy.de>
To: nick.rees@diamond.ac.uk
Cc: tech-talk@aps.anl.gov
Date: Wed, 16 Dec 2009 14:16:17 +0100
Hi Nick,

if you just need 'basic' communication - Ethernet would be a good choice.
Keep in mind that those Ethernet protocols are not really safe! You should run this kind of controls on a separate network and not on the control network itself. This would require a second Ethernet interface on your softIOC. Of course EtherCAT is a candidate. But you introduce another dependency to - Beckhoff. Choosing Modbus/TCP or the basic Siemens/TCP would elimitate this dependencies and you can also chosse WaGo I/O - which we are using.
We have some WaGo modules with Modbus controller running at DESY.
Also bigger Siemens PLCs are integrated via Ethernet (Siemens TCP)

In case you need deterministic communication - or you want to integrate process I/O like pressure transducers and valve positioners you might be better off with a field bus like Profibus. In our case sensors and actors are directly connected to Profibus. The remaining I/O is connected through WaGo I/O with a Profibus controller. Profibus driver and configuration is available from us - even with redundancy support... And there is a high precision temperature readout system - also for low temperatures- available with a Profibus controller. (The controller could be replaced ...)
Smaller Siemens PLCs are integrated directly into the Profibus I/O

Hope this helps.

-Matthias


nick.rees@diamond.ac.uk wrote:
At Diamond we are considering what to use for the next generation of
discrete I/O. Currently we have a lot of VME based hardware, but we are
considering a good architecture for a Linux world.

The model that we are considering is a soft IOC on a Linux system
communicating over Ethernet using an open, industry standard protocol to
distributed DIN-Rail mounted I/O points. These I/O points take in
Ethernet and are powered from a 24V bus that will run around the
hardware area.

This eliminates any dependence on a specialized bus architecture (apart
from Ethernet) on the Linux system, so they can be commodity PC's, and
hopefully allows us to use widely available, cheap, industrial modules
for I/O. It will not completely replace all of the requirements
currently serviced by VME, but would be able to satisfy most of them,
with the remaining few being serviced by the occasional VME system (or
FPGA, or some other bus, or something else entirely in the future...).

This email is to poll the EPICS community as to the experience people
have had, and recommendations for and against.

The sort of thing we have identified are:

 1. Modbus/TCP based modules, such as the Acromag Busworks series
http://www.acromag.com/models.cfm?Product_Function_ID=28&Category_ID=22&;
Group_ID=2
 2. EtherCAT base modules, such as those from Beckhoff:
http://www.beckhoff.com/
 3. Standard PLC systems where (as distinct from the other two), you
take Ethernet to a PLC controller which then has a series of modules it
talks to in a variety of possible ways.

So, is anyone willing to share their experiences with these or similar
systems,

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713



--
------------------------------------------------------------------------
Matthias Clausen                         Cryogenic Controls Group(MKS-2)
phone:  +49-40-8998-3256                Deutsches Elektronen Synchrotron
fax:    +49-40-8994-3256                                    Notkestr. 85
e-mail: Matthias.Clausen@desy.de                           22607 Hamburg
WWW-MKS2.desy.de                                                 Germany
------------------------------------------------------------------------


Replies:
Re: Remote I/O Ralph Lange
References:
Remote I/O nick.rees

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