EPICS Controls Argonne National Laboratory

Experimental Physics and
Industrial Control System

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

Subject: RE: Equipment Availability
From: "Dalesio, Leo `Bob`" <[email protected]>
To: "David Dudley" <[email protected]>, <[email protected]>
Date: Tue, 5 Sep 2006 14:47:20 -0700
This is really your call - but the way that drivers interface to the database is one of the differences between the TIS4000 and EPICS. Without looking at it, I would say that the protocol is implemented in the driver - so I would take the TIS4000 driver and use the Allen Bradlay Control Logix device support and figure out what calls need to be replaced in the device support to call the correct routines in the driver. Most of the TIS4000 drivers use special addresses for diagnostic information - like communication errors, disconnects, etc... The Control Logix Driver takes into account the possibility that some other PLC master can change the value of an analog output. I don't know if the TIS 4000 drivers took care of this situation. I think their assumption was that the IOC was the only master of the PLC. I don't know if this is a feature that you need.
Bob 

-----Original Message-----
From: David Dudley [mailto:[email protected]] 
Sent: Tuesday, September 05, 2006 2:40 PM
To: [email protected]
Subject: RE: Equipment Availability

I see that TIS-4000 had almost all the drivers I'm looking for.  Would it be easier to port one of those drivers to the newer EPICS, or easier to take an existing driver and gut the internals to make it work with the hardware I have?

David Dudley

>>> Steven Hartman <[email protected]> 09/05/06 4:12 PM >>>
On Tue, 5 Sep 2006, David Dudley wrote:

> I spent 3 or 4 days looking for I/O cards for VME or compactPCI, and 
> have discovered that there are very few industrial I/O cards offered.
> Industrial cards are usually optically isolated, and directly handle 
> 110VAC on inputs and outputs, and the analogs all handle 4-10ma 
> current loops without converters.  You can use a simple resistor for 
> converting an input (technically considered a 'kludge' by most in 
> industrial working circles), but analog outputs generally take special 
> adapters to convert from voltage to current.

I would second Bob Dalesio's recommendation to try and get EPICS working with your existing I/O first. But there are some VME based modules which are better suited for an industrial environment. VMIC has some opto-isolated digital I/O (BI and BO) at 110 VAC, and their 4120 is a 12-bit DAC with 0-20 mA or 4-20 mA outputs. For analog inputs, I have used a resistor across my input and don't consider it too bad of kludge, but there are some ADCs which will take a 4-20 mA input.

In terms of numbers, most I/O channels in an accelerator controls system are rather slow (most between 1 and 10 Hz here). The high sampling-rate applications just get all of the attention <g>.

--
Steve Hartman
[email protected] || 919-660-2650
Duke Free Electron Laser Laboratory




References:
RE: Equipment Availability David Dudley

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