First, I know nothing about PLC's, but I was wondering is there a way
to extract data from a SQL database file, feed that to a PLC is some
manner, and then have the PLC trigger a diverter gate based on the
value in the table exceeding a certain value, to divert parts to
another location.

Am I off base, or is there something out there that will allow or help
me to do this. Any help would be greatly appreciated.

Hi

This will depend on the method the PLC is programmed. You can pull data from
a SQL Server database using many different interfaces

A starting place may be
http://msdn.microsoft.com/library/de...asp?frame=true

In general using the database as a realtime system is not what they are
designed for. You may want to implement an event from a trigger using a COM
object and the sp_OA* procedures or possibly using the existance of a file
as an event (or similar using some form of polling). It may also be possible
to do this with Notification Services
http://msdn.microsoft.com/library/de...asp?frame=true

If using a trigger you should make sure that it is not left waiting for
something to happen as this will extend the duration of your transactions.

John


"Razorbak71" <razorbak71@yahoo.com> wrote in message
news:c4aa35eb.0311061930.1262a64c@posting.google.c om...
> First, I know nothing about PLC's, but I was wondering is there a way
> to extract data from a SQL database file, feed that to a PLC is some
> manner, and then have the PLC trigger a diverter gate based on the
> value in the table exceeding a certain value, to divert parts to
> another location.
>
> Am I off base, or is there something out there that will allow or help
> me to do this. Any help would be greatly appreciated.

In article <c4aa35eb.0311061930.1262a64c@posting.google.com >, razorbak71
@yahoo.com says...
> First, I know nothing about PLC's, but I was wondering is there a way
> to extract data from a SQL database file, feed that to a PLC is some
> manner, and then have the PLC trigger a diverter gate based on the
> value in the table exceeding a certain value, to divert parts to
> another location.
>
> Am I off base, or is there something out there that will allow or help
> me to do this. Any help would be greatly appreciated.

This is done all the time in control systems - been doing it for almost
10 years myself.

There are many ways to do this, but it depends on which PLC you are
using.

Most common methods are a VB app speaking DDE to a PLC communications
app that lets you specify a address/data type.

Other methods include HMT/MMI screen applications that already have the
ability to interface with the database and PLC and act as the middle
(communications) path.

There are also things like RSSQL by AB/Rockwell that make this real
nice.

Keep in mind one thing - do not write the set-points directly to the
registers used to control the gate. Put the set-points in a holding
area, check them for valid range, then move them to the set-point area.

My email address is shown below (remove the 999) if you want to email me
about this.

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spamfree999@rrohio.com
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