RS-232 Communication on the SLC-500 Help needed

Hi, I just joined the forum, to hopefully help point me in the right direction regarding a project I'm working on.

I'm a Windows application developer/database administrator for a manufacturing company. I set up a manuafcturing database for various process parameters.

Currently, these parameters are entered by hand. However, I've been working with maintenance & they tell me we have a Allen Bradley SLC-500 with an RS 232 port for serial communication.

I would like to write a small Visual Basic application to poll the SLC-500 to retrieve the data automatically & store it in our database. I only need a "read only" situation; I will not be attempting to write data back to the controller.

Is this a fairly simple task? Are there any dangers asscociated with doing something like this? Any resources that anyone can point me to? I know next to nothing about PLCs.


Any help anyone might provide would be most appreciated.

Thanks,

Jim

No, it isn't simple, and yes, it can be dangerous.

I suggest you get your controls engineering consultant or in-house PLC jock involved. The best way is to use an Allen Bradley program to use DDE or OPC links into your program. Allen Bradley tends to be very protective of their communications protocols.

What you are looking for is the DF1 protocol.
It is simple for me to implement DF1 in 'C'. It takes about 4 hours to read and write registers. Less is you skimp on flexibilty. I can't anything about how easy you will find implementing DF1 in Visual Basic.

If you only read then you can't hurt anything in the PLC.

To reiterate what Steve said, check with the controls people before you go about implementing this.

Yes, there is a serial port on the SLC, which can be used to read the PLC.

It may also be the way the controls guys get online to do troubleshooting. If they have to unplug your app to fix something, you may loose data. Not good. If they can't unplug your app, they can't fix the problem. Not good.

Allen Bradley has published their DF1 protocol, so, as Peter says, you use that info to build your data packets.

But it may be that there's a SCADA program running somewhere that is already capable of collecting data, and might need just a few adjustments to get you what you want.

The world doesn't need another IT/Controls turf war.

hello all, i'm newly registered.

i have for several years used .vbx, then .ocx controls
from automated solutions for df1/serial communications in vb/c++.

their products are effective, easy to implement, free of runtimes,
and reasonably priced.

they allow "poor man's" hmi's and scada applications to be
easily developed.

hope this helps.

If you are using an SLC-5/04 and are connected via DH+, you could connect using RSLinx Professional and read data from any PLC on DH+ network directly to an MS Excel spreadsheet. Here is a brief example:

Establishing a DDE link to Microsoft Excel

From RSLinx Professional:
1. Click the File menu/Open Project, then click the New button.
Type in a project name, such as TEST and click OK.

2. A topic is a pointer to a PLC, much like how your telephone number “points” to your house.
· Right-click a station and select “Configure New DDE Topic.”
· This will create a NEW topic – to only see or edit an existing topic, use the menu item called DDE/Topic Configuration …
· Click the done button.

Once a DDE topic is configured, you are ready to establish a DDE Hot Link to Microsoft Excel.

1. If RSLinx is not already running, start it now.
2. Select Edit/Copy DDE Link to Clipboard.
· A Copy Link to Clipboard box will appear.
3. The Data Table Address you wish to copy goes in the first block.
i.e. T4:0.ACC
4. In the Block Size box enter the number of words or bits to move.
5. Enter a value in the Columns per Row box.
6. Pick the topic you have configured, TEST, which is displayed in the Select a Topic box.
7. Click OK. All of the information required to establish a Hot Link to Excel is now residing in the Windows clipboard.
8. Start-up Microsoft Excel, but DO NOT CLOSE RSLinx.
9. Place the cell pointer in the cell that you would like the Hot Link to be put in.
10. Select Past Special, source of Paste Link and click on OK. The Hot Link will be pasted into the cell and data from the PLC will appear.

Kim