I am stuck with antiquated equipment and no money. How do I go about connecting my PLC5 to my SLC's? I am using a scanner and DCM's to allow the SLC's to communicate but I haven't found the right set up to talk to the PLC.

Ok, I am going to need a little more info. What are the model/series/revs on your PLC5's and SLC's. From your subject line, it looks like you have SLC5/04's. If that is correct then you should have no problem communicating with your PLC5's via DH+. In fact I would argue that if you are dealing with 5/04's then you took the hard way with the DCM's. I might change my mind if I knew more about your application, but I really dont like RIO for PLC to PLC communication. DH+ will allow the PLC's to talk to each other and a programmer/SCADA system to access them also. Get me some more info on your systems and I think we can work out a solution.

Russell

Russell

Sorry, I should have been more specific. First I am not an engineer just a maintenance flunky. My company does not have a controls engineer and I have to do this in my 'spare time' between breakdowns. I have upgraded all the SLC's to 5/04's so that I could DH+ them to a PV 550 or 600. The PLC in question is a 5/15. I played with DH+ messaging a year or so ago and could get valid communication, but not consistent or dependable, I assume it has to do with scan times. The 5/15 is in a 16 slot chassis with RIO to an ASB in another 16 slot chassis with one space available. This runs the casting press. The 3 SLC's control periferal equipment, one of them has a scanner with RIO to two robots. Due to changes in products I need more communication than the 1/2 dozen hardwired I/O that I have. I would also like to set up a one touch recipe from the PV to all processors.

Thanks,

Eric

Eric,

First, dont get stuck on the engineer/tech/whatever thing. Most of the guys I deal with day to day are not engineers. Many of the best people I have worked with have not been engineers. PLC's are all about experience and having the right person looking over your shoulder when you need it - and knowing when you need it. You are way ahead of most people that take classes in PLC's becuase you are actually getting a chance to use them.

Now to your problem. DH+ is not about scan time in the PLC5. There is a separate processor that handles those communications. To communicate, you need to use a MSG statement and it operates asynchonously to the ladder scan. In other words it gets started by the rung that enables it, but finishes on its own schedule and is not dependent upon the ladder or the order of your program. You should be able to do this, but the MSG statements need to be set up right. Keep in mind that any very fast or very important signals should probably still be hardwired PLC to PLC. I would not use the MSG statment to look at a Push button on one system and operate a valve on another for instance. It would be great for transferring your recipe information for example.

Here are a few suggestions. First I am assuming that you did try the MSG statement.

Put all your MSG reads and writes in the PLC5. Since it does have a separate processor, it seems to handle these communications better.
Set up a heartbeat in each of your processors. You can just use a bit from the second of the system clock if you want.
Check that heartbeat in each of your processors using some timers. If you dont see the heartbeat change from the remote PLC then alarm and the data is considered bad.
Set up separate data tables in each PLC for your send receive data.
Check the error bits and have logic to respond (check the manual to see examples)
Use your message on a timed interval. Each message gets entered into a queue and it will overflow and crap out if you continuously slam it.

OK I have to run, but take this to start with and just get on running - say the recipe stuff. Of course let me know if you have further questions.

Russell

Russell,

Thanks for the info. I had been putting the MSG instructions in the SLC and I was probably setting my interval timers too short. Hopefully I will be able to get back to that project within the next few weeks. Right now I have to automate a trimpress with a robot to load it and devise some way to unload the parts to the operator. All without spending any money. I am still interested in using the RIO for discrete I/O without having to run more conduit. Also becaause when they break/melt things it is much easier to replace a blue hose than a pipe with 40+ wires in it.

For the recipe it would be so much simpler if the PV was capable of addressing multiple nodes on one tag.

Eric

Eric,

Most of the times I deal with panelviews, the stuff is pretty simple. Addressing multiple nodes with one tag would pose some issues with tag addressing that would not only be confusing but difficult to handle on the manufacturers side. However, if you wanted to I think you could setup tags for each of your processors and handle copying data to each group of tags with scripting. I think it makes much more sense to do that at the PLC level. Also, do you really need all that recipe info at each PLC? My understanding is that you have a PLC5 that kind of works like the master PLC and the SLC's operate various support equipment around it. You really just need to pass the info pertinent to the systems being controlled. Another option (I know there is the money issue) is to upgrade your PLC5 to a processor that could handle the programs the SLC's are running. If the subsystems are completely dependent on the PLC5 system to be productive (ie, if it's down they cant do anything) then there is no reason a single processor couldn’t handle it all. If they are independent systems that can operate without the process the PLC5 is controlling then they should remain independent. PLC5's are really cheap on EBay. You might be able to upgrade to something that could handle SLC I/O as extra racks and eliminate some of your pain and suffering. For example there is a 5/40 right now that is less than $300. It would take some time to port the SLC stuff over, but it is an option.

Russell