SLC 5/04 DH+ and wireless radio

I have an existing 10 SLC 5/04 connected via DH+ protocol. I want to put a wireless radio using prosoft technology as a back up to DH+ system.My client needs a back up communication system due to the failure of DH+, so i recommend them to put a wireless radio as a back up without touching their existing network and replacing their existing SLC processor, my question is that possible to have a different protocol at the same time in a network? IF the DH+ fails the wireless radio will act as a back-up, do i need to modify the existing program? Can you give us a sample ladder logic program on how to address this problem? Your immediate response would be highly appreciated.

DH+ failure? Don't hear that happen to often. Sounds like you have bad media or a configuration issue. but if you want to go with back up wireless there are many solutions...keeping with your prosoft idea I would wait for this product to come out
http://www.radiolinx.com/content/view/full/8511
this looks like the way to go.
although the are many other options in the wireless world.
as far as the ladder goes it would just be sending messages. I'm not sure what processes your running and how time critical they are.

My network topology has matured over the years ...

First it was totally PLC5's on DH+. When ethernet started appearing, we installed a few of the PLC5/E processors. Then of course, the ControlLogix - once again on ethernet.

Then the inevitable happened - the process engineers said that the ethernet network was too unreliable and needed a secondary communications path. Well guess what! DH+ was available. So code was developed for primary communications being ethernet and secondary being DH+.

Now we have radio ethernet, wired ethernet, controlnet, DH+, Modbus. I'm sure that we will be maturing further in the future, but I am sure with our migration plans, we can support it.

So back to the topic at hand - yes, you should be able to have a redundant network. Of course, man can do anything given enough time and money. So, if your customer is willing to put up the time and money, it should be possible.

But the question still needs to be answered - why do they think that DH+ is not robust and needs a secondary network? DH+ if installed correctly should be bullet proof.

PLC GURU said:

DH+ failure? Don't hear that happen to often. Sounds like you have bad media or a configuration issue. but if you want to go with back up wireless there are many solutions...keeping with your prosoft idea I would wait for this product to come out
http://www.radiolinx.com/content/view/full/8511
this looks like the way to go.
although the are many other options in the wireless world.
as far as the ladder goes it would just be sending messages. I'm not sure what processes your running and how time critical they are.

Click to expand...

Thanks buddy for the information, the application is this we have an existing slc 5/04 stationary as master and connected by another 9 carrier slc 5/04 via DH+ and it is installed in monorail and this is moving so they are connected by brush contact and this contact act as a DH+, sometimes the contact fails and DH+ as well,this is an automotive application and this application is critical they have a downtime everyday so they want to eliminate this problem using the wireless radio as a secondary back-up. If this is possible would there be any collision of data? Because the data or message will send at the same time in dH+ and wireless radio, How can i program or configure on which is primary or secondary back-up? This is new to me and this is my first time to use wireless radio in a project, thank for your reply i know you can give me more tips and recommendation on how to do it. again thanks for the support

I have not done simultaneous communications over the two networks. I basically do one or the other depending on a handshaking timer. If the primary network takes too long or errors, then switch to the secondary (for a minimum duration + an established connection for a duration of the primary network).


It is rather interesting that you use DH+ on a monorail connected by brushes. I would tend to think that there would be a high failure rate in the communications. How often do they clean the track and replace the brushes?

Anyway - if the wireless proves to be robust enough, I would use that as the primary or even the only communications path.

Ahhh, brush contact, that explains it. I dont know your exact situation. but...You'll just send messages similar to how you do it now on DH+, except through the serial port (DF1) on the SLC. The messages shouldn't collide because (if you use the wireless radios above) that protocal will handle all of that. there are a few options here. 1-Once you receive the messages you may want to compare them to make sure they are both saying the same data. if they are great, if not, either fault or give more weight to the data you beleive is more accurate. OR 2-run the DH+ until it faults then use the data from the radios until the DH+ recovers.

PLC GURU said:

Ahhh, brush contact, that explains it. I dont know your exact situation. but...You'll just send messages similar to how you do it now on DH+, except through the serial port (DF1) on the SLC. The messages shouldn't collide because (if you use the wireless radios above) that protocal will handle all of that. there are a few options here. 1-Once you receive the messages you may want to compare them to make sure they are both saying the same data. if they are great, if not, either fault or give more weight to the data you beleive is more accurate. OR 2-run the DH+ until it faults then use the data from the radios until the DH+ recovers.

Click to expand...

Thanks for the reply oakley and plcguru, i am sorry for the late response due to busy schedules, may i request if possible to give me a simple ladder program on how to do the primary and secondary program ( Wireless and DH+ protocol ) by using msg program. you can email your ladder in [email protected] again thanks for the support.