Remote I/O or DH+ (How to tell the Difference)

We are using alot of PLC5 where i work (Old Papermill) and there are alot of DH+ and Remote I/O comms being used. My question is how could you tell if a (Blue Hose) coming from a PLC 5 60/E is Remote I/O or DH+. The (blue hose) is located in a Remote I/O cabinet but isn't going to the 1771 ASB rack. it goes into a termination box and back out. Is there anyway to do this with out disturbing the system The drawings have been missing for a while and i need to know before install a Panelview.

Thanks for any help you can give
JM

Going off memory I only did a few 5 systems. the ASB can only be RIO. If you pull up the program and look under communications it will show you which port is DH+ and what is RIO.

I should have been a clearier. I know which channel is DH+ and which is RIO, but this cabinet is about 300 yards from the PLC cabinet and there is mulitible termination box for the (blue hose) some of which go up to the ASB and just come in the cabinet and go back out. I am thinking the ones that go in and out are DH+ because i wouldn't see much reason for them to be there if they were RIO.

I was wondering if there was a way to be sure that this was DH+ or Remote I/O electronicly ie... voltage/amps. I havent' had alot of dealings with DH+ so i am not realy sure of the specs.

If the hose passes through a 'termination box' and it's labeled 1770-SC (station connector) it's likely DH+. This is used to provide a drop point for a DH station device - like a PLC. I never saw RIO going through a 1770-SC.

RIO and DH+ are electrically identical; the voltages and waveforms are going to look exactly the same.

It's possible, but not very practical, to use an digital storage oscilloscope to manually decode the packet headers and determine if they are RIO protocol or DH+ protocol. At a higher level, the packet length and order are going to look different, but this method is not well documented.

I agree that if the cable goes in, then out of the junction box where there are RIO racks nearby, then it's probably a DH+ channel.

If the networks were wired by the "book" then with RIO the #1 conductor is blue, with DH plus it would be the clear.
At least that is what I remember.

After doing some more research and asking some (oldtimers) that still work here. i confirmed that it is DH+
Thanks for the help

JM

Mike_RH said:

If the networks were wired by the "book" then with RIO the #1 conductor is blue, with DH plus it would be the clear.
At least that is what I remember.

Click to expand...

I would not use the colour-coding to tell me what the network was.

Back in the "good old days" when I worked on many DH+ and RIO networks, I saw a huge number of connections that were definitely NOT done by the "book". Many of the three-terminal plugs had the "wrong" colour-coded wiring, so it was impossible to tell directly what the network was. In them days many people just hooked it up and got it working, usually involving some swapping around of clear/blue wires... it doesn't follow that the swapping was done at the right end though....

Daba,
Why not work on the assumption that systems are designed / built according to the equipment manufacturers manuals?
I am not saying it will always be the case, but it a better starting point than guessing. No?

Mike_RH said:

Daba,
Why not work on the assumption that systems are designed / built according to the equipment manufacturers manuals?
I am not saying it will always be the case, but it a better starting point than guessing. No?

Click to expand...

Maybe but not much. I worked with DH+ and RIO for a long time before realizing their even was a standard. If it is mission critical then you can't just guess.

The only thing I can think of would be to wait until a shut down and unplug something and see what network drops and then go from there...

Mike_RH said:

Daba,
Why not work on the assumption that systems are designed / built according to the equipment manufacturers manuals?
I am not saying it will always be the case, but it a better starting point than guessing. No?

Click to expand...

I never work on any assumptions regarding DH+/RIO connections. I've even come across mid daisy-chain connections (two blue hoses into one connector) that had the clear wire of one blue hose in the same terminal as the blue wire from the other - and no indications on either blue hose to identify where it is going to/coming from...

As I've said, commissioning engineers find a node that isn't communicating, and swap the clear/blue at that node, regardless of standards, and walk away smiling when it starts working, possibly to do it all again at the next panel.

Jmeadows7676 said:

I should have been a clearier. I know which channel is DH+ and which is RIO, but this cabinet is about 300 yards from the PLC cabinet and there is mulitible termination box for the (blue hose) some of which go up to the ASB and just come in the cabinet and go back out. I am thinking the ones that go in and out are DH+ because i wouldn't see much reason for them to be there if they were RIO.

I was wondering if there was a way to be sure that this was DH+ or Remote I/O electronicly ie... voltage/amps. I havent' had alot of dealings with DH+ so i am not realy sure of the specs.

Click to expand...

Let us be quite clear about this - there is NO electrical difference between DH+ and RIO networks. They both use the same cable system (let's ignore the cable covering colour for now), and the same transceiver chips in the nodes. They both support up to 64 nodes, and both can be "daisy-chained", as you'd expect because the network physical transport layer is identical.

The only thing that makes the networks "different" is the language, or protocol, that the nodes use to communicate with each other.

So what makes the networks "different", is the devices that communicate on them, i.e. how they talk.

As far as I know, there isn't any hardware that uses both DH+ and RIO protocols simultaneously, but there are devices that can use DH+ or RIO by configuration.

As for the cable colour-coding, it was a specification laid down by Allen-Bradley that RIO was 1-clear, 3-blue, and the opposite for DH+ --- or was it the other way round