DH+ Question

Well,

I thought I had my little DH+ network straitend out I added a DHRIo card and was learing how to message through it and even set up an ethernet card to bridge through all was good.

On the down side I was having to use 82 ohm resistors to make it work and had an occasional node drop off but was not a big deal since messaging was not critical.

Then this week I added a PVPlus with the DH+ adapter and the whole thing died.

Step 1 put correct resistors in, PV works but DHRIO dies

Step 2 Take one resistor out PV dies DHRIO lives

Step 3 put resistor in (150 ohm) pull plug on DHRio and all other processors show up rock solid

So Something is up with the DHRio I suspect all along it has been marginal and causing problems but masked by my backward engineering.

Whats up with it or do I have it configured wrong? or what

Thanks Clint

I have read everthing on the AB site and searched here and the knowledgebase and although picked up some great info have not fixed this one.

Anybody

Did you try changing the network speed? You can also see the packet status in RSLinx. I can't remember but I think you can change some settings for packet timeouts or refresh rates. Just a thought.

Almost sounds as though the DHRIO has a high resistance on its connection pulling the lines off balance try metering the ohm values on the two transmit and recieve lines before and after you plug in the DHRIO also how many other nodes are on this line and what is the distance to the dhrio

Carefully inspect all of your cables, it doesn't take much to create havoc with comms when something is amiss. Many moons ago I found someone had hung a bucket on the blue hose up by the ceiling to catch a drip and that threw everything crazy.

Make sure that your DH+ network is installed as per Rockwell recommendations.


I have experienced in the past that someone wanted to place a new node on the network. As it was later discovered, they had just put a new spur on the network. "Spur"? DH+ network is supposed to be sequential. Once that was corrected, the network worked fine.

Thanks for the replies,

There is 4 504's, one plain PV, one PKTXD, and one KTX card and now a PV Plus with the add on comm card, which work good without the DHRIO with the resistors at 150 Ohms and all speeds set to 57K.

Node numbers are:

2 514
3 Channel A DHRIO/b
4 514
5 KTX
6 524
7 Channel B DHRIO/b
8 Was a KTX but computer died and new Motherboard was without
an ISA slot now pulls tags off of a topic on KTX 5

10 PV Plus 1000 with DH +

22 PKTX running wonderware using a topic on linx to pull out of
a 504 (23)

23 514

Although the cables (blue Hose) dont run in a strait line (they zig zag) they all are hooked up one after another.

Form one end to the other is 1000 feet at best and for 90 % of the wire it is in a pipe by itself.

I also have had it on the end of the line and in between nodes

Interesting about the bucket though becouse in two places the cable runs through electrical panels and although they only are control panels (both large) they do kinda loop around and in both are hooked up to a 514

perhaps it's just the card I don't like to give up and blame a pretty rugged piece of equipment though and I don't have a replacement to verify with either.

Clint

Two questions: Do either of the control panels contain variable frequency drives? Is the conduit for the blue hose grounded?


I once had a situation where a SLC504 would pull the DH+ network down when connected. Found out that I could remove the SLC chassis from the control panel and set it on top of the panel and everything worked fine. One of the analog outputs from the SLC ran through a short section of ungrounded conduit to a VFD that was mounted on the wall next to the control panel. The analog cabling was shielded twisted pair with the shield grounded in the control panel. Long story short, grounding the conduit fixed the problem. That's been about 10 years ago and the DH+ is still working fine.

CJones said:

Thanks for the replies,

There is 4 504's, one plain PV, one PKTXD, and one KTX card and now a PV Plus with the add on comm card, which work good without the DHRIO with the resistors at 150 Ohms and all speeds set to 57K.

Node numbers are:

2 514
3 Channel A DHRIO/b
4 514
5 KTX
6 524
7 Channel B DHRIO/b
8 Was a KTX but computer died and new Motherboard was without
an ISA slot now pulls tags off of a topic on KTX 5

10 PV Plus 1000 with DH +

22 PKTX running wonderware using a topic on linx to pull out of
a 504 (23)

23 514


Clint

Click to expand...

I read the above as 10 nodes all on the DH+ networks

You show you have two networks
3 Channel A DHRIO/b
7 Channel B DHRIO/b

Which of the other 8 nodes are on which network A and B. ?
How many terminateing resistors are on each network A and B. ?
Are these terminating resistors only at the ends of each network A and B. ?

Is the bare screen wire of the blue hose sleeved at your terminations so there is no risk of a loose strand touching either the white or blue wires termination. ?

Nodes 2,4,6,23 show as 514 or 524 i assume this is a typo and should be SLC 504

I am the first one to say that DH+ should be installed per the instruction book which says that there are two acceptable topologies. One is trunkline-dropline and the other is sequential. The 150 ohms goes at each end for slow (57) and 82 for fast (130).

Having said that, I have connected up 15 to 20 stations in a complete rats nest in the development lab, ignoring every conceivable rule, and it still works fine even without resistors. I have only seen it get in trouble one time and that was due to one too many resistors.

So this prompts me to suggest that you try to do one or the other scheme, and start with no resistors and test as you go, trying to get to one of the textbook schemes.

As stated above, pay very close attention to the connections. I often tin the last quarter inch of the individual blue hose strands to make the connections cleaner when I put four or five in one connector (in the lab). And the heat shrink tubing on the ground conductor is an excellect idea because it helps to prevent it from grounding out the resistor which could happen with some careless movement of the wiring.

Of course, I would never suggest that the rats nest method be used in a real installation.

In the case of RIO, I never had that many tied together for it to become a problem. If I remember correctly, RIO can go to 230 KB for the fast situation (82 ohms), but you have to have the proper ASB's. Early ones could not go to 230.

Good hunting,

Bob A.

If you have an oscilloscope for troubleshooting, there are a couple of posts that include example waveforms of good DH+ installations in this old thread:

http://plctalk.net/qanda/showthread.php?t=32919

What speed are your DHRIO channels?

Node numbers are:

2 514
3 Channel A DHRIO/b
4 514
5 KTX
6 524
7 Channel B DHRIO/b
8 Was a KTX but computer died and new Motherboard was without
an ISA slot now pulls tags off of a topic on KTX 5

10 PV Plus 1000 with DH +

22 PKTX running wonderware using a topic on linx to pull out of
a 504 (23)

23 514
[\Quote]

Do you have both channels of the DHRIO connected to the same DH+ network? If so, why?

Click to expand...