CAT5 wiring question

[Max-Paul]

LOR offers a Network Repeater  that "Has one RJ45 jack on the front and two RJ45 jacks on the back to allow the network to ‘Y’ "

Thanks Ken, as I started to read from the last post I read yesterday I came to the same thought. If only need to split to two cables. Gents Ken beat me to it and I agree with Ken. Best way to split is to use the repeater.

[Max-Paul]

Thanks klb you explained good reasons to stay away from stubs. I will also point out that LOR are now releasing devices that can run at 115Kbs I think it is. Verses the current 9.6Kbs. Quite a jump in speed. And with this there is no free lunch. There is a trade off. This trade off is that the signal is more sensitive to stray noise and the actual wiring of the network. I am sure many of you know that Cat5 had a 300Mhz limit and Cat5e had I think 500 Mhz limit. Then along came Cat 6 with 1Ghz limit I think it is. The Mhz translate into Mbs. As the frequency went up the quality of the cable has to go up. So, even though the frequency compatiblity of Cat5 is still many times greater than 115Kbs. The connections, location of the wire in relationship to noise producing items, and kinks in the cable can kill the signal.

 

Now I am going to step out from klb's thinking and say that if you are having major problems with lights blinking when they should not or coming on and stay on till the end of that song. Then a termination resistor might be needed in the last controller. I will concede that you need to really check each of your cat5 cables and the sockets on each board. We have loose sockets with back solder joints on the back of the board. WE have the little wire contacts in the sockets that get smashed down and need to be lifted carefully. Then there are the bad terminations in the plugs or the broken wires in the cable (solid wire only will flex so many times before it breaks).

 

Ok, sorry got a little carried away.

Edited January 20, 2014 by Max-Paul

[-klb-]

The sound pipe example does continue to work. An open pipe end does reflect air waves, or else a flute would not play a note. If you put a suitable muffler on the end of a flute, or our sound pipe, you would no longer get the reflection off the end. The flute would not play, and someone listening just before the end of the pipe would hear a cleaner signal.

It certainly can't hurt to try a terminator if you are having lost command issues. We have a couple of experienced users who have cleared up their issues. But we have also had several who reported only partial improvement with a terminator, and tracking down a connection fault actually fixed it. And quite a number who have found bad jacks, or bad from the factory cables.

Also, default LOR is 56Kbps, super speed is 500kbps. So quite a difference, but still roughly three orders of magnitude slower than the 350mhz that most cat 5 and higher cable is actually tested to. Gigabit copper actually only runs 250Mbps per pair, and uses all 4 pairs. It allows for both ends to talk on all pairs at the same time, and still sort out what the far end is saying, opposed to what is cable reflections of itself talking.

But yes, the 10 fold increase does make all reflections, even from just the connectors that much more significant.

[Bizywk]

You're talking about the harmonic response of a circuit.  That clears it up for me guys.  Thank-you all. 

 

We'ill keep to the preferred typology in our design, but will also keep my handy dandy Y cable available for emergency operation.    You're exactly right, I used it to feed only one LOR controller off the main line of the higher speed LOR Network (USB-RS485-HS) after I had the output data port on one controller fail.  The two controllers were mounted side by side and the stub was less than 24".   

[TheJackal]

It is not simply a copper splitter, it has active electronics to duplicate the signal to a new separate network.

This I understand. Much of what was said above went over my head. But, that's ok.

 

Using long cable to run from one side to the other is cheaper. But, I'm keeping my options open.

Edited January 20, 2014 by TheJackal

[Tim Fischer]

Great thread guys, nice job!   This helps to answer a few questions I had but haven't asked yet.

 

This last season, I tried two experiments.  The first was to create a homebuilt passive "Y" cable for use on our LOR network made by simply taking two factory CAT-5 cables, cutting them in the middle and soldering the wires of three of them together - matching the wire's color codes.  This gave me a simple One-in-Two-Out  Y cable that helped me out of a jam.  It was dark with visitors out front and the output daisy chain port of one of my controllers suddenly decided to not work.   The cable worked perfectly until I could get a repair done to the controller.   

 

The second experiment was to add a simple 5 port NetGear HUB (NOT a managed switch) to our RGB (E1.31) network which allowed me to run one trunk line to feed 3 SansDevices controllers on the other end.  This worked perfectly too. 

 

I wasn't sure if we were just lucky or whether this was a viable configuration option.

Both your examples are perfectly viable.

The first is viable because you're keeping one leg of the "Y" very short - presumably just long enough to connect to the broken controller.  In reality, the two jacks on the LOR board are wired just like this.  The RS485 spec disallows splitting, except for the case like this  where, at a device, your doing a split with one very short leg.

The second is viable because you're using an ethernet switch to split an ethernet signal - exactly what it was designed to do.

 

-Tim

[nam1956]

Thanks, but Nam are my initials not a reference to the war. A lot of people make that mistake, I do share your thoughts for our brave men and women that do serve our country. 

[Steven]

So there will be 2 controllers on the left and 3 to the right. The house (measured the eaves) is 50 ft wide. The Director will be inside the garage (left or right, I'm not sure). If I could split the CAT at the garage (1 into 2...not 3 like in the picture), it would make things easier.

 

A proper RS485 network cannot have any "Y's" in it. That is, it must be a single line from the first node to the last node.

 

However, the computer (with the USB-485) is one of the nodes. If you have your computer in the middle of the network, that in still in spec. I run my show this way, with the computer in the garage in the middle, and the network goes east and west from the center point. I found that in my situation, it works better if I put a terminator on each end.

[TheJackal]

it works better if I put a terminator on each end.

This part I don't understand.

[Steven]

This part I don't understand.

 

See this post.

[Max-Paul]

Ok, a bit technical but here it goes.

 

When the adapter at the computer sends out a signal if there is any imbalance in the cable/circuit there can be reflections of the signal. These reflections of the signal can mess with the controllers getting a signal that is not garbled by a reflected signal. So the 120 ohm resistor is a load that adsorbs any reflections before they become a reflection. If you ever was a CBer or a Ham radio operator, you would understand that a untuned antenna would have a high SWR. And the R in SWR stands for reflections. So, we want a tuned circuit per say.

[Steven]

And the R in SWR stands for reflections.

It actually stands for "Ratio", but it's true that the SWR is an (indirect) measure of reflections. An SWR of 1.0 means no reflections, and an infinite SWR means 100% reflection.

 

 

[Max-Paul]

Dang getting old it a real pain in the arse. Thanks you are correct and I slipped. A ratio of the strength of the signal going out versus the reflected signal strength. Dang this memory slipage. and I am only 55. And to think I have an advance class ticket, a 2x2.

[Steven]

And to think I have an advance class ticket, a 2x2.

I have a 2x1. Maybe that's it. :-)

[Max-Paul]

Yes just a bit easier to remember Steven.