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Cat5E SC485 Y cable


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Dan

Due to where the Cat5E cable comes out of my house I was wondering if there would be any problem if I was to splice a Y into the cable and send 2 cables in different directions. I just hate to have to run 1 cable to one bank of controllers, turn around and go back past the first to another set of controllers (but I will if I have to).

Please see the attached pic

Thanks

Bill


Attached files 131074=7769-rj45.JPG

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I believe it's been mentioned before that you want to avoid doing this.

Can't remember the exact reason, but I want to say it has something to do with the RS485 protocol.

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bhays wrote:

I think it all depends on which pairs LOR uses. In standard datacomm use, you would need one of these: (actually a pair of them)


If memory serves me correctly LOR uses the 4 center pins - 3,4,5 and 6 on the cable. Communications is on the center pair, pins 4 and 5, and it is used to both transmit and receive. Pins 3 and 6 are used to transmit power for remote devices.

Bill
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Bill,

To answer your question, YES. You can splice these cables and not effect the LOR system. I had to splice to keep from double running long lengths while going across the cannal. And yes, the center 4 pins is what LOR uses. I used the 8 pin connectors for my display in Bricktown but used the center 4 pins only. Didn't have a problem doing it this way and it worked all season (except when I had a bad cable I had to replace). I looked for the same connector bhays showed but no local store had that connector so I had to improvise. I had 14 controllers spread out everywhere that worked just fine.

Just an extra note: you can use the other 4 wires to create a loop of all your controllers to an alarm system so it one gets disconnected, the alarm would sound off.

Hope this helps.

Tom

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Santas Helper wrote:

Just an extra note: you can use the other 4 wires to create a loop of all your controllers to an alarm system so it one gets disconnected, the alarm would sound off.

THAT, is the idea of the year!!!
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bhays wrote:

Santas Helper wrote:
Just an extra note: you can use the other 4 wires to create a loop of all your controllers to an alarm system so it one gets disconnected, the alarm would sound off.

THAT, is the idea of the year!!!

Yes Tom, that is a mighty fine idea:]
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As others said, the center two pins (4 and 5) are used for the signaling. Pins 3 and 6 are used for power, but you really don't need to run power over long distances because it would be too much of a voltage drop anyway. The only LOR devices that require the power pins are the Director Card (which you only use if you don't use a PC), the Wireless Linker, and the new motion detector.

I bought a 200-foot spool of 1-pair twisted pair wire, commonly used as patch wire in phone closets. I'm going to experiment running that to my neighbor's house. The single pair is much thinner than a cat-5 cable, so it should be easier to run over bushes and won't be a visible, although it will have a higher likelyhood of getting damaged.

The reason not to make a 'Y' split is familier to "old boys" of Ethernet technology. When a high-speed signal is sent over a transmission line (like a twisted pair), it will be reflected at any point of discontinuity. To prevent this on the ends of the RS485 line, a terminating resistor should be used. It is impossible to prevent the reflection at a 'Y' connection. See http://www.maxim-ic.com/appnotes.cfm?appnote_number=763&CMP=WP-1 for more information. Of course, you will only have a problem if the RS485 system has enough things "wrong" with it that the reflections overcome the signal. That only happens in extreme situations with long cable runs, etc. The bottom line is go ahead and make the 'Y' connection, but make sure you test everything. If you keep at least one leg of the 'Y' very short, then it will probably be ok.

I'm running audio over the extra pairs (pins 1-2 and 7-8). I built a circuit with small audio transformers (http://www.oselectronics.com/ose_p119.htm) that transform 8 ohms to 500 ohms, which goes over the unused pairs. At the other end I have an identical transformer and an 8-ohm outdoor speaker. I haven't yet tested this over the 100-foot run of cat-5 yet, but I'll let you know.

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If it is true that you can use "Y" connectors than why is it note shown in the LOR set up tutorials? This would make set up so much easer in more way's than one. AI

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