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AXLINK OVER CAT 5

ClingpeachClingpeach Posts: 156
in AMX Technical Discussion
Is this doable. Or not a good idea? Its for the new AMX Thermostats?

Comments

  • HARMAN_icraigieHARMAN_icraigie Posts: 660
    Clingpeach wrote: »
    Is this doable. Or not a good idea? Its for the new AMX Thermostats?

    No problem on the data across one of the pairs - issue is power.
  • ryanwwryanww Posts: 196
    I used cat5 on one system I have because it was cost effective for them.. What I did is used the Orange pair for the AXP and AXM and then twisted the blue, green and brown wire and used that for positive 12v and the blue/wht, brn/wht and and green/wht for the ground. As long as you dont go over a couple amps, your fine. I wouldn't use it with anything over 4 amps.
  • ericmedleyericmedley Posts: 4,177
    ryanww wrote: »
    I used cat5 on one system I have because it was cost effective for them.. What I did is used the Orange pair for the AXP and AXM and then twisted the blue, green and brown wire and used that for positive 12v and the blue/wht, brn/wht and and green/wht for the ground. As long as you dont go over a couple amps, your fine. I wouldn't use it with anything over 4 amps.

    The other issue is the voltage drop over the cable. You really cannot go very far. The official legth is something like 30 feet. I've inherited a system that was done in all CAT5. I'd love to slap the person who did it. They used some of the same run for IR, RS232 and AxLink. There is one run that has all this and power too. They all share a ground wire.

    My advice is avoid using it if possible.
  • ClingpeachClingpeach Posts: 156
    Thanks guys. Yes I see the issues which I dont want. Yet ANOTHER wire to be run in the house. Why this uses AXLINK I have no idea. What was the thinking behind this??
  • yuriyuri Posts: 861
    Clingpeach wrote: »
    Thanks guys. Yes I see the issues which I dont want. Yet ANOTHER wire to be run in the house. Why this uses AXLINK I have no idea. What was the thinking behind this??

    What does it matter?

    a) you use Cat 5
    b) you use certified AXLink cable

    ?
  • ClingpeachClingpeach Posts: 156
    It matters because in trying to future wire a house you run tons of cat 5/5e or cat 6 cable. After NetLinx when was the last time you needed axlink wire
  • ericmedleyericmedley Posts: 4,177
    Clingpeach wrote: »
    It matters because in trying to future wire a house you run tons of cat 5/5e or cat 6 cable. After NetLinx when was the last time you needed axlink wire


    Well, Lutron uses that wire incidetally. It's the exact same wire.

    Actually, Axlink is a great communication method. To be frank, I wish they'd use it for more things.

    As for CAT5 and CAT6 and why or why not use if for other things...

    It has a lot to do with the physics. single core wire is best used for AC and multi-stranded wire is best for DC. Technically standard networking is DC. But due to the fact that it operates in the MHZ or GHZ range, it tends to act a lot like AC.

    I can tell you that elecrical engineers have migrains over how folks like us misuse wire. When we use the wrong wire for a job, there's no way to guaranty the performance. It's stuff like this that creates some of the flakiness of gear operation.

    I've been in houses where I've seen speaker level over a couple strads of CAT5e. It was meant for network and telephone.

    But, whatever gets the gig done I suppose...
  • ClingpeachClingpeach Posts: 156
    Noted. I will have my installers run the correct cable. Thanks for all your responses.
  • TurnipTruckTurnipTruck Posts: 1,485
    For the data portion of Axlink, capacitance is the issue. For that reason CAT 5 cable is excellent. Since Axlink is mostly used these days for keypads which draw very minimal current, CAT 5 would work fine especially if you combine pairs for power as someone else suggested.

    CAT 5 is not the right cable to use, but if you have to, no worries.
  • HARMAN_icraigieHARMAN_icraigie Posts: 660
    The AMX Power Calculator is your friend - it will even give you maximum run lengths of power on different wire gauges based on the load

    http://www.amx.com/techsupport/techNote.asp?id=146
  • KennyKenny Posts: 209
    I think the real problem with Cat5 is the actual capacitance of the cable. Axlink likes about 15pf per foot.
    This isn't an issude for short runs but it coulf really cause major issues on long runs.
    Your digital 1's and 0's should be very square but with the wrong capacitance it could turn into more of an AC wave.
    Professionally speaking I would use the proper cable.
  • TurnipTruckTurnipTruck Posts: 1,485
    Kenny wrote: »
    I think the real problem with Cat5 is the actual capacitance of the cable. Axlink likes about 15pf per foot.

    This is exactly why Cat5 makes a good Axlink cable. Cat5 is a low-capacitance cable.

    Axlinx (or any other digital data circuit) is not looking for a specific cpacitance. The goal is to minimize the capacitance by using the lowest capacitance interconnects possible.

    The effect of capacitance on data is cumulative with total cable length in the circuit. Therefore, with ten 100-foot home-runs to an Axlink bus strip, the total capacitance would be that of 1000 feet of wire.

    With 15pF per foot cable, I beleive the Axlink maximum length spec is 3500 feet. Therefore with wire of twice the capacitance, you would cut the maximum allowable length in half.
  • DHawthorneDHawthorne Posts: 4,584
    An alternative is use CAT 5 for the data, and power it locally ... you only need to make sure the ground is common in that case. But that can get awkward too, and it's more than a pain to troubleshoot when the power is all over the place like that.

    If you can run wire, I would, in this case. I generally use Lutron keypad wire for such jobs, since I always have tons of it on hand. I'm also to the point where I will run two Cat 5's and either a 4/18 shielded cable or 7/18 to any control location, whether I think I will need it or not.
  • TurnipTruckTurnipTruck Posts: 1,485
    I use West Penn 77350 for my Axlink runs.
  • KennyKenny Posts: 209
    Per the AMX Tech notes
    http://www.amx.com/techsupport/techNote.asp?id=464

    Liberty Wire and Cable, www.libertycable.com, and Comprehensive Video, www.comprehensivevideo.com,both sell cables specifically designed for use with a network like AXlink. Here are some features of these special-purpose cables:

    one 22 AWG pair of separately-shielded, low-capacitance (12.5pF/ft) conductors for data. Low capacitance allows the data to travel further without degradation. Shielding reduces induction of noise from other sources, as well as emission of noise into susceptible nearby circuits.
    one 18 AWG pair of conductors for power. Relatively high capacitance (35-50 pF/ft) serves to filter noise from the power source. The larger wire means reduced resistance, which allows for greater distances.
  • mushmush Posts: 287
    As Axlink is essentially RS485 you can quite safely run it over CAT5/6 cable, shielded cable is best.
    As previously stated the real problem is power which you would also have with ICSNET.
    So run shielded CAT5/6 cable and you have future proofed your install.
    Read this if you want in depth info.
    http://www.maxim-ic.com/appnotes.cfm/an_pk/763
  • bobbob Posts: 296
    DHawthorne wrote: »
    to the point where I will run two Cat 5's and either a 4/18 shielded cable or 7/18 to any control location, whether I think I will need it or not.
    Dave, what wire is this 4/18 and 7/18? Thanks!
  • DHawthorneDHawthorne Posts: 4,584
    bob wrote: »
    Dave, what wire is this 4/18 and 7/18? Thanks!

    <number of conductors>/<wire gauge>, so that's 4-conductor, 18 gauge and 7-conductor, 18 gauge, respectively.
  • bobbob Posts: 296
    Thanks! May I ask what is the thinking behind 4 or 7 wires?
  • DHawthorneDHawthorne Posts: 4,584
    Axlink and other RS-485 busses require 4 conductors, so that is the minimum. I run the 7-conductor in case anything gets added ... like RS-232 control, IR, or even just the need to double up conductors due to voltage drops and current draw. Neither does it matter if the device at the location doesn't rquire any of this; I have often had a customer come to me a year after an installation and said, "can I add <whatever> to my system in that room?"; because I had extra wiring in place in the general area, it became much easier to say "yes."
  • bobbob Posts: 296
    Dave, but having cat5/cat6 into that remote area, you just put an NI-700 or NI-900 there and connect it to the master through ethernet and use its RS2323/IR/IO ports. It's probably more expensive though I think a better solution and more flexible solution. Possible that you will need a switch/hub there, it is added cost... Hmm, probably you are right by just pulling an extra cable.
  • [Deleted User][Deleted User] Posts: 0
    Tech note 907

    A tech note was just released on this subject.

    http://www.amx.com/techsupport/techNote.asp?id=907

    The referenced PDF linked to the tech note pretty much spells out best practices for using CATx for Axlink cable runs.
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