K
Kevin
- Jan 1, 1970
- 0
I want to build a RS485 network using Cat 5 cable. But since the RS485
specs don't specify connector types I'm at a loss to figure out what I
should use with (easily obtained) Cat5 cable.
Some of the remote nodes attach to equipment that is on wheels (ease
of moving for cleaning, maintainance etc). So I'm thinking that the
cables and connectors may get damaged over time. I would like to use
cables and connectors that are cheap and easily replaceable when
damaged. (Yes, I know the best thing is to ensure that they don't get
damaged in the 1st place, but this is the real world I'm talking
about).
This is half duplex RS485 communication, so it only requires 2 diff.
signal wires and ground. (A total of 3 wires).
I don't want to use a RJ45 connector on the Cat5 cable, as somebody
might think it's an Ethernet network cable and plug it into a laptop
or something.
It occurred to me that RJ11 cable has 4 wires, and might be the
solution to my problem.
What I was thinking of is to run Cat5 as close to each machine as
possible and connect it to a plain old surface mount modular RJ11
telephone box (you know, like what your phone cord plugs into). Then I
could use a standard RJ11 telephone cable (like what connects your
modem to the phone line) to hook the machine up to the network. (The
machine would also have a modular RJ11 telephone box which would be
connected to the RS485 transceiver of the electronics that I'll
design).
This might be more easily understood by this diagram:
Cat5 Cheap Phone Cable Inside Machine
---------[Phone Box]====================[Phone Box]--------------
Cat5 here?
The link cable (phone cable with RJ11 ends) and connectors (RJ11 phone
boxes) are cheap and easily obtained and replaceable.
Now I know that this will probably mess up the differential signal a
bit, since the RJ11 phone cable is not twisted pair. But say the phone
cable is less than 10 feet - will it make a difference?
Questions:
1. Is this workable? If not why? (Communication will be done at
9600bps).
2. What about if I use a slew-limited RS485 driver on all nodes to
help ensure signal quality (minimise reflections etc). Will I be able
to do this RJ11 thing then?
3. Are there any other cheap connectors and cabling that I can use for
Cat5 to run it directly to each machine? What type of connector do you
guys use when you do RS485 networks and how do you handle the physical
wiring arrangement? (Digikey #s appreciated if possible).
Thanks for any advice/suggestions.
specs don't specify connector types I'm at a loss to figure out what I
should use with (easily obtained) Cat5 cable.
Some of the remote nodes attach to equipment that is on wheels (ease
of moving for cleaning, maintainance etc). So I'm thinking that the
cables and connectors may get damaged over time. I would like to use
cables and connectors that are cheap and easily replaceable when
damaged. (Yes, I know the best thing is to ensure that they don't get
damaged in the 1st place, but this is the real world I'm talking
about).
This is half duplex RS485 communication, so it only requires 2 diff.
signal wires and ground. (A total of 3 wires).
I don't want to use a RJ45 connector on the Cat5 cable, as somebody
might think it's an Ethernet network cable and plug it into a laptop
or something.
It occurred to me that RJ11 cable has 4 wires, and might be the
solution to my problem.
What I was thinking of is to run Cat5 as close to each machine as
possible and connect it to a plain old surface mount modular RJ11
telephone box (you know, like what your phone cord plugs into). Then I
could use a standard RJ11 telephone cable (like what connects your
modem to the phone line) to hook the machine up to the network. (The
machine would also have a modular RJ11 telephone box which would be
connected to the RS485 transceiver of the electronics that I'll
design).
This might be more easily understood by this diagram:
Cat5 Cheap Phone Cable Inside Machine
---------[Phone Box]====================[Phone Box]--------------
Cat5 here?
The link cable (phone cable with RJ11 ends) and connectors (RJ11 phone
boxes) are cheap and easily obtained and replaceable.
Now I know that this will probably mess up the differential signal a
bit, since the RJ11 phone cable is not twisted pair. But say the phone
cable is less than 10 feet - will it make a difference?
Questions:
1. Is this workable? If not why? (Communication will be done at
9600bps).
2. What about if I use a slew-limited RS485 driver on all nodes to
help ensure signal quality (minimise reflections etc). Will I be able
to do this RJ11 thing then?
3. Are there any other cheap connectors and cabling that I can use for
Cat5 to run it directly to each machine? What type of connector do you
guys use when you do RS485 networks and how do you handle the physical
wiring arrangement? (Digikey #s appreciated if possible).
Thanks for any advice/suggestions.