Connectors for a RS485 network

[darrenb]

Hi,

I have to put together a RS485 network on of all things a super maxi called InfoTrack.

The network is to connect together a PLC, an Arduino and a Raspberry Pi using Modbus.  I've got these all talking to each other now I just have to come up with the actual cabling and connectors.

As I haven't been able to google anything off the shelf for this the best I have been able to think of so far is to use a 6 terminal terminal block at each connection point and mount this in a jiffy box.

The six terminals are 1 to 6, 1 and 2 for the RS485 network coming in or if there is no other connection a 120 ohm resistor.  3 and 4 for the A and B for the device at this point (pi, arduino etc) and 5 and 6 for the RS485 network going out or another resistor.

On the other side of the terminal block I'll just wire 1 and 3 together, 2 and 4 together and so on.

For cable I am thinking of using 4 core twisted pair telephone cable.

This should all work but I can't help thinking there must be a better way.  Surely other people have had to create RS485 Modbus networks?

[ledtester]

I think RJ45 (i.e. ethernet) cables are commonly used for RS485. Yeah it's overkill, but then you have future expansion possibilities and you also have a cable run which can be used for lots of other purposes.

You might plan out your conductor assignments so that you can carry both RS485 and 100-baseT ethernet (which only requires 2 twisted pairs) at the same time.

[darrenb]

I just realised that I also have to provide ground and maybe also a shield connector so my idea of using a 6 terminal terminal block won't work.

Looks like I'll have to make up a pcb using either rj45 or rj11 connectors.

[digsys]

I've used several methods over the years - including phoenix 0.15" 6/8W pluggable >> and now using CAT6 shielded PoE pinouts, which I also use for CAN Bus.
In serious "factory" electrical connections though, I always go for fiber > fiber converters

[vk6zgo]

The only RS485 network I've had anything to do with used 9pin "D" connectors.
A  bit clunky, maybe, but they have plenty of spare pins to play with!