Remote switching of relay modules project

Hi

I’m planning a project where I’ll need to switch two relay modules that are 50m from an ardunio

I have two of these:
http://www.ebay.co.uk/itm/12V-1-Channel-Relay-Module-with-Optocoupler-H-L-High-Level-Triger-for-Arduino-UK-/152003483240?hash=item23641d1668:g:EvsAAOxyUrZS4OHT

The arduino is an arduino uno

I was planning to power the modules with their own 12v power source at the two remote destinations and simply run two control cables back to a digital pin on the arduino (see attachment).

Does the ground at the relay boards need to be connected to the ground on the arduino?

Can I use Cat5 for the control cable?

Thanks

1.) Learn how to create clickable links.

2.) The grounds need to be connected.

3.) Why Cat5 cable?

Because it's cheap?

I may use speaker cable.

instead of the long run of lossy wire use a WIFI shield (under $10.00 US) with a directional antenna ($2 to $10 U.S. found on EBay 2.4 gig circuit board antenna) so you can place the UNO at the site of relays.

This is a project I am currently working on. I will be using a Ethernet Shield (on mine) with a mesh network router system to switch a 4 relay setup like yours (controls antenna switch up on remote tower site). A rotor control box (controlled by UNO and same relay setup with remote link software) and radios are connected over that same mesh network for remote control. With the correct antennas on
wifi link you can go as far as 24 miles if you have line of sight without any RF amps.

Hope this helps.

Have a great Day, Clint

Anyone have a suggestion on the best way (protocol) to push a command to the UNO over Ethernet. Currently am using the WebServer# (https://www.arduino.cc/en/Tutorial/WebServer#) to see the status of the relays over Ethernet.