Transmit data through cat5 cable

electronics
software

#1

Im thinking about building a ROV that is controlled through a cat5 cable.
The ROV will be sending video signals through the cable, while the computer is going to send signals that activate motors.
I know there are ip-cameras that sends video through ethernet cables
and I know that a cat5 cable consists of 4 twisted pairs.

So does an ip-camera send signals through 1, 2, 3 or 4 twisted pairs?
That means that controller signals can go through the other pairs.

And how would I code computer inputs into signals and then let the ROV decode them into motor activations? Guidance and links are appreciated


#2

Normal eithernet like Cat5 has a transmit (TX) pair and a receive (RX) pair. The camera’s data is chopped into packets and sent along the cable and those packets are mixed with commands for controlling the motors. So it’s not like those wires are dedicated for a specific function because the data travels back and forth mixed togther in packets.

Just so you know here is the pinout for a Cat5 cable where you can see the TX+ / TX- and RX+ / RX-:
http://pinouts.ru/NetworkCables/Ethernet10BaseTStraightThru_pinout.shtml


#3

Thank you. What about the other 4 wires that are not RX and TX, can motor signals be sent through them?

Also, is there a name for this process of sending/receving data through wires? so I can google it up.
I guess this will require programming skills


#4

The tether on the OpenROV is only two wires which is a special version of eithernet to minimize the wire count and still get long signal propagation at high speeds. The TX/RX pairs are changed from full duplex to half duplex so they can go from 4 wires to 2 wires.

On CAT5 pairs 4&5 are for voice and pairs 7&8 are auxiliary. You could use them for control, but a more elegant solution is to encode motor commands into the data stream rather than have dedicated controls for each motor from the topside.


#5

Alright, are there programmable components that encodes motor commands into datastream ?( i guess there is a built in one in computers)

and components that sort out the signals from ethernet cable to motors?


#6

That’s the primary purpose of the OpenROV’s controller board.

The v2.8 OpenROV Controller Board functions as the electronic interface between your control device and your OpenROV. The Controller Board directly handles the low-level commands to devices such as the sensors, motors, servos, and lights.