Data and power in 1 cable? - Page 1
Forum section: electronics / beginners

author: mortos360
author_rank: Regular Contributor
timestamp: November 30, 2016, 03:16:19 pm
content: I need to make a cable to control my servo motor that is controlled over CAN bus, and I was wondering if I can use only 1 cable that is gonna deliver power and CAN communication?Motor need 48v DC, 24v DC for the break and I think 3 wires for the CAN bus. Question is can I use just 1 shielded cable for everything, or does the CAN communication need to be keept separated from DC power lines?

author: technix
author_rank: Super Contributor
timestamp: November 30, 2016, 03:31:10 pm
content: Quote from: mortos360 on November 30, 2016, 03:16:19 pmYou can run all those signals and power in a single cable, over different conductors within, as long as your communication interface can cope with all those crosstalk, and your cable can handle the current. CAN is fairly robust against crosstalk, so that may not be a big problem. However delivering all those power is a different story.You can put DC-DC converters next to the control circuitry and the break to make then accept 48V power, so only one set of 48V power rail is needed, reducing the conductor requirement to 4.The 48V power requirement is tricky, or I may suggest you try to abuse some USB cables as it is designed to pass power along with a differential pair for high speed signal. USB cables may not have the 50V-rated power conductor you should be expecting, but you can check for newer cable designs that have USB Type-C in mind, and offers thicker and 50V-rated power conductor.

author: tszaboo
author_rank: Super Contributor
timestamp: November 30, 2016, 03:34:31 pm
content: If you have twisted cable, make sure can is twisted. Use separate can gnd and power gnd. Maybe add some ferrite beads to stuff. Otherwise yes, you can. CAN is robust for voltage drops and common mode noise, even differential noise, becuse voltage levels are high. That is why it is in a car. You have a bunch of motors and servos and everything in a car, and they are connected with a single cable assembly.

author: mortos360
author_rank: Regular Contributor
timestamp: November 30, 2016, 03:40:53 pm
content: I need to make my own cable anyway so I can just buy cables that a tick enough and have enough conductors for what I need, I just wasnt sure if I need to keep my CAN on a separate cable.The reason why I want them all in 1 cable is that I will have just 1 connector.. which makes it cleaner looking and easier for handling.The car example.. I wasn't sure if they have some special cables that may have a second shielding inside the cable just for the data lines.Anyway, thanks for the answers!! Ill give it a try.

author: technix
author_rank: Super Contributor
timestamp: November 30, 2016, 04:28:14 pm
content: Quote from: mortos360 on November 30, 2016, 03:40:53 pmJust make sure your CAN pair is twisted, and your power cable is Thick enough to handle the power.

author: tszaboo
author_rank: Super Contributor
timestamp: November 30, 2016, 06:22:21 pm
content: Quote from: mortos360 on November 30, 2016, 03:40:53 pmthe thing we need to keep in mind with cars, is that they are doing everything in their power to keep the costs as low as possible. So no shielding of any kind, whenever possible. They already have some km. of cables in cars as far as I remember.