# power over cat5



## stirling (Jan 10, 2007)

Simply put, my question is can I use cat5 patch cord to carry four 50Vdc 3Amp circuits.

More detail. This has nothing to do with networking. I need to drive two stepper motors on a machine where the space to feed the cables is very limited. One option is to use 8 core cable with screen, but it's just a tad too thick. So I hit on the idea of using cat5 which is just the right physical size. By the way it's about 1.5 m or 5ft long. The signal pulses between 0V and 50V at around a maximum frequency of 50KHz.

So anyone know if "she'll take it captain"? - as Scotty would have put it, bless him.


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## crazijoe (Oct 19, 2004)

It may carry the voltage but I would question the current load.

PoE (Power over Ethernet) is very common with VoIP phones and networking equipment using CAT5 ethernet. However it uses 48VDC with only 400ma. Cat5 isn't going to carry 3A.


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## Aus_Karlos (Mar 10, 2007)

3amps is way to much for a 0.2mm copper line its max current rating is 800-1000ma, you will need at least 1mm, the cable that they use it install lights is 1.5mm thick with 3 cables Red,Green/yellow, brown or lightblue. That can hold a max of 10-15amps .. 
Drill a bigger hole is one suggestion.. Or come in through the celling and down a wall


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## johnwill (Sep 26, 2002)

24 gage wire has 2.5 ohms of resistance for 100 feet. For 5 feet, the resistance is 0.125 ohm. The drop for 3A would be minimal, and since the stepper current is not constant, I suspect it would work fine. A bigger concern, at least for me, would be the current capability of the RJ45 connectors. You could also use CAT6 patch cables, they have 23 gage wire, and slightly lower resistance.


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## stirling (Jan 10, 2007)

crazijoe and Aus_Karlos say no, johnwill says yes.

I'm going with johnwill and giving it a go. I'll let you know how I get on.

If the rj45's can't handle it but the conductors can, I'll swap to some other connectors. Foremost is the physical dimensional requirements I have on the cable and the fact that the twist should serve in lieu of a screen to keep down the EMF.

But meanwhile thanks to all for your input.


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## johnwill (Sep 26, 2002)

For a short run, I have no doubt that CAT5, and preferably CAT6 will handle the current, especially being a pulsed waveform. The average current will probably be half or less the actual phase current to the stepper motor. Think about PCB traces that have a much smaller cross sectional area that carry considerably more current. :smile:


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