Using CAT5e for power (RGB LED strips)

[danrogers]

Hi all, I need to power some rgb strips, and I'm thinking of using cat5e because I have loads.

I'm wondering if I should use all 8 cores, this means I could power 2 strips from one run but will the fact that the cable is twisted pairs give me any cross talk between the channels? Or I could use one run of cat5e per strip and double up the twisted pairs.

The length will be around 6 meters max, and the current on each conductor will be around 0.2A

thanks

 

[Mr RB]

Is the PWM being transmitted over the 6 metres of cable? Or is the cable supplying DC to the remote PWM/LED module?

 

[danrogers]

Hi Roman, yes PWM will be transmitted - forgot to mention that?

 

[Mr RB]

That sounds a bit nasty. I'm not sure how much EMI it's going to generate with just the simple foil shield on that cable, and the high current PWM pulses.

I think it would be a good idea to read up on if there will be a noise issue using long cables or unsuitable cables. The LED driver datasheet should have some info on what it can safely drive.

Personally I just wouldn't run multiple high current PWMs over 6 metres of cable. Maybe you can put the LED PWM driver device close to the LED load?

 

[danrogers]

The other option I thought of is to use some 8 core alarm cable, its hard to find spec's but I think its 24AWG so should be OK for about 1A and of course it is not twisted. The driver is a custom made circuit that I have built, based on 74HC795 shift registers and mosfets so it won't be possible to move any closer to the strips unfortunately.

would the twisted pair cable exaggerate EMI issues or should I try some non twisted?

I think the current will actually be only around 0.1A per conductor actually.

 

[kubeek]

Well if you use the pairs as intended, that is each pwm has its own ground coming back throught the same pair, then the EMI will be less then in a non twisted cable.

 

[danrogers]

I thought that but it would require a cable run for each strip (I need common 12v supply and 3 PWM GND's)

I was hoping to run 2 strips from 1 cable - so 6 channels basically?

 

[ChrisP58]

Is the PWM just brightness control for the LEDs? If the frequency is fairly low, (<100Hz) you shouldn't have much problem with cross talk or EMI.

 

[danrogers]

Yes I think the default is 75hz but I can adjust it so hopefully I can keep it Low enough to aviod flickering

What is the general consensus then, twisted pair or standard?

Thanks all