How many cores do I need to control RGB LED strips

[MikeSharp01]

Just got to pull the last few cables through in the Garden room and I have two lengths of Ceiling wash RGB LED lighting I need to feed. My plan is to run a multi core cable to each of them and have the controller in the systems cupboard. I am not sure of the number of cores I might possibly need as I have yet to choose the LED product. Also as this is a test bed for the main house I may want to change it. Anybody got any experience to share?

Edited September 9, 2017 by MikeSharp01
Punctuation

[Nickfromwales]

Buy them first . Usually 4 cores. 

[Jeremy Harris]

As Nick says, usually four cores, unless the strip has integral controllers (some do).  Worth looking at the current required carefully, as long lengths of strip may need connections both ends.  The super bright LEDs can draw a fair bit of current, often enough for the LEDs at the end of a long (say 4 to 5m length) to look slightly dimmer, due to the voltage drop down the thin tracks on the flexible PCB they are fitted to.  I found that connecting to both ends of a long length of white 5630 LED strip evened out the light from both ends, and reduced the size of the connecting cable needed - in effect you're creating a ring circuit, that shares the current a bit better than just connecting the strip as a radial.

Edited September 9, 2017 by JSHarris

[MikeSharp01]

28 minutes ago, JSHarris said:

The super bright LEDs can draw a fair bit of current

How much is a fair bit these days? Better get the cross section right, was working on 500mA @ 24V = 12W per colour / 1.5A return but could be way out.

[Jeremy Harris]

The 12V 5630 white LED strip I have uses over 2.5 A per metre, but the lower powered RGB strips usually drawa fair bit less than this.

 

The specs vary depending on the LED used and the spacing.  Most strips use 60 LEDs per metre, in groups of three.  The 5050 LEDs are the most common size used in RGB strips, as they are a package that contains three (sometimes four) 3528 chips.  Having three different colour chips in a single package makes the light spread more even.  These strips will usually have 60 chips per metre.

 

Depending on what you want the strips for, I suspect that 5050s will be OK for decorative RGB strips, and they will generally draw around 0.8 to 1.2 A per metre with all the LEDs on, less when only a single colour is on.

Edited September 9, 2017 by JSHarris

[MikeSharp01]

46 minutes ago, JSHarris said:

Depending on what you want the strips for, I suspect that 5050s will be OK for decorative RGB strips, and they will generally draw around 0.8 to 1.2 A per metre with all the LEDs on, less when only a single colour is on

Thanks Jeremy. OK so I have two 4m Strips which is about 4.8A in total fed from both ends I can get away with 2.4A in the return and 800mA on each line (assuming they are wired as three colour signals and one return [0V] connection). I think that means the DEF STAN 16-2-4A cable I have should be fine, I think I may have some screened stuff somewhere but I suspect not need. Will bring it down and pull it in on Monday.

[Jeremy Harris]

No real need for screened cable, unless you're going for very fast colour changes and are concerned about switching transients causing EMI.  16-2-4A cable is OK, it's rated at 2.5A with all cores loaded, so will tolerate more than this with three of the cores carrying a lower current, just need to watch for the voltage drop, really (about 40mV per core per amp per metre).