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Ballustrade lighting, RGB LED, Voltage drop, cable mm2

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  1. #1
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    Default Ballustrade lighting, RGB LED, Voltage drop, cable mm2

    I've got some left over ceiling LEDs in 9mm wide strip and am going to use 16x 100mm RGB strips for my ballustrade lighting.

    I've sikaflex'd 12mm square aluminium open channel underneath the handrails of the balcony balustrading with the open face down to allow me to run my cable and LED's.

    Apart from holding the wire in there...(regular segments of 10mm poly backing rod maybe), my main concern has turned to voltage drop along the 25m single series run.
    Currently I am considering (and have sized my holes everywhere) for 5 core Trailer wire 0.63mm2 per core from bunnings.

    Here's the stats 24V, 22W = 1amp roughly over 25-27meters - but this is over 4 conductors.
    RGB LED Strip connections require 4 core = an R, a G and a B + a 24V black. Flat out on white light....each RGB core would see only a third of the current. I assume the black is your "neutral" so it will see the full return 1Amp. Vdrop over this distance may be a factor so what I am thinking is utilising the spare wire left over in my 5core trailer wire for a second "neutral". Effectively doubling the mm2 area to 1.3mm2 on that 24V neutral.

    Originally I set about this calc to down size my cable as it is going to be hard to feed the 5 core trailer wire through some bends in post work etc....but my inital calcs tell me I dont have a "current carrying issue" (what I sized the cable on) - I may however have a "Vdrop issue".

    Comments appreciated.

  2. #2
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    For the hell of it - I did some testing last night with 10m of 4core telephone cable and the 16 LED modules.
    Estimated gauge of the cable 7 strands at 0.12mm diameter = 0.08mm2
    An almost ludicrous choice but no heating (to touch) - just thought I'd try it.

    Full power....
    Input voltage to the telephone cable....21.3V
    Current through the RG&B = 0.13Amps
    Current through the Black = 0.42 Amps
    Total Power consumption 8W - this was confirmed back at the 240V active to the whole system with Amps droping from 1.73Amps (415W) to 1.70Amps (408W) = 7W
    Voltage at the end of the telephone cable - 19.9-20V - drop = 1.3V

    Since I will be using 25 meters of the stuff, multiply the drop figure by 2.5 - bringing the final end voltage to 18V - but this doesnt effect the brightness much - I dimmed the units down to 18V to check and there was very little change.

    These LEDs are very high power and as I only want a subtle effect, I'm suspecting they will be run most of the time at a PWM dimmed capacity of 5-10V RMS.
    So I measured one at 4V and the dV along the 10m telephone cable was only 0.1V. Amazingly power consumption is in the order of 2-3 Watts...these little units are awesome for effect lighting. And they might last 50-100,000 hours that's 20 years...hopefully!!
    I'm going to run with this - although in hindsight I could have used 6 core and used 3 strands for the black (return).

    Never know unless you try.

  3. #3
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    Just a quick up date.
    Installed the telephone cable and 8 LED modules half the way (12m) and have V drop issues.
    Possibly because I have now multiple solder and twisted joints - although I wouldnt have thought that to cause too many issues. Probably only takes one. It seemed to be exacerbated with the installation of the last 1 or two modules (I check after each one is added).

    As a test, this intial hookup was added after a previous 5m strip of these RGB LED's. (I have 7 x5m strips in my ceiling cove).
    I will add a 24V amplifier between the preceeding 5m strip and this ballustrade run to see if that improves things. This will give 24V at the head of the arrangement instead of the 21V I was measuring above. I also have a couple of Plan B's.

  4. #4
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    Sorted the Vdrop issue - I had a short circuit pulling too many amps (4 versus 0.4A) and hence dropping the voltage. Have to improve my insulation as it sits in a 12mm aluminium square channel - in hindsight I could have used this as the main return conductor.

    b22b

  5. #5
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    Default Finished 1st Generation

    Completed the Lighting today. took more care with insulation to prevent further short circuits on the aluminium channel. Wires are finally held in with 10mm foam backing rod which can be easily removed as required/maintenance. Looking for 9mm as it might be a little more "in the channel rather than slightly proud of it.
    8mm is too thin
    1.2mm heat shrink tubing was used for all wire/module terminations - all 120 of them!
    I learnt not to shrink it - just use it as insulation - if you need to change out a module - it is much easier if the tube isnt shrunk and there is no movement - so shrinking isnt necessary - sometime things can be a little too permanent.


    2 Circuits -
    8 modules along 12m of 4core telephone wire on one and
    7 modules along 10m of telephone wire on the other.
    Voltage drops 24.1V down to 22.9 and 23V so pretty good. Pulling 0.33Amps and 0.39 Amps. So total power about 17W for 15 modules. Each 10cm module has 6 LED's.
    These LED's really crank. see photos below.

    Generation 2 - I would use 6 core telephone wire and double up on the modules whilst placing them at thirds between posts rather than at the centres - being closer to the stainless terminations, this tends to allow the light to spray onto the buckles and forks at posts rather than just the wires in the centre. The LEDs could also be dimmed further to only ascentuate the hardware....Someday later on.
    Attached Thumbnails Attached Thumbnails landingballustradewiredaytyime.jpg   landingballustradewirenighttime.jpg   landingballustradewirenighttimeblue.jpg   landingballustradewirenighttimered.jpg  

  6. #6
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    I was trying to work out how to "isolate it" or switch it off so there is no potential charged out to the handrail.

    If I just switch the black - then I presume there will be a continuing potential through the hand rail from the RG&B and in the case of minor shorts and leakage may charge my handrail with a potential - the consequences of which I do not know...corrosion etc..maybe.

    Can you see this as an issue and does that mean I'd have to either switch all 3 of the RG&B off or of course turn the power off the controller totally.

    See attach...

    s
    Attached Thumbnails Attached Thumbnails ledstriplightingswitching-isolationoptions.gif  


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