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LED lighting Wire/ Powersupply size questions??????????
LED lighting Wire/ Powersupply size questions??????????
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Old 11th January 2013, 10:58 AM   #1
Video Freak is offline Video Freak  United States
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Default LED lighting Wire/ Powersupply size questions??????????

Hello all, Dunno if anyone can help here( if you have a better( more appropriate) website suggestion for this question Im all ears) But here's my story. Im well versed in regular house wiring but less so with 12v led wiring situations. My question is kind of long:

Im looking to wire a " main 12v trunk line" in my basement so I can tap off of it to supply led lighting( strip lighting) to various closets and under toe kick "night-lighting" on my 1st floor. in total I suspect Ill probably need 10-15 meters of total 5050 SMD lighting cut into around 1-2 meter sections each. The main trunk Line would be 40ft long and have tap-in lines at most 10 ft long to the various closets toe-kicks etc. Im struggling with what size power supply I would realistically need and more importantly wire size of the " main trunk" to prevent too much voltage drop. I would get something along the lines of the following


A side question: is the above strip is rated as 1.2a/meter and I know from messing around with a previous RGB strip-light that these can be grossly underpowered current wise. Example is I have a RGB 5m 5050 that I can power with 12v and 0.5amps( is it that these manufacturers state Max values for Current or what gives with this anomaly?)

I will try and attach a crude drawing of what I want to achieve: Some notes The closets will use 12v magnet switches so they only turn on when the doors are open and the toekick nightlight parts only turn on when a photocell senses that its " night time" The picture will show the wiring diagram done in the basement( this is a 4 year old site built ranch) and then I will run the individual offshoots from the trunk-line in the basement to the specific locations

Side note I intend to place the PS in the middle of the run and have (2) 20foot leads as opposed to the PS at the end of 40 ft as shown in the picture.

So question is will this work? what size wire for trunk-line vs the individual lines? Can I assume I can plan for a lower current draw from these strip lights then stated numbers? Any help is appreciated

Link to picture Diagram::::::::::::::::::::::::::::::

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Old 11th January 2013, 11:06 AM   #2
madtecchy is offline madtecchy  England
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Location: wigan
create a ring with your 12 volts.

regards Mark
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Old 11th January 2013, 11:17 AM   #3
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
I took delivery of LED replacement lamps yesterday.
Did some tests.
The MR16 5.5W 12V lamp is a 27LED 5050. This draws 280mA when fed with 12Vdc. But it has an unlabeled 2pin pin plug that can be swapped around. When I swap the polarity it still draws 280mA @ 12Vdc.
The current draw increases to ~370mA when the voltage is reduced to ~9.8Vdc of either polarity.

It works with both polarities !!!!
I wonder if it works on 12Vac?
It does. And it's brighter
It draws 450mAac, when fed with 12Vac.
They are described as not dimmable. But the dimming is quite effective, as I rotated the Variac to below nominal 12Vac. It also dims on DC, works with similar white but reduced light output down to about 1W when on 9Vdc (110mA). Lower than that looks a bit odd.
At full rated voltage the light output is considerably less than a 35W halogen MR16. Yet they claim equivalence to 50W halogen MR16.
I will returning all 26 of them because they are not as described.

In answer to your question. Each lamp will be in parallel with all the others. Each will draw it's rated current when fed with rated voltage.

5 bulbs switched ON at the same time will therefore draw ~2.3Aac (27.5W of LED power)
regards Andrew T.

Last edited by AndrewT; 11th January 2013 at 11:21 AM.
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Old 14th January 2013, 12:07 AM   #4
Video Freak is offline Video Freak  United States
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Thanks for the replies any other ideas from anyone? I decided to put the PS in the middle of the " line" nad make (2) 20foot legs as opposed to (1) 40 foot long one too.
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