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Cable: for Connecting a transformer to an LED strip


ToughButterCup

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I recall our electrician just soldering some white two core cable to the end of the strip and wiring the other end into the transformer.

 

Stranded i suspect as its more flexible (was put in at first fix) and easier to solder. In my experience,  solid has a habit of snapping off at the end.

 

@ProDave is the qualified person here!

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Speaker wire is probably what you want.  I would just look in one of my boxes of cable and see what I have.

 

A common misconception is "it's only 12V I can use a bit of bell wire"  but the fact it is lower voltage means it's higher current.  Pretty irrelevant for led strips but I have seen some horrors where people wired strings of 12V MR16 halogen lights with inapropriate cable.

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1 minute ago, PeterW said:

You can buy the correct cable and the connectors [...]

 

DickHead (@AnonymousBosch ) walks into an electricians and asks for  

 

"Erm that two core cable stuff for connecting drivers - no transformers - to LED strips"

"Well, sir would that be  [ @Onoff @ProDave @Jeremy Harris babble - white noise, - feel like a pratt ]  or perhaps simple bell wire?"

" I dunno "

 

I need to connect the transformer (some 12s, some 24 s to the LED- maximum length of cable, 2m, maximum lenght of LED 2m ) in such a way as I can swap out the driver when it decides to throw a hissy fit. I know what to use to connect the two core cable to the end of the LED strip. This section of the cable will be burried in the plaster, so I need to be sure to use red and black cable so I get the polarity right. 

 

Whats the CORRECT cable called ? Please. Pretty please. I just want not to look and sound like a right numbskull when I go to my suppliers.

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If you just need wire.... 0.5mm^2 red and black speaker cable..

 

https://www.ebay.co.uk/itm/10-METERS-2-X-0-5MM-Red-and-Black-Speaker-Cable-Auto-HIFI-Boat-speaker-wire/152132141794?hash=item236bc842e2:g:feQAAOSw-dBTv8Um&redirect=mobile

 

If you need  connectors each end these will be specific to the make of LED fitting.

Edited by Temp
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We've had to power up two 5m lengths of 12v LED strips, where the driver is 4m away from the start of each LED strip.

 

I used 2 core 1.5mm stranded wire https://www.screwfix.com/p/nexans-round-flexible-cable-3182y-2-core-1-5mm-x-25m-white/186fk  which is a bit OTT but I was concened it might be carrying quite a high current. It's quite thick to thread through the loftspace but works fine.

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Is red and black actually “correct” to use? Not that it really matters and nobody is going to be bothered for an application like this but my understanding is that by the regulations the normal brown and blue colour codes apply: blue for the earth-referenced voltage (often, but not necessarily, negative) and brown for the other one. I'm moderately but not completely sure that just using ordinary lighting cable wouldn't be “wrong”.

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Good question. 

 

Some LED transformers come with 4 wires pre-fitted. These typically use Blue and Brown for the Neutral and Live, and Red and Black for the output to the LED. A few use a pair of white wires for the output to the LED.

 

Examples

 

Red & Black

https://uk.rs-online.com/web/p/led-drivers/1314709?cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Displays_And_Optoelectronics-_-Led_Lighting_System_Components|Led_Drivers-_-PRODUCT_GROUP&matchtype=&pla-448230579044&s_kwcid=AL!7457!3!243856786484!!!g!448230579044!&gclid=CjwKCAiAlajvBRB_EiwA4vAqiBjcwAYuXAuSTLcWupBLaDa8c9_zxDSwP5aH7y6xnNez7IjKBjWLOxoCFmUQAvD_BwE&gclsrc=aw.ds

 

White:

https://www.amazon.co.uk/LED-Driver-Transformer-240V-Interference/dp/B00BMBKHC2

 

 

In the regulations..

 

Mains voltages (eg 240V) are "Low Voltage" or LV

LCD voltages (<50V) are "Extra Low Voltage" or ELV.

 

Not sure if this is current but..

 

 https://electrical.theiet.org/media/2063/bs-7671-2018-corrigendum-dec-2018.pdf

 

It says..

 

Quote

 


Control circuits, ELV and other applications

Line conductor    L     Brown, Black, Red, Orange Yellow, Violet, Grey, White, Pink or Turquoise

Neutral or mid-wire  N or M  Blue
 

 

 

I believe both of the wires between the LED controller and LED lamp should be treated as line conductors so you could use any of those colours. 

 

Edited by Temp
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On 06/12/2019 at 07:47, AnonymousBosch said:

Morning all. It's Friday! ?

I smile to cover the embarrassment of not knowing what the cable that connects the LED strip to the driver is called. You know- I hope - the thin red and black stuff. Should it be solid or stranded?

 

LEDs need DC not AC and hence the "transformer" need to both drop the voltage and convert to DC. In cheap transformers this might just be a bridge rectifier (simple AC:DC convertor)

 

LED strips normally have a visible + or - sign

 

BTW The word "transformer" is normally used as a term for voltage changes in the AC domain only.

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12 minutes ago, SteamyTea said:

As LEDs are DC, polarity is important, so if getting white cable, one needs to have a maker on one side of it, or it just becomes a pain (unless the rectification is done at the lamp end).

 

And thats why I'd prefer to use cable with red and black strands. How would I know if the retification is done in the LEDs themselves (... more expensive I bet?)

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2 minutes ago, AnonymousBosch said:

 

And thats why I'd prefer to use cable with red and black strands. How would I know if the retification is done in the LEDs themselves (... more expensive I bet?)

 

It's highly unlikely that the rectification is done in the LED strip.  Post a photo of 6'/150mm of your strip

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11 minutes ago, AnonymousBosch said:

How would I know if the retification is done in the LEDs themselves

 

7 minutes ago, Adrian Walker said:

It's highly unlikely that the rectification is done in the LED strip

Yes, very unlikely, but who knows what happens in the mind of electrical engineers.

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17 hours ago, Temp said:

LCD voltages (<50V) are "Extra Low Voltage" or ELV.

 

Not sure if this is current but..

 

 https://electrical.theiet.org/media/2063/bs-7671-2018-corrigendum-dec-2018.pdf

 

It says..

 

 

It also says for DC power circuits:

 

Quote

 

Two-wire unearthed DC power circuit

Positive of two-wire circuit  L+  Brown

Negative of two-wire circuit  L-  Grey

 

Two-wire earthed DC power circuit

Positive (of negative earthed) circuit  L+  Brown

Negative (of negative earthed) circuit (2)  M  Blue

Positive (of positive earthed) circuit (2)  M  Blue

Negative (of positive earthed) circuit  L-  Grey

 

(2) M identifies either the mid-wire of a three-wire DC circuit, or the earthed conductor of a two-wire earthed DC circuit.

 

 

So, as I said for brown and blue but with grey for negative if it's not earthed.

 

Personally, I think I'd just use ordinary 2-core 1mm² lighting cable, brown for positive, blue for negative. If the “transformer” says the output is unearthed (or it doesn't take an earth on the input side) then it would be slightly better to sleeve the blue in grey.

 

I haven't looked, can you even get 2-core solid cable these days? I assume you can get flex for plastic pendant lights.

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1 hour ago, AnonymousBosch said:

Its also the case that the "thingamajig" that takes a/c and makes it DC sometimes also called a driver isn't it? Why?

 

I seems to me that regarding LED power supplies the word “transformer” is (ab)used to mean something with a constant (¹) voltage output whereas “driver” is used to mean something with a constant current output.

 

(¹) albeit perhaps very ripply voltage, but anyway, not functionally current limited.

Edited by Ed Davies
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