How do I calculate LED Driver/transformer requirements

[lidster]

Hi,

Im trying to hook up some 5050 smd LED strip lights under my kitchen cupboards and just had a few questions regarding LED drivers/transformers.
the LED Strip is 5M in length and will be cut.
60 leds/Metre
input voltage : 12v
Working Current/metre: 1.2-1.25A
Output power: 72W /5 Metre
Luminous Flux: 700-800Lumens/Metre

I plan to cut the LED Strip into a 1.8 metre length for under the kitchen cupboards. Then I want to cut and join 2 more strips for under bookshelves in the front room 1.5m each (3metre in total). Ive done quite a bit of research already - but just wanted clarification on the below:

1)Do the numbers written on the transformers just show the max they can handle without fault?

so when buying a 12v transformer/driver do I just have to make sure the total max Watts is ample to drive the length of cut LED Strip?
eg. 3m requires output requirement of 43.2 watts - so I would need a 12v 50 watt transformer....

2)could I safely use a 12v 60 watt transformer on the 1.8m length (only 25.92 watts required)? Does it just draw the current it requires and as long as its less than the max capable - there will be no problem.

3)I tried a 12v 30watt laptop transformer on the full 5metres for 20 secs or so to make sure the lights worked. they came on but, what would happen if I left this running for 12 hrs or so? (just curious!)

4)Could I use old/2nd hand laptop transformers if the watts/amps are suitable for the requirements above, or do the bought "LED drivers" have special features that laptop tranformers dont have?

thanks for any help

 

[securespark]

What do the manufacturers of the LED strip say?

 

[lidster]

There is no manufacturer listed on the packaging. It was purchased on Ebay. Although a uk seller - it would appear it originates overseas

 

[ban-all-sheds]

If this is a new item, then AIUI it is an offence to sell it without adequate instructions.

You can't just connect any old 12V supply that you like to an LED light.

www.google.com/search?q=led+constant+current+vs+constant+voltage

Well - you can, but you must be prepared for the chance that things could go wrong - anywhere between it not working and it not working ever again. You may also find that short lengths don't meet the minimum load needed by the supply.

Get onto the seller and get him to step up to his responsibilities and supply you with instructions.

 

[lidster]

You can't just connect any old 12V supply that you like to an LED light.

Well - you can, but you must be prepared for the chance that things could go wrong - anywhere between it not working and it not working ever again. You may also find that short lengths don't meet the minimum load needed by the supply.

thanks for this - didnt consider the minimum load - that kind of answers my question ref the difference between led drivers and standard DC transformers.

I have ordered for £15 delivered a proper LED driver sold from a UK company at 30 watts.
I would still like to know though (in theory I suppose!) if this would safely power an LED strip that only needs 10 watts..... If anyone knows on here - then great - if not I will email them and ask

cheers for replys

 

[RF Lighting]

Yes a 30W LED driver will power any amout of LEDs upto 30W

It's not a good idea to use standard 'downlighter' type transformers with LEDs.

I fit loads of these LED strips as under and over cabinet lighting in kitchens. They're brilliant.

 

[sportsnapper]

@RF Lighting - any recommended suppliers for these? I'd like to replace the fluorescent fittings with led strip - but seems a bit of a minefield out there trying to select the right combinations...

 

[RF Lighting]

How much wattage of LEDs do you want to power?

 

[Chri5]

How much wattage of LEDs do you want to power?

At 14w per m, that would be 26w for the kitchen and 42w for the storage.

http://www.led-supplies.com/led-drivers-LED-power-supplies/12v-LED-Power-Supplies.html

 

[RF Lighting]

Hang on, there's two different questions running at the same time on this thread. I'll ask the mods to split it...

 

[sportsnapper]

No need - I was just looking for some recommended suppliers of LED tape and Power supplies - that people have used and are happy with - though re reading the question that's not obvious. I've since been searching the site and come up with a couple that are quite informative, and the link Chri5 supplied is a company that are quite close to me (everyone else seems to be up North). So I've got something to be going on with.

 

[lidster]

No need - I was just looking for some recommended suppliers of LED tape and Power supplies - that people have used and are happy with - though re reading the question that's not obvious. I've since been searching the site and come up with a couple that are quite informative, and the link Chri5 supplied is a company that are quite close to me (everyone else seems to be up North). So I've got something to be going on with.

I bought my LED strip off ebay. 5 metres for warm white LED 5050's waterproof cost £15 all in. no customs. I bought my transformer from LED Hut - an online uk company. all works fine and v happy with the results

 

[sergeantash]

Just a query, for fitting into a kitchen, to satisfy electrical regulations, did you fit an IP rated or waterproofed transformer? Is it necessary for regs?

 

[lidster]

Just a query, for fitting into a kitchen, to satisfy electrical regulations, did you fit an IP rated or waterproofed transformer? Is it necessary for regs?

sorry - dont know about satisfying building regs - but I used waterproof transformer/ led strip anyway......I think a waterproof transformer was only a few quid more than a standard one so worth the extra

 

[Taylortwocities]

Just a query, for fitting into a kitchen, to satisfy electrical regulations, did you fit an IP rated or waterproofed transformer? Is it necessary for regs?

The regs say that it must be suitable for the environment.
There are some locations where the IP rating is SPECIFIED by the regs, e.g. bathroom/swimming pool etc,