power supply for LED strip

[Tony Davis]

Advice please, and a bit of clarification.

 

I purchased from Ebay 2 meter strip of LED lights to illuminate my layout. I enquired of the supplier as to what sort of supply was needed and their reply was "we suggest 12V 2A per meter for you", am I correct to assume they mean a 12v 4A supply?

 

Can anyone recommend a suitable supply, please?

 

Thanks

[dhjgreen]

24 Watts for a metre sounds like they are very bright, but if correct yes 4 Amps for 2 metres.

[John ks]

24 Watts per metre (24W/M) sounds a lot to me unless they are very very bright as dhjgreen suggests.

I did a quick look for LED strings & found differing results, EG 12W/M, 4.5W/M, 4W/M

The way to be sure would be to set a multi-meter to amps & measure the current drawn by the LED strip

 

John

[Harlequin]

If, by "strip" you mean a length of LED tape, then 24W per metre tape usually needs a 24V power supply and that will be printed on the tape itself.

 

[Crosland]

8 hours ago, Harlequin said:

If, by "strip" you mean a length of LED tape, then 24W per metre tape usually needs a 24V power supply and that will be printed on the tape itself.

 

 

The OP didn't say that. He was recommended to supply 24W for 2 meters. As Keith points out below, this was incorrect.

 

The ones I have used are more like 12V, 3A for 5m.

Edited March 3, 2019 by Crosland

[Grovenor]

Hi Andrew, you are misquoting the OP. He said 2A per meter at 12V, last time I checked 2*12=24.

Anyway a 4A  power supply should be fine, always better to be over rather than under powered.

Regards

[WIMorrison]

8 hours ago, Crosland said:

 

...

 

The ones I have used are more like 12V, 3A for 5m.

 

That is what the ones I use above my layout were quoted at also

[Tony Davis]

Sorry about the delay in responding.

 

Just after I posted the question I attended our local model show, I spoke to one of the traders there who sells electrical items and was told that a 12v 2amp transformer would be suitable for anything up to 5m. I took it home, connected it up, switched it on and nothing from the LED's. I got in touch with the trader who agreed to exchange the unit. When I exchanged it I double checked with him it's suitability. He assured me it was okay. In the meantime I had found a 12v 3amp transformer which did power the lights. My question is, bearing in mind the responses above is, would an higher current draw blow the transformer? I haven't tried the replacement unit yet as I don't want to damage it and also I can use the unit to power other stuff.

 

Thanks again.

[Junctionmad]

12V white light led strips tend to be around 5 -  7watts per metre , ie around 2-2,5 A, so a 3A system should be fine 

[cliff park]

Having a supply capable of supplying more than you need is never a problem. The unit will only draw what it needs and the power unit will be running at less than capacity, so will be happy

[Tony Davis]

So the 12v 2amp supply should work?

[WIMorrison]

Possibly a bit on the light side, if it isn’t  strang enough you will probably find that the lights come in, go off, come on, go off.... as the overload protection flicks in and out.

[Tony Davis]

Thanks Iain

[dhjgreen]

13 hours ago, Junctionmad said:

12V white light led strips tend to be around 5 -  7watts per metre , ie around 2-2,5 A, so a 3A system should be fine 

At 5-7 W per metre that is just over 1 Amp for 2 metres.

[Brian]

Amps are watts/volts. Therefore 5watt/mtr at 12 volts is 5 / 12 = 0.417Amp,  while 7 watts/mtr at 12 volt is 7/12 =  0.58Amp  times the number of units (metres).  So 5watt/mtr at 12 volt with 2 Mtrs in use is 0.834 Amp and at 7watt/mtr at 12 volt with 2 mtr is 1.16Amps.

Edited March 7, 2019 by Brian

[Junctionmad]

19 hours ago, dhjgreen said:

At 5-7 W per metre that is just over 1 Amp for 2 metres.

Indeed , it is , I severely admonished my calculator 

[John ks]

Just measured the current on 4 * 5M strips & got 1 @1.6A , 2@1.9A & 1@2.3A

Worst case for the above strips is about 0.92Amps for 2mtr

 

As I mentioned in an earlier post is if you got a multi-meter then set it to current & measure the current

 

John

[Coryton]

On 07/03/2019 at 09:15, cliff park said:

Having a supply capable of supplying more than you need is never a problem. The unit will only draw what it needs and the power unit will be running at less than capacity, so will be happy

 

Most things will indeed only draw what current they need, no matter how much current is available, if  they are working properly.

 

But that's not true if there is a short circuit, and what you don't want is a power supply capable of putting more current into the wiring than it can stand if there is a short circuit.

 

So to take a silly example, using a 100 A supply on a DCC layout would not be a good idea, even though in normal operation it wouldn't do any harm.

 

(Unless you have a fuse or similar to protect the wiring, of course).

 

 

[CloggyDog]

My micro layouts use around 1.5-2m of LED strip lighting, usually 1 length of cool white and 1 length of warm white wired together.

 

I power them off a 8 x AA battery pack with rechargeable batteries (2400MA/h). A full charge will easily last a whole day at a show.

[CloggyDog]

18 hours ago, Graham1960 said:

Why don't use a reconditioned computer power supply? They are fully protected and in the long run would save money on batteries. Presumably there's a standard mains supply at these shows or how would they run the trains? 

Most of these LED lights can be run off one of these. I dare say they are cheaper than power supplies from the model railway trade.

 

I could, but I rather like being 'mains-free' at a show - for my micro layouts I also run trains using a battery controller (detailed elsewhere, but basically 6 x AA rechargables, a PWM module and a DPDT switch in a RUB, cost less batteries of under a fiver)