LED Driver advice.

[ban-all-sheds]

I have looked at MR16 LED lamps and most do not seem to mind what polarity or if DC or AC but some do

Most?

Lots actually. Any which look similar to this, for example, will require a 230V AC supply:

 

[bernardgreen]

A LED element ( just the light emitting diode ) must be supplied with a controlled current. An LED lamp will be an LED element with some means to control the current through it when a voltage is applied to the lamp.

Putting a voltage source with uncontrolled current directly to an LED element will almost always damge or destroy the element.

Some torches do appear to connect the battery directly to an element without any obvious current control. The current is limited by the internal resistance of the battery.

 

[JohnW2]

A LED element ( just the light emitting diode ) must be supplied with a controlled current. An LED lamp will be an LED element with some means to control the current through it when a voltage is applied to the lamp. ... Putting a voltage source with uncontrolled current directly to an LED element will almost always damge or destroy the element.

Indeed - but, as has been discussed, the correct use of terminolgy cannot by any means always be assumed.

What I would have hoped/expected that one could usually assume is that if an 'LED something' comes with a specified voltage (12V, 24V or whatever), then it really ought to be a true 'lamp', with built-in current control (even if only a resistor), such that it will work off a constant voltage source of the indicated voltage - but perhaps even that is not always the case.

Kind Regards, John

 

[greasedmonkey]

I would say that you just need a 12V supply. As most LED's are simply a diode that glows, they usually require a potential of between 1.8 and 2.2V. If these are cheap and from china, I suspect what you are getting is a diode and resistor in the package and not much else. I would think a true "driver" or constant current source would not be needed as the resistor value SHOULD have been calculated to keep the current correct at 12V.

 

[JohnW2]

I would say that you just need a 12V supply. As most LED's are simply a diode that glows, they usually require a potential of between 1.8 and 2.2V. If these are cheap and from china, I suspect what you are getting is a diode and resistor in the package and not much else. I would think a true "driver" or constant current source would not be needed as the resistor value SHOULD have been calculated to keep the current correct at 12V.

Indeed - that is precisely what one would expect. Up-market LED lamps may have a constant-current controller (rather than just a resistor) within them, but if they are described as "12V" (or 24V, or whatever - or maybe even something like 12V-50V, if they containing a constant-current controller) it's difficult see see what that can actually mean other than that they will work off a simple (essentially constant voltage) 12V (or whatever) supply.

Have said all that about what one would 'expect', whether one necessarily gets what one 'expects' when ordering cheap items direct from China is probably not a totally foregone conclusion.

Kind Regards, John

 

[DetlefSchmitz]

I suppose this may be of interest, can't remember if I posted them before. It's an LED replacement for a small 12V halogen lamp (G4). You can see the bridge rectifier, and some other stuff. I haven't bothered to work out the circuit so far, as the lamp is experimentally in use.

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• DetlefSchmitz
• 21 Oct 2013
• 1

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• DetlefSchmitz
• 21 Oct 2013
• 1

 

[julesg007]

Have asked the seller to confirm the correct type of power supply needed.

Will post again when I have a reply.

Thanks to all for your contributions to the thread.

 

[julesg007]

Got a reply from the seller, and they have stated that a simple 12v DC supply will be OK.

 

[JohnW2]

Got a reply from the seller, and they have stated that a simple 12v DC supply will be OK.

Glad they were able to confirm that. As I said, it was pretty difficult to understand what else they could have meant by "12V".

Kind Regards, John

 

[julesg007]

Going off at a bit of tangent I know but I'd be grateful for a bit of further advice as I want to supply the correct power supply to my electrician.

As I have 4 of the lights, what would be the best way to supply power?, do I need one transformer for each light or can they wired of a single transformer?

Thanks again for the help and advice!

 

[JohnW2]

Going off at a bit of tangent I know but I'd be grateful for a bit of further advice as I want to supply the correct power supply to my electrician. As I have 4 of the lights, what would be the best way to supply power?, do I need one transformer for each light or can they wired of a single transformer?

Provided that they are not miles apart (which I doubt), there's no reason why they can't all be run off the same (simple 12V) power supply. As you said in your initial post, a 20W (or 2A) 12V power supply would be more than enough for all four. Did you ascertain from the manufacturer whether there is a 'driver' (current controller) which has to go between the power supply and each lamp (or whether that is contained within the lamps?) - your electrician will certainly need to know that!

KindRegards, John

 

[ban-all-sheds]

Going off at a bit of tangent I know but I'd be grateful for a bit of further advice as I want to supply the correct power supply to my electrician.

You should have him provide all of the materials and equipment. You won't get any form of warranty for his work otherwise.

 

[JohnW2]

You should have him provide all of the materials and equipment. You won't get any form of warranty for his work otherwise.

The OP appears to have already bought the lamps, and quite possibly also associated 'drivers' with them, - so I think most of that horse has probably already bolted.

Kind Regards, John

 

[julesg007]

The lights are being used in a water feature and I want to make all of the connections in a waterproof box that is attached to the base tray of the water feature.

The tray gives me approx 200mm of useable height to attach a box to so I am trying to understand how to connect everything to determine the size box I will need to get.

As I am supplying the lights, as John has stated that horse has already bolted, and the electrician is more than happy to work on basis that I supply the items I want to use, but he will tell me straight that if I supply miss-matched items and he will refuse to install them. He is more than happy to stand by his work and I am more than happy to work on that basis, moreover as he is a fully qualified professional the manufacturers warranty will still be covered.