LED lighting

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Unless I've missed it, no-one seems to have mentioned an issue that plagues me here (although I suspect a few "it didn't work" posts might be related)...

In trying to replace existing low-voltage halogen capsule lights of various sorts, with equivalent LEDs, I find that the LEDs don't work, because they don't provide enough of a load for the transformer.

One amusing example was our bathroom vanity unit, which had two halogen G4 capsules, which blow regularly. Last time one blew, I replaced it with nice round flat LED: http://www.amazon.co.uk/gp/product/B005MFALW0 - worked perfectly. That's running one halogen and one LED.

When the second one blew, I did the same: now neither light works. One halogen and one LED was enough load for the tramsformer, but two LED are not.

A similar problem arises with our mains voltage ceiling fixtures. the fittings have 6 x G9 capsule, and came with hloagen. I used a G9-BC converter and replaced with CFL, and then LED. Works perfectly.

Then, I try to fit a Lightwave RF wall switch, for this light, to operate it remotely: no good. The LEDs don't provide enough load for the Lightwave RF switch to run.

I think someone made a similar point re dimmers, but I'm not even trying that.

So I think I need to replace all the relevant transformers (for the 12V lighting); what a nightmare that will be (in the ceiling void, loft, etc).

Has no-one else run into this? am I confused?
 
I mentioned dimmers, but so far all the discussion has been about 240V operation. I have never been a fan of low voltage halogen (car headlamp!) lighting, for exactly the reasons above.

Have you googled for a solution?

In summary re dimmer switches: you need to fit specifically "dimmable" LED lamps and use a dimmer switch designed for them (the control characteristic needs to match the control curve of the LEDs to be effective). A standard dimmer rated 60W minimum still worked driving 3 LED lamps, but the control law is crap.
 
cdmackay said:
In trying to replace existing low-voltage halogen capsule lights of various sorts, with equivalent LEDs, I find that the LEDs don't work, because they don't provide enough of a load for the transformer.
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My only experience is similar. My parents have 3 low voltage halogens on a transformer over their kitchen sink. We could replace 2 with LEDs, but replacing the third stopped them all from working. Just left it with 2/1 but will have to consider an LED driver in the future.
 
I imagine there are transformers specified for LED operation. The mistake is to put the transformer itself somewhere inaccessible.
 
The bulbs on ledlam.co.uk claim to work with most 12V AC/DC transformers. I haven't tried those yet but have been pleased with their standard B22 240V bulbs.
 
I feel a 'QI' Klaxon. may go off here but, it must be remembered that whereas 240v LED lights are designed to work on a.c., some lower voltage ones require d.c. and will not operate when supplied by a 12v a.c. transformer used to feed halogen lights
 
That doesn't explain why the above two examples work when there is still one halogen in the circuit.
 
Black Hole said:
That doesn't explain why the above two examples work when there is still one halogen in the circuit.
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No it doesn't, to quote a regular user on this forum, 'that was for the benefit of other users' :)

The only thing that springs to mind with this 'loading' problem, is switched mode power supplies that only operate correctly when supplying a certain current, however I wouldn't describe a SMP as a transformer, it doesn't even have a transformer operating at 50 Hz
 
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The term transformer is overused...
All will have a transformer inside, but often more.
If they are DC, then there will be a rectifier and very possibly a regulator. Regulators often will not work without sufficient load.
And as Ezra mentions, there are Switch Mode Power Supplies. More popular nowadays because of their improved efficiency, will have a substantial amount of control and regulation circuitary; again, the regulator may need a minimum load to operate.
For LEDs, the term used is an LED driver, which is just another way of saying a SMP designed for operation down to low loads.
 
I would agree with most of that, but I would say a LED driver is designed to feed a 'LED only' device that has little or no other circuity, such a device not only requires d.c. but also requires a constant current supply (or at the very least a current limiting supply) rather than constant voltage, notice that this example has a voltage range and a specific constant current output :-

IMG_5643.png
 
hairy_mutley said:
The term transformer is overused...
Click to expand...
Quite, but that's just us electronics types being very specific by what we mean. Regardless of what's in the box, it transforms the mains supply into a supply suitable for the load - and the general public don't care what's in the box nor should they be expected to. So it's a transformer, even if it only comprises a chopper and a choke.
 
You correct in what you say, however you try using software when you should be using firmware, or any of the following, when it should be one of the others and see how long you get away with it before someone says you've used the wrong one :- Linux, Unix, Debian etc.
 
One also has to gauge the level of the discussion - whether the detail of the precise technicality is pertinent.
 
close(can->worms);

anyway, thanks all for the very helpful replies, with which I entirely agree.

Ironically, I do understand switched-mode supplies, but said "transformer" because I didn't want to sound too pedantic :)

Ours aren't actually in the ceiling void, I've remember, they're hidden behind some trunking, or in the loft, but still a bloody pain.

I don't see any solution for the Lightwave RF kit, sadly, until they bring out an LED capable switch.
 
In our previous house we had a lot of 12V halogens. Only a couple were powered by actual transformers. All the others were the electronic types and all had minimum loads.
I've just had a quick poke on Amazon and looking at two examples both are limited - one is 20-105VA and the other is 20-60VA. The page description doesn't always include this info but if you zoom the picture you can read the printing on the device.

So even though the LED may be specced as happy to work with an halogen 'transformer', the reverse may not be true unless you have enough LEDs on it (or a halogen as well).
 
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