On LED lamps, and powering them

[ban-all-sheds]

However....

Wouldn't be that hard to switch over the whole lighting circuit to 24v DC, it would mean changing things like bathroom fans and whatever else, but there wouldn't be much load on a lighting circuit.
But even though one led needs less than 5v, running them in series is better for balancing the current, so it's best not to run on too low a voltage.

John, I believe, was talking about individual LEDs in series within a lamp, or a luminaire, and therefore advising against an ELV lighting circuit being too low a voltage.

I didn't think about that, and was talking about individual luminaires throughout a room or a house, etc, being in series.


[EDIT]Spleling misteak corretced[/EDIT]

 

[ban-all-sheds]

SMPS have become so ubiquitous within every possible electronic device that to redesign the mains supply purely so lamps don't need to contain SMPSs would be misdirected effort. 99% of the electronics industry would be using SMPSs as usual, and continuing to plow R&D into greater efficiency, and the only odd-ones-out would be the lamp makers.

I wasn't suggesting redesigning the mains supply...

Sorry if this caused any confusion for people because it mentioned mixing'n'matching LV and ELV:

Does the team think that there will ever come a time when LED lamps can be mixed-n-matched with power sources the way that LV and ELV incandescents can be today?

What I meant was that I can go out and buy any regular BC/ES/SES 230V incandescent lamp, and know that if it goes into the luminaire it will work in my house.

[EDIT AIMED AT THOSE WHO WANT TO DISREGARD "incandescent" IN THE QUESTION I WAS CLARIFYING]

And that (more to the point) I can go out and buy any incandescent 12V lamp and match it with any 12V incandescent lamp supply, be that a transformer, an electronic transformer or a battery and know that it will work. (AFAICT the use of anything other than 12V for domestic ELV lighting is somewhere between rare and unknown.)​

[/EDIT FFS]

What I'm wondering is if the day will ever come when I can go out and buy any LED lamp supply and any LED lamps and have them work together with the same assurance of success that I have today with 12V incandescents? Will there ever be as wide a choice of luminaires designed to take ELV LED lamps (at whatever voltage emerges as a de facto standard) as there is today with LV BC/ES/SES lamps?

 

[ericmark]

And that (more to the point) I can go out and buy any 12V lamp and match it with any 12V supply, be that a transformer, an electronic transformer or a battery and know that it will work. (AFAICT the use of anything other than 12V for domestic ELV lighting is somewhere between rare and unknown.)

Not really true, 12 volt LED lamps come as both AC and DC and often it actually stipulates the frequency with AC types, although you may be able to get a unit which changes AC at MHz to AC at 50 Hz this would likely cost as much as getting a wire wound transformer, and DC lamps may have a rectifier so polarity does not matter, but likely with AC they would not work correctly, if I had a DC LED at the cost I would not want to try it on an AC supply, 3W at £8.50 is a bit expensive if you don't need a DC MR16 lamp.

As to AC the lamp marked 50 Hz may work with a switched mode supply at MHz but for how long and will it cause interference?

I bought some very cheap MR16 G5.3 0.58 watt bulbs, I also got some MR16 GU10 0.58 bulbs. The 230 volt are still working, all the 12 volt have failed, it was a wire wound transformer so they should have been OK, but they lasted around 4 months only. And this is the problem with 12 volt lighting, it may work to start with, but how long will they last? When a switch mode supply starts to shut down on under current it may work OK for 4 months, but will it work for 10 years?

There has always been a problem with 12 volt. We call it 12 volt, but a lead acid battery with a stage battery charger can be 11 ~ 14.8 volt, where there is no regulation it can go higher, a standard RB106 regulator is set to 16 volt open circuit so we have to expect that voltage. Lamps designed for supplies from mains expect slightly under 12 volt, but with a battery that is not the case.

 

[ban-all-sheds]

And that (more to the point) I can go out and buy any 12V lamp and match it with any 12V supply, be that a transformer, an electronic transformer or a battery and know that it will work. (AFAICT the use of anything other than 12V for domestic ELV lighting is somewhere between rare and unknown.)

Not really true, 12 volt LED lamps ...

Oh FGS - despite the fact that I wrote that clearly in the context of incandescent lighting, you had to go and make that petty "correction".

OK - see the edit I've now made.

 

[bernardgreen]

And that (more to the point) I can go out and buy any incandescent 12V lamp and match it with any 12V incandescent lamp supply, be that a transformer, an electronic transformer or a battery and know that it will work.

Do not over look the small but not insignificant fact that the some incandescent lamps have coiled filaments which creates an inductance which at 50Hz is trivial but at several kiHz may create mechanical forces in the filament. Destructive resonance may occur

 

[Gerrydelasel]

Do not over look the small but not insignificant fact that the some incandescent lamps have coiled filaments which creates an inductance which at 50Hz is trivial but at several kiHz may create mechanical forces in the filament. Destructive resonance may occur

Which is why he's asking whether there will ever come a day when that isn't the case, i.e. such incompatibility problems will be cleverly solved and standardised.

 

[bernardgreen]

, i.e. such incompatibility problems will be cleverly solved and standardised.

The various items ( transformers, drivers voltage sources etc etc) need to be properly documented and their function fully and clearly explained to the trade and the public who buy or specific the lighting they want. Until then the full extent of incompatibilty will not be understood and without that understanding the problems cannot be fully identified let alone solved.

 

[Gerrydelasel]

The various items need to be properly documented and their function fully and clearly explained to the trade and the public who buy or specific the lighting they want. Until then the full extent of incompatibilty will not be understood and without that understanding the problems cannot be fully identified let alone solved.

So... do you think that there will ever come a time when LED lamps can be mixed-n-matched with power sources the way that LV and ELV incandescents can be today?

 

[bernardgreen]

when LED lamps can be mixed-n-matched with power sources

I do not think that will ever happen as there are too many variables and too many errors and ommissions about LED lamps, LED elements and drivers have been irrevocably set in place in the minds of the public and the less well informed trades people.

 

[big-all]

if you get a 10w led chip it has 9 segments and can be set up as 9-12v which is indeed 3 groups off 3 segments wired in series then parallel
or the same chip wired full series gives you something like 29-33v
you off course buy them ready made rather than adapt
http://www.ebay.co.uk/itm/10Pcs-27-...791303?hash=item1c7b2f7247:g:VmsAAOSwjDZYiGtc

 

[bernardgreen]

if you get a 10w led chip it has 9 segments

That is one option, to be precise it is a substrate with 9 LED chips bonded to it. The substrate being a thermally conductive material to remove heat from the LED chips.

up as 9-12v

Provide there is a means to regulate the current through the LED chips then one can refer to the assembly ( lamp ) as operating on a 9 to 12 volt supply.

Some LED chips appear to work directly from a voltage source without any obvious means to control the current. SNEAKY but cunning design..... the LED chip has either (1) a resistive semiconductor layer under the light emmiting layer or (2) a current limiting circuit built in silicon under the light emmiting layer.

The resistive option is used in most 3 volt battery operated fairy lights

 

[ericmark]

I think what we need is better labels so we know what we are buying, there are three main ways to limit the current through a LED.
1) Resistor.
2) Capacitor.
3) Current regulated power supply.
The latter in general uses less power as often it has a switch mode system of regulation, often it can't be dimmed as the regulator will compensate for what any external controls do, and often has a huge voltage range, 10 ~ 36 volt DC or 100 ~ 250 volt AC and is clearly the better unit. And they use less power typically 100 lumen per watt. However they cost more to make, and are often DC only when extra low voltage type.

The resistor with a rectifier can work with nearly anything with right voltage, AC or DC, but it also is rather wasteful.

The capacitor is AC only and often it has to be correct frequency, they also normally have a resistor as well to allow for leakage current, because of the resistor not sure which wastes the least capacitor or resistor?

At the moment the LED lamp needs to state voltage and wattage and if not dimmable. They also often say DC only or 50/60Hz but nothing says they need that marking, Manufacturers seem to think the general public are thick, and they don't give basic information. There is an energy rating which is about as much good as a chocolate fire guard, ratings need to now start at below 50 lumen per watt and go to above 100 lumen per watt with may be 15 lumen per watt between each rating, below 50 lumen per watt any device giving out light is not solely for lighting, clearly a heat lamp gives off light, but it is used because of the heat as well, and Christmas tree lights are for decoration not for lighting the room.

If you look at the graph

from Wikipedia you can see A and A+ is well below 100 lumen per watt, the energy rating is not simple lumen per watt but uses some odd formulas and is shown as a percentage of what some standard lamp uses, A++ is 13% directional and 11% non directional and I have not seen a non directional LED lamp but for regulation it seems 120° is the demarcation.

I am sure like with freezers and fridges there is some where a PDF which shows exactly how the energy rating is worked out, however I have failed to find it. From this PDF as far as I can work out the standard energy consumption for under 300 lumen is about 10 lumen per watt, so it would seem above 91 lumen per watt is the point for A++, and between that and 59 lumen per watt for A+ below that down to 41.7 lumen per watt is A rated, well near all LED lamps are A+ very few are either A++ or A so what is the point of an energy rating which nearly every lamp is going to show same results?

 

[winston1]

The capacitor is AC only and often it has to be correct frequency, they also normally have a resistor as well to allow for leakage current, because of the resistor not sure which wastes the least capacitor or resistor?

Obviously the capacitor as capacitors are wattless on AC.

 

[ericmark]

The old way of heating a valve was

the main point is the valve has a set power requirement. It can be worked out with

F in the formula is frequency so it can be seen if the frequency is not 50 Hz then the impedance will also not be as designed. I would not expect an extra low voltage lamp to use a capacitor as a current limiting device, I would expect to find a resistor, however there is nothing to stop a manufacturer from using a capacitor so when the lamp is marked 50 Hz to power it in the MHz range is really to be avoided.

When I first saw the replacement MR16 ELV lamps I had thought they were DC and you needed to change the dropper to a DC type, but then I noted the 50 Hz marked on the lamp, this advert Screwfix does not state AC only, but the picture

has it written on the bulb "4.6W 345lm 410mA 12V 50Hz 2700K 36° 2016-3-9" So it would seem they are AC lamps or would not be marked 50Hz. BAS has pointed out some electronic transformers do have the output frequency marked, but not all, so that means the installer needs a frequency meter, now I do have a frequency meter and I can use it to set generators to 50Hz but as to MHz range I am not sure what it would show, I picked it up in Hong Kong while I was working there. This was before the take over and the instructions were lost years ago if I ever had any. Also sticking the probes into a MR16 holder is not easy.

In my house I know the transformer is giving out 50Hz, but in anyone else's house not a clue. With the early push for so called drivers which are not really drivers they have consent voltage not current, when we come to change a MR16 lamp we have not a clue if the supply is AC or DC or 50Hz or in MHz range. We also have not a clue if the bulb has rectifiers, capacitors, resistors or full blown switch mode driver inside. The document I linked to tells you what manufacturers must tell you, and it tells them voltage, wattage and amperage all need to be on the package when really it only need two the third is easy found using Ohms law, but it does not need to say AC or DC, that is crazy.

 

[bernardgreen]

I don't have the actual scope screen shot but this is very similar to the wave form found on the output of a SMPS 12 volt AC supply