On LED lamps, and powering them

[ban-all-sheds]

When everybody used LV incandescent lighting, you could go into any shop which sold them and bought any lamp which fitted your lamp holder, and know it would work.

With ELV lighting you could walk into any shop which sold them and bought any lamp which fitted your lamp holder, and know it would work, subject to the min/max range of the transformer(s) or electronic transformer(s) you were using.

With LEDs I do not think that cramming the as-cheap-as-possible components into the lamp packaging needed to make an intrinsically ELV emitter work with a voltage of magnitude 100x too high is a sensible idea. If one had no constraints, I don't think that anybody would come up with the idea of taking a 3-5V emitter and suggesting that in their millions they should be made with integral components which would allow them to be connected to a 230V supply. With a blank sheet of paper, people would think you were bonkers.

Of course, retro-fit compatibility is a real and significant constraint.

Today.

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?

 

[333rocky333]

I think it was more to do with the pending banning tungsten and halogen and trying to make something to replace them before they implemented it, no one really took to cfl as they were originally slow and dim to start.

With 240 unless dimmed im not aware of any issues with led, apart from the cheap components in some.
With 12 volt it seems the lamps are ok, its generally the 12 volt source thats the cause.

It seems only a few years back when they finally managed to get electronic transformers compatible with most dimmers and they had been around years, only to adapt now to Led.
I think another 5 years before things are more sorted regarding compatibility, though I foresee the demise of 240 volt domestic lighting and possibly 12 volt distributed around the house from a central box, with wi fi , sensors etc and a lot more automated

 

[John D v2.0]

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.

 

[ban-all-sheds]

Lights in series would not be very popular.

 

[ericmark]

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.

Been there done that, in a farm house all the lights were 24 volt DC and the light in the hall was powered through diodes from bedroom lights so when anyone switched on a light to go to loo there was light all the way. It was powered from a bank of NiFe batteries with a charger from generator or wind and worked well.

However this was on a farm on the Falklands with no grid power. Most the bits where from a bus which was bought to make a green house with.

In the UK dimmer switches etc are the problem, and with a DC supply the cost of dimmers would be even higher, so in real terms 12 volt is only for bathrooms where 230 volt is not permitted, if you can use 230 volt then that is the best option, and if you can arrange more or less lamps instead of dimmers that is also an advantage. Even if the selection of how many light is on the fitting.

 

[bernardgreen]

Lights in series would not be very popular.

Series - parallel switch of a pair of similar incandescent lamps provides ine level of dimming.

all the lights were 24 volt DC

A few "eco warrior" off grid homes have used 12 or 24 volt supply for lighting. Pulse width chopping provided dimming and, more importantly. saved power when full lighting was not necessary. A 555 timer, a MOSFET, a control potentiometer and a couple of capacitors were all that was needed for a dimmer.

There is a school of thought that incandescent filaments last longer on an AC supply ( or DC with regular reversals of polarity ). Migration of metal atoms across the join between the tungsten filament and the support wire is believed to weaken the filament if the migration continues always in the same direction.

Switch mode power supplies with a switching frequency that is ( or has harmonics at ) the mechanical resonance frequency of the coiled filament are known to shorten the life of a filament.

 

[John D v2.0]

Lights in series would not be very popular.

Not sure why not, in fact - a lot of the LED bulbs you can buy today are actually several wired in series. Since LEDs don't blow the way Christmas lights did, it should be fine.

 

[John D v2.0]

Been there done that, in a farm house all the lights were 24 volt DC and the light in the hall was powered through diodes from bedroom lights so when anyone switched on a light to go to loo there was light all the way. It was powered from a bank of NiFe batteries with a charger from generator or wind and worked well..

Clever, once you get into such low voltages you can have a good tinker with components you have lying around!
Although I was actually meaning LEDs themselves in series within a lamp, not the actual lamps as a whole.

 

[Gerrydelasel]

I do not think that cramming the as-cheap-as-possible components into the lamp packaging needed to make an intrinsically ELV emitter work with a voltage of magnitude 100x too high is a sensible idea.

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. So no, I don't think it will ever happen. Far more likely they will develop 240V LEDs that need no SMPS.

 

[bernardgreen]

Far more likely they will develop 240V LEDs that need no SMPS.

They DO need a SMPS driver to control the current flowing through the LED element(s) ( or they have 80 LED elements in series at approx 3 volts per element and a resistor to limit the current with a just a few volts across the resistor )

 

[Gerrydelasel]

They DO need a SMPS driver to control the current flowing through the LED element(s) ( or they have 80 LED elements in series at approx 3 volts per element and a resistor to limit the current with a just a few volts across the resistor )

Yes, that's how they currently work...

 

[ericmark]

The problem is there is often nothing on a bulb which says SMPS is used or a capacitor is used to control the LED's in the lamp. All they have to do is declare if the lamp in not dimmable they don't even have to say what dimming unit will work with it.

I used a simple bulb is series with my soldering iron for years with a switch to short out bulb when ready to use soldering iron. The cine lights also had series / parallel switching as a bulb saver, this has been done for as far back as I can remember. But with fluorescent and LED it's not that simple, using transformers in series (wire wound) it is possible but no real point, until we start putting labels on the bulb to say how they can be controlled you can't really do anything as to series / parallel switching.

What it would need is yet another bulb holder, with a new bulb holder you can do what you want, only bulbs with that new holder will fit, so you could do the same as done with fluorescent and have it so you only change the LED and don't change the control gear. Since the LED is a current device you can vary the current to a series of LED in series very easy, Set the max to LED max say 320 mA and you can reduce as you want.

What I don't know is if you put 160 mA through two 320 mA LED's how does the light output compare with that of one LED fed with 320 mA? In other words is it better to dim or better to use less?

Near every bulb has an array of LED's not just one, OK some complete lamps use a simple LED chip, but the bulb tens to have many LED's so question is as the lamp is dimmed should it switch off LED's in the lamp or reduce current through all LED's in the lamp? I think likely best option is to switch them off?

If my guess is right then next question is how do you make it so you can switch off selected LED's?

I am sure it can be done, the unit needs to read a signal from the dimmer, it may read the wave form shape as a command to switch off LED's, once the control unit has been developed into a chip then it would be cheap, but until then it will mean the units are more expensive.

At the moment the LED can give 100 lumen per watt but only gives around 70 lumen per watt due to using cheap control methods plus allowing for some control current to flow through the bulb so dimming switches can work. The latter is all well and good with one bulb, but if you like me have 10 bulbs in a room, then every bulb is using extra power just in case I want to use a dimmer switch.

As to the life of LED bulb, is it the LED that fails or the capacitor? If the control and LED are separate then you can change one without the other and reduce the problem of disposal.

 

[aptsys]

What I don't know is if you put 160 mA through two 320 mA LED's how does the light output compare with that of one LED fed with 320 mA? In other words is it better to dim or better to use less?

The efficacy of LEDs is significantly higher at low currents, mainly due to thermal effects. The 100lm/W+ quoted for many power LEDs is right down below 10mA. On a standard 1W power LED, between 250 and 350mA you may only see a 15% increase in luminous intensity.

 

[ianniann]

There are already some LED lamps designed to run directly from ELV DC, in some cases only from DC. These tend to be based around the G4/G5.3/G9 pin bases. Plenty of vehicles and boats running lights essentially from a battery source, but I don't see it catching on for most homes any time soon. The technology to convert mains AC to whatever DC a particular lamp wants is cheap, and while it isn't very efficient it wouldn't be a whole lot more efficient to do it all in one big unit and run all that current over long lengths of wire. A first step might be to have light fittings with one SMPS to feed multiple lamps but even that doesn't seem to be happening. Each lamps needs its own voltage smoothing and current regulation circuitry anyway, and for reliability the manufacturers may prefer to also be responsible for regulating the whole power supply. Look at all the compatibility problems between MR16 and the various (admittedly mostly AC) legacy ELV sources that are out there.

 

[ban-all-sheds]

Series - parallel switch of a pair of similar incandescent lamps provides ine level of dimming.

But we are not discussing incandescent lamps.