LED brightness question

[JohnW2]

The use in incorrect terminology is too deeply entrenched in common language. Nothing can change that now ....

If you changed "incorrect" to something like "unclear" or "ambiguous" then I would totally agree with you. However, as often discussed, if a particular use of language becomes sufficiently "deeply entrenched" and in very widespread use, then one has to question whether it really is sensible to call it "incorrect".

In any event, that's not really the point I was making. Sticking with your concept of "incorrect", I would personally say that what is 'incorrect' is to use the word "driver" to refer only to constant-current sources, whereas for many decades its 'correct' meaning has encompassed a whole range of other things, including constant-voltage sources.

By analogy, I don't think that even the most passionate supporters of the 'modern' use of the word "transformer" to refer to SMPSUs would dream of suggesting that it is no longer 'correct' to use the word to refer to a wire-wound 'inductive' transformer - but if they want/need to be unambiguous, they now have to qualify the word (e.g. with "inductive" or "electronic".

... What can be done is to try and explain the differences between an item and its common but incorrect title

What is absolutely crucial is that people understand what features of a product they have to specify in order to be unambiguous. If one wants something to power some item of equipment (whether LED lighting or anything else) it is just as important for them to specify whether it is 'constant voltage' or 'constant current' as it is to specify the required voltage or current and whether the output is AC or DC.

Kind Regards, John

 

[bernardgreen]

What is absolutely crucial is that people understand

The bottom line is that a driver drives one or more LED elements .

When packaged together that driver and those LED elements are an LED lamp.

An LED lamp ( driver and one or more LED elements ) requires a power supply that is acceptable to the driver that is integral to the LED lamp

 

[JohnW2]

The bottom line is that a driver drives one or more LED elements . When packaged together that driver and those LED elements are an LED lamp. An LED lamp ( driver and one or more LED elements ) requires a power supply that is acceptable to the driver that is integral to the LED lamp

I think you may well confuse some people with that statement.

Yes, in relation to any piece of electrical/electronic equipment (including an "LED lamp", or a string of LED elements) it is obviously crucial that the power supply is appropriate for ("acceptable to") the equipment - in terms of whether its output is AC or DC, whether it is 'constant-voltage' or 'constant-current' and what that 'constant voltage' or 'constant current' actually is [the word "constant" being an approximation to the truth in all cases!].

However, what may confuse some is that you now appear to be talking about "a driver driving a driver".

In any event, I don't think any of this alters my point that I personally consider it inappropriate that people should (I would say incorrectly) believe that the term "driver" (or "LED driver") precludes the possibility that it may be a constant-voltage source. If people followed your view and 'advice' and, when they needed a constant-current source for a string of LEDs, simply asked for an "LED driver", they could (witness the 230,000 Google hits) be legitimately offered a constant-voltage power supply ("constant voltage LED driver").

As I said, people need to be educated to understand what information they need to (AC/DC, constant-voltage or constant-current, and the magnitude of that 'constant' voltage or current) - and that, contrary to what you seem to believe (and believe to be 'correct') that merely asking for a "driver" does not mean that they will only be offered constant-current products.

Kind Regards, John

 

[bernardgreen]

However, what may confuse some is that you now appear to be talking about "a driver driving a driver".

NO I was talking about a power supply supplying power to a driver.

When driver A is used to supply power to driver B ( driver B being the driver connected to the LED elements ) then driver A will raise it's output voltage to a level that ensures the current being forced into driver B is the rated drive current of driver A.

This can and does frequently overvolt the input to driver B It is pot luck how long if at all driver B survives having a supply voltage that is higher than it's input voltage range.

 

[JohnW2]

NO I was talking about a power supply supplying power to a driver.

I know you were, but that doesn't alter my belief that you would probably be confusing some people.

When driver A is used to supply power to driver B ( driver B being the driver connected to the LED elements ) then driver A will raise it's output voltage to a level that ensures the current being forced into driver B is the rated drive current of driver A.

That's only true for those (like you) who have got it into their heads that, despite the decades during which this hasn't been the case, a "driver" is now necessarily a constant-current source. In what you now write, "driver A" would hopefully not "raise its output voltage to level that ensures ...." if it were a constant-voltage driver (like those 230,000 examples that Google found).

This can and does frequently overvolt the input to driver B It is pot luck how long if at all driver B survives having a supply voltage that is higher than it's input voltage range.

Indeed, which is why it is very important that people know and understand whether what they need for their particular purpose is a constant-current 'driver' or a constant-voltage 'driver'.

Kind Regards, John

 

[ericmark]

I see the problem with drivers, but question is about brightness, and in university we did some experiments over driving but switching off/on so average power still within rating of the LED.

We perceived the light as being brighter, but could not measure it as being brighter, as the measuring device took an average.

We also realised over driving causes the LED to go dimmer, and it does not recover, plus problems with photo sensitive disorders.

So better if LED's are under driven.

But lights in general need to be placed a distance apart depending on height mounted and brightness of the lamp, so with a 25 foot ceiling 250 watt low bay lights may work well, but useless with a 10 foot ceiling.

So fitting low output LED lamps under the kitchen cupboards to light the counter may work, but same lights at ceiling height likely useless.

The main problem however is the guy is not in the UK, so saying B&Q or any other outlet have what you need is useless.

And we as electricians don't select a SMS5050 chip or what ever they are called, we select a package, that Includes any dropper resistors and current limiting capacitor, PWM or SMPS used to drive the chip.

I have shown pictures of my lights, but nothing on the strip or paperwork with them says what chip is used, so I can say Lidi units brighter than IKEA, but since these outlets do not supply to where he lives, rather pointless.

 

[JohnW2]

... so I can say Lidi units brighter than IKEA, but since these outlets do not supply to where he lives, rather pointless.

see (here) ....

. I haven't hunted through all the products, but there are items like ...

Kind Regards, John

 

[bernardgreen]

At this rate a PP3 battery fitted in an LED torch will soon be described as a driver ( constant voltage )

 

[ericmark]

The first post in the thread shows a 10 meter coil of LED lights with lumens: 800-850 Lm/Ft, and 72 LED's per meter, with no reference to watts used, states it uses Smd2835 chips and SMD 3014 chips depending where you read, so 22 LED's per foot, with a 20 mA chip which runs at around 3 - 3.5 volt so 1.3 to 1.5 watts per foot or 43 to 50 watt per 10 meter length, if no power wasted.

In the UK most the rope lights I have seen seem to be extra low voltage, this one is 220 volt,

• What Will Your Get ?
• 1x LED Rope Light
• 1x 220V Power Plug

This is very different to UK, but the big question is the control gear, will not call it a driver, we seem to have got stuck on that, but the control gear will use some power, both as a tube and a rope, typically an LED is around 110 lumen per watt, but by time the control gear is added can be down to 65 lumen per watt.

The other question is how accurate is Lumen? Idea is Lumen reflects what the human eye sees, and I found this in practice did not pan out, I started with a living room with 2 bulbs, fitted chandeliers so went to 6 bulbs then 10 bulbs, and over the years went from 2 x 100 watt tungsten, 6 x 40 watt tungsten, 6 x 11 watt CFL, 10 x 8 watt CFL, 10 x 3 watt LED, and finally 10 x 5 watt LED. Looking at lumen output the 10 x 8 watt CFL was the highest, but in real terms very poor lighting, and in real terms the 10 x 5 watt LED gave best general lighting however looking at light at corners of the room, likely the 2 x 100 watt tungsten was best.

I know I made an error using low bay lights with a 8 foot ceiling height. Fluorescent worked far better, it is down to the spread as well as the lumen output, which is why so often the GU10 lights fail, with a simple fluorescent tube the light is reflected from the white ceiling and the area of the tube is greater.

My kitchen counters extend either side of the cooker, the light to the right under the cupboards failed first, and a LED lamp was used to replace it, the light to left failed latter and a lighting strip was used.

With an empty work top you can hardly see the difference, but once you get all my wife's clutter, (hope she never sees this) the spread with the strip lights is clearly better to left than the concentrated single lamp to the right, however since my wife only uses it as a storage area, both lamps are wasted. It seems it is on her to do list.

But distance to object to be illuminated and spread of light is important, as is if the light itself causes a distraction, or causes the eye to reduce light input, if I had switched on the cooker hood lights then the dark area would have been as bright as the rest, however now I have seen the Jaffa Cakes I need to return and remove/digest them!

 

[JohnW2]

At this rate a PP3 battery fitted in an LED torch will soon be described as a driver ( constant voltage )

Who knows, but that would be inconsistent with the use of the word over over past decades.

I really have to doubt the wisdom of the view you are presenting, since it goes beyond semantics, and I fear it could potentially lead to expensive mistakes. Even if you were right in saying that it is "incorrect" to use the term 'driver' for a constant-voltage source, there are so many constant-voltage sources described as 'LED drivers' that a belief that 'drivers' were always constant-current would be unhelpful and misleading. Even reputable manufacturers (e.g Aurora and Knightsbridge, as below) sell things they call "LED drivers" which are constant-voltage.

I certainly agree that it is a minefield for the 'unknowing' but I believe that *(regardless of one's view about 'correct terminology') they need to be taught that there are two types of 'LED drivers' widely available in the marketplace, constant-voltage and constant-current ones, and that it is crucial get the right type (to suit their 'lighting') and then get one with the appropriate output voltage or current.

Kind Regards, John

 

[ericmark]

I seem to remember with aircraft ground lights it was important that they all had same output so the pilot can judge distance, so they used current to voltage transformers all transformers wired in series, seem to remember these were called driver transformers, but it was a long time ago when I worked on the building on mount pleasant airport on the Falklands and it was not my job, only heard other electricians talking.

It has always been a problem finding the right word, I remember working in Algeria where we had the Chevy 4x4's we called them the Blazer but we had a whole range and the parts book was in American English, so you looked at a track rod, scratched your head, and think what would they call this, oh yes a push pull bar.

OK we know hood and trunk but is seems our English has evolved but the English in our old colonial out posts has not, the old songs has changed meanings, there was a jolly miller once, lived on the banks of Dee. It continues using words which have clearly changed meaning.

We have it with "Low Voltage" where USA has a different meaning to ISO, and in spite of ISO not recognising the cm we still teach it in schools. As to writing or typing turning into texting spell check still shows it as being miss spelt.

We know we have to read the spec, the name is just a word used in a word search, we need to check the power, voltage, current, and frequency of any power supply, it really does not matter if called a transformer, driver, ballast, module, or power supply, we read the spec, and anyone who does not is asking for problems.

The real problem is when the advert does not give the spec, or gets it wrong. this is a good example no frequency given, and it says dimmable, low voltage lighting transformer, it is clearly extra low voltage not low voltage, it does not say leading or lagging or recommend a dimming switch to work with it. But it is very clear to anyone reading the advert the output is no over 50 volt AC, is clearly states 11.5 volt.

 

[bernardgreen]

Series Circuit Isolating Transformers

https://www.atgairports.com/wp-content/uploads/2017/03/Series_Circuit_Isolating_Transformers.pdf

 

[Harry Bloomfield]

Series Circuit Isolating Transformers

https://www.atgairports.com/wp-content/uploads/2017/03/Series_Circuit_Isolating_Transformers.pdf

Must admit, I have never come across that principle before.

 

[bernardgreen]

Must admit, I have never come across that principle before.

When the ratio of turns primary/secondary is 1 / 1 then the current driven through each lamp is the same as the current in the ring

Yes driven as the transformer and the primary current determines how much current flows through the lamp as apposed to the lamp determining how much current it will take from the supply.

The voltage across the ends of the ring can be in the thousands of volts on a very long runway.

 

[ericmark]

Only ever seen it at airports. A runway can be up to 2.5 miles long, the is a long distance to run cables without the lamps being effected by volt drop.

I remember some one forgot a cable, in mount pleasant the idea was at the flick of a switch the whole of the complex could be put into darkness, and all lights were powered through a contactor/relay and while the complex was being built the unit was held closed by a lump of cardboard which would be removed as each contactor/relay was wired into the control tower controls.

When it came to testing no lights went out, so electricians sent out to work out why, it seems the contract to run the cable control tower to complex had never been awarded, so the cable did no exist, however now there was a runway between the control tower and the complex, I am sure it was solved and it all works now, but when error was found it caused quite a stir.

I must admit the PSA did it seem have a sense of humour, the street names where bristol helicopters went from was called Eric Ave, and where the police station was called letsbe Ave. Which caused me a problem, stopped by police on way to airport in UK, asked for licence, Oh I said in my luggage, do I really need to get it now, answer you can produce to any British police station, OK I say I will produce it in the Falklands. British is the answer. Are you saying the Falklands is not British I say, well they say you need to give the address Oh that's easy The Police Station, Letsbe Ave., Mount Pleasant, Falkland Islands. To which I get and my name is Donald duck.

They decided they did not need to see licence, and I was allowed to continue, but touch and go for a time.