Brian Gaff (Sofa) wrote

Where is this day which is over 24 hours long though?

I keep it here and no, you can't use it.

Half the issue is often the heat, but I'd have thought in a normal
installation they would be designed to have an acceptable life under such
conditions, otherwise where do you draw the line?

At lending you my very useful day.

"Theo" wrote in message
...
Roland Perry wrote:
I've got GU10 LED downlighters in my extension, supplied by the
builder's subcontractor (so a bit arm's length).

So far, about 8 months later, four of the twelve have failed. They start
flickering for a few days, then go very dim. On about 12hrs a day.

Contacted the supplier (Meridian) who wouldn't comment on how long they
were supposed to last [see below], but sent me two replacements.

The box says "2yrs Guarantee", which is 34hrs a day at the "average
life" of 25k hrs.

If the MTBF is 25k hours that means some proportion of them are going to
fail before 25k hours. If that was a median TBF it would be half of
them.
But they've run about 3k hours, so it's hard to think of a distribution
where a third of them would have failed at that point.

I suppose this is the hazard of fitting lights with unreplaceable lamps -
it
only takes one of them to die to make the rest of the installation look
bad.

Theo

On Mon, 15 Feb 2021 03:58:50 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

FLUSH the trolling senile cretin's latest troll**** unread

--
Marland addressing senile Rodent's tall stories:
"Do you really think people believe your stories you come up with to boost
your self esteem."
Message-ID:

In message , at 06:41:12 on Sun, 14 Feb 2021,
Roland Perry remarked:
In message , at 14:29:18 on Sat, 13 Feb
2021, Martin Brown remarked:
On 13/02/2021 11:29, Roland Perry wrote:
I've got GU10 LED downlighters in my extension, supplied by the
builder's subcontractor (so a bit arm's length).

Simple question is how warm are the bulbs when one has been left on
for a few hours? That almost invariably will explain the shortened life.

When I changed the 4th one the other day, the main part was OK but the
base stub was almost too hot to hold.

If it is too warm to touch then it is almost certainly drying out its
PSU capacitors which will result in premature failure. Electrolytics
and heat do not get on. It might be worth your while taking it apart
to check how it has failed (as I recall you are an electronics engineer).

I'll do that (although it's more like mechanical engineering ;-)

Remarkably few components. Yes, there's an old-fashioned electrolytic
capacitor (4.7uF), plus the two-legged "red blob", four surface mount
resistors and one surface-mount ?transistor.

http://www.perry.co.uk/images/gu10.jpg

My money is definitely on capacitors that don't any more. The other
common one I have seen is single point failure on one LED die in a
series string but that doesn't do the PSU flashing thing.

So far, about 8 months later, four of the twelve have failed. They
start flickering for a few days, then go very dim. On about 12hrs a

Contacted the supplier (Meridian) who wouldn't comment on how long
they were supposed to last [see below], but sent me two replacements.
The box says "2yrs Guarantee", which is 34hrs a day at the "average
life" of 25k hrs.

They are good for the rated hours if they are able to dissipate away
their waste heat but downlighters in ceilings tend not to be able to
do that.

The original insulated fireproof fittings intended for running very
hot quartz halogen downlighters are particularly bad for killing LED
bulbs.

I'll take a look at a fitting later, and report back.

A dull metal cylinder about the size of a baked bean tin, with a few
very small holes at the top, but nothing at all to introduce any
convection currents either lower down, or around the LED itself.
--
Roland Perry

On 14/02/2021 12:53, John Rumm wrote:
On 13/02/2021 17:06, Pancho wrote:
On 13/02/2021 14:21, Harry Bloomfield wrote:
After serious thinking Pancho wrote :
Halogens give out 10 times as much heat. They need to have cooling
for the bulb. Sure the equilibrium temperature for a 50W halogen may
be much greater than a 5W LED would tolerate. But the equilibrium
temperature for a 5W bulb will be much, much lower. I will leave one
on for a couple of hours and measure the temp.

Even 5w generates an awful lot of waste heat, so far as the
electronics of LED's are concerned. I prefer electronics to run 50C,
their life is reduced at much above 70C. Really, the cooler running
the better.

After 2 hours on the GU10 case was about 58C, at its hottest point,
measured with a laser thermometer. I dunno what that implies about the
internal temp.

It will likely be a bit hotter - so running very close to, or over the
maximum temperature for many budget capacitors.



I accept in theory, in some circumstances, GU10 downlights can have a
limited lifespan compared to an integral version.

However the the reliability benefits of Integral really would have to be
quite large to justify them.

I know they are easy to change, but many people can change a light bulb
but not an integral fitting. So if one did go wrong the cost would be
very large compared to £1.50 to replace a GU10 bulb.

Also I like daylight bulbs, a lot of people don't, with GU10s it is a
few minutes to swap the whole house.

I can't help but think if heating is a problem there are better
solutions than integral fittings.

Roland Perry wrote:
In message , at 06:41:12 on Sun, 14 Feb 2021,
Roland Perry remarked:
In message , at 14:29:18 on Sat, 13 Feb
2021, Martin Brown remarked:
On 13/02/2021 11:29, Roland Perry wrote:
I've got GU10 LED downlighters in my extension, supplied by the
builder's subcontractor (so a bit arm's length).

Simple question is how warm are the bulbs when one has been left on
for a few hours? That almost invariably will explain the shortened life.

When I changed the 4th one the other day, the main part was OK but the
base stub was almost too hot to hold.

If it is too warm to touch then it is almost certainly drying out its
PSU capacitors which will result in premature failure. Electrolytics
and heat do not get on. It might be worth your while taking it apart
to check how it has failed (as I recall you are an electronics
engineer).

I'll do that (although it's more like mechanical engineering ;-)

Remarkably few components. Yes, there's an old-fashioned electrolytic
capacitor (4.7uF), plus the two-legged "red blob", four surface mount
resistors and one surface-mount ?transistor.

http://www.perry.co.uk/images/gu10.jpg

That might be a capacitor dropper. Capacitor droppers are
a potential solution on low wattage bulbs.

https://bobparadiso.files.wordpress....p_dropper2.png

More sophisticated ones are protected a bit against overvoltage.

But regular designs like that, they do not take kindly to
transients on AC supply. A brief transient can cause the
light to "flash" brightly in sympathy, and excess currents
in the LEDs, lead to their demise. I'm not sure what would
cause a "flickering fault" in such a setup - the main dropper
cap (polypropylene?) has most of the drop across it.

Paul

"Paul" wrote in message
...
Roland Perry wrote:
In message , at 06:41:12 on Sun, 14 Feb 2021,
Roland Perry remarked:
In message , at 14:29:18 on Sat, 13 Feb
2021, Martin Brown remarked:
On 13/02/2021 11:29, Roland Perry wrote:
I've got GU10 LED downlighters in my extension, supplied by the
builder's subcontractor (so a bit arm's length).

Simple question is how warm are the bulbs when one has been left on for
a few hours? That almost invariably will explain the shortened life.

When I changed the 4th one the other day, the main part was OK but the
base stub was almost too hot to hold.

If it is too warm to touch then it is almost certainly drying out its
PSU capacitors which will result in premature failure. Electrolytics
and heat do not get on. It might be worth your while taking it apart to
check how it has failed (as I recall you are an electronics engineer).

I'll do that (although it's more like mechanical engineering ;-)

Remarkably few components. Yes, there's an old-fashioned electrolytic
capacitor (4.7uF), plus the two-legged "red blob", four surface mount
resistors and one surface-mount ?transistor.

http://www.perry.co.uk/images/gu10.jpg

That might be a capacitor dropper. Capacitor droppers are
a potential solution on low wattage bulbs.

https://bobparadiso.files.wordpress....p_dropper2.png

More sophisticated ones are protected a bit against overvoltage.

But regular designs like that, they do not take kindly to
transients on AC supply. A brief transient can cause the
light to "flash" brightly in sympathy, and excess currents
in the LEDs, lead to their demise.

But a regulated current should survive that fine.

I'm not sure what would cause a "flickering fault" in such a setup - the
main dropper cap (polypropylene?) has most of the drop across it.

Yeah,it would be interesting to measure one with that fault.

Paul

On 14/02/2021 09:03, Brian Gaff (Sofa) wrote:
So, how hot do they get? Does seem to me that they have not been designed
with a typical use condition in the first place.

Get a 1W rated resistor and dissipate 1W through it and see how hot it
gets.


In this case the size of the bulb and the type of fitting are the
problem. The LED equivalent bulbs have not been designed from new but as
a replacement to fit in an existing fitting. The only physical
connections are two lugs for the electrical supply and therefore cannot
be optimised for maximum heat sinking. This coupled with their small
size and usually in housings that fully enclose the bulb (apart from the
front) makes getting rid of unwanted heat from the bulb difficult.



What actually fails, I
wonder. Do they have a psu or is it strictly diodes and some kind of over
voltage protection with them all in series?

Both LEDs and power supplies fail if they get too hot. In the very small
bulbs there may be a couple of capacitors, a bridge rectifier and a few
resistors all packed into a space much smaller than the top of your
little finger. Often one of the capacitors is an electrolytic type.

In panel type lights that have been designed for LEDS. the LEDS are
bolted directly to some metal-work. In many of the ones that I've
fitted there has been been a substantial metal backplate.

In outside flood light fittings the LED designs are completely different
from the previous halogen models. The LEDs are bolted directly to the
metal housing which provides the heat-sink.



--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 14/02/2021 08:58, Brian Gaff (Sofa) wrote:
Where is this day which is over 24 hours long though?


Half the issue is often the heat, but I'd have thought in a normal
installation they would be designed to have an acceptable life under such
conditions, otherwise where do you draw the line?

Existing fittings are designed for different operating conditions. They
are designed to survive high operating temperatures and not necessarily
to cool the bulb.

Downlighters designed for LEDs don't have replaceable bulbs! This is how
adequate heat-sinking is achieved because the LED can be in physical
contact with the metal of the fitting. It also allows the power supply
electronics to be removed away from the LEDs so one is not necessarily
directly heating the other.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 14/02/2021 17:57, Pancho wrote:

I can't help but think if heating is a problem there are better
solutions than integral fittings.

Yes, don't use fitting with such small bulbs.



--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 14/02/2021 17:36, Roland Perry wrote:

Remarkably few components. Yes, there's an old-fashioned electrolytic
capacitor (4.7uF), plus the two-legged "red blob", four surface mount
resistors and one surface-mount ?transistor.

http://www.perry.co.uk/images/gu10.jpg


Capacitor dropper (red blob), bridge rectifier (not transistor) ,
smoothing capacitor (4.7uF, rated at 105 degrees C) and resistors acting
as fuses, inrush current limiters and bleeds.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

In article , Roland Perry
writes
In message , at
12:04:27 on Sat, 13 Feb 2021, John Rumm
remarked:
On 13/02/2021 11:40, Theo wrote:
Roland Perry wrote:
I've got GU10 LED downlighters in my extension, supplied by the
builder's subcontractor (so a bit arm's length).

So far, about 8 months later, four of the twelve have failed. They start
flickering for a few days, then go very dim. On about 12hrs a day.

Contacted the supplier (Meridian) who wouldn't comment on how long they
were supposed to last [see below], but sent me two replacements.

The box says "2yrs Guarantee", which is 34hrs a day at the "average
life" of 25k hrs.
If the MTBF is 25k hours that means some proportion of them are
going to
fail before 25k hours. If that was a median TBF it would be half of them.
But they've run about 3k hours, so it's hard to think of a distribution
where a third of them would have failed at that point.
I suppose this is the hazard of fitting lights with unreplaceable
lamps - it
only takes one of them to die to make the rest of the installation look
bad.

GU10 suggests replaceable lamps rather than permanent ones.

That's right - theyare easily replaced.

The usual problem with LED lamps is their ability to shed heat, and
that is heavily dictated by the enclosure. Many GU10 fittings will
leave the lamp completely exposed - and one would expect that to give
adequate cooling. Fully enclosed in a downlighter - especially if
covered in insulation could result in much higher run temperatures and
so dramatically shorter life expectancy.

Being in the ceiling of an extension they are very well insulated to
the side and above.
I had the same issue with our extension. So up in the loft I carefully
created a space in the insulation around each fitting. Then when
boarding over I cut a circular hole over each bulb to allow the heat to
rise. Covered the hole with mesh to prevent the inevitable.
--
bert