12V LED downlighter transformer question

[Vortex3]

In my home I have about 20, 20 Watt Halogen downlighters all with MR16/GU5.3
lamps. I want to reduce my energy consumption so these have to be replaced
with something more efficient

Over the past year I have purchased a few sample LED alternatives, but until
historically these have proved to have completely inadequate light output.
In fact absolutely pathetic in many cases.

Last month I finally identified a candidate LED lamp replacement, that is
genuinely bright enough for the job but only about 3W power consumption..
In fact pretty impressive. (ebay 130328613774 for more info), not cheap but
I purchased 4.

I have now encountered the problem that the PSU's in my lighting circuits
won't "start" with a pure LED load. They need to have at least one
incandescent lamp (minimum 20 Watts) to work properly.

Q. Does anybody have experience or opinions on the best 12V transformers
for LED circuits? If so what do I need to look out for?

I see from TLC I can purchase a simple linear transformer like
http://www.tlc-direct.co.uk/Products/TLT50slash1.html which I am sure would
work ...and allow use of a dimmer.

But I also see http://www.tlc-direct.co.uk/Products/LTYT50.html which claims
0-50 Watts. Is there any reason this would NOT work? It's a good price.

Any/all wisdom appreciated.


D

 

[Dave Liquorice]

In fact pretty impressive. (ebay 130328613774 for more info), not cheap
but I purchased 4.

£54.15 to save 68W. Say 10p per kWhr, £54.15 buys you 541,500Whrs at
68W that's 7963hrs, 331 days with the lamps *never* switched off.

Assuming that these are only on during the evening for say 6hrs then
you are looking at over 3 1/2 years to break even assuming they are
on *every* evening for 6hrs.

This doesn't factor in the cost of replacing halogen bulbs over the
expected life of the LED replacement, which will reduce the payback
time. However the ebay description is a bit inconsistent on the
expected life of the LED bulb, 35khrs or 50khrs?

To me it's borderline economic sense. The cost and number of halogens
required over the life of the LED would be the determining factor not
the power saving.

I see from TLC I can purchase a simple linear transformer like
http://www.tlc-direct.co.uk/Products/TLT50slash1.html which I am sure
would work ...and allow use of a dimmer.

I see in the description on ebay:

"Note: LED bulbs should not be used with dimmer switches."

 

[[email protected]]

If you look at the spec for an electronic LV lighting transformer it
usually gives a minimum load.

The 12v LED lamps in Lidl last week stated that they were unsuitable for
electronic transformers.
The last time I tried one with an electronic transformer it just flashed at
about 10 Hz.

 

[NT]

In my home I have about 20, 20 Watt Halogen downlighters all with MR16/GU5.3
lamps.  I want to reduce my energy consumption so these have to be replaced
with something more efficient

Over the past year I have purchased a few sample LED alternatives, but until
historically these have proved to have completely inadequate light output..
In fact absolutely pathetic in many cases.

Last month I finally identified a candidate LED lamp replacement, that is
genuinely bright enough for the job but only about 3W power consumption..
In fact pretty impressive. (ebay 130328613774 for more info),  not cheap but
I purchased 4.

I have now encountered the problem that the PSU's in my lighting circuits
won't "start" with a pure LED load.   They need to have at least one
incandescent lamp (minimum 20 Watts) to work properly.

Q.   Does anybody have experience or opinions on the best 12V transformers
for LED circuits?  If so what do I need to look out for?

I see from TLC I can purchase a simple linear transformer likehttp://www.tlc-direct.co.uk/Products/TLT50slash1.htmlwhich I am sure would
work ...and allow use of a dimmer.

But I also seehttp://www.tlc-direct.co.uk/Products/LTYT50.htmlwhich claims
0-50 Watts.  Is there any reason this would NOT work?  It's a good price.

Any/all wisdom appreciated.

D

Use a toroidal transformer. Or you might have a square 12v ac
transformer sitting in your junkbox.


NT

 

[Vortex4]

In fact pretty impressive. (ebay 130328613774 for more info), not cheap
but I purchased 4.

£54.15 to save 68W. Say 10p per kWhr, £54.15 buys you 541,500Whrs at
68W that's 7963hrs, 331 days with the lamps *never* switched off.

Assuming that these are only on during the evening for say 6hrs then
you are looking at over 3 1/2 years to break even assuming they are
on *every* evening for 6hrs.

This doesn't factor in the cost of replacing halogen bulbs over the
expected life of the LED replacement, which will reduce the payback
time. However the ebay description is a bit inconsistent on the
expected life of the LED bulb, 35khrs or 50khrs?

To me it's borderline economic sense. The cost and number of halogens
required over the life of the LED would be the determining factor not
the power saving.

I see from TLC I can purchase a simple linear transformer like
http://www.tlc-direct.co.uk/Products/TLT50slash1.html which I am sure
would work ...and allow use of a dimmer.

I see in the description on ebay:

"Note: LED bulbs should not be used with dimmer switches."

--
Cheers
Dave.

I calculated 4 years. based on year-round average of 4-6 hours per day
usage.

I expect to live in my house for another 10+ years.

Honestly it's a "no brainer" but I accept these lamps wiill become cheaper
over time and don't forget energy prices will go up.

 

[Vortex4]

Typical LV electronic transformers have a minimum load that needs to be
connected before they work correctly. If you look at the OPs second link
you will note that is *not* a typical electronic transformer, and claims
to work from zero load up to its maximum.

I just ordered one to try it out!

Seems to be a pretty popular make and model but nowhere on t'interweb is LED
suitability mentioned....so I will adopt the empirical approach.

 

[Rob G]

In my home I have about 20, 20 Watt Halogen downlighters all with MR16/GU5.3
lamps.  I want to reduce my energy consumption so these have to be replaced
with something more efficient

Over the past year I have purchased a few sample LED alternatives, but until
historically these have proved to have completely inadequate light output..
In fact absolutely pathetic in many cases.

Last month I finally identified a candidate LED lamp replacement, that is
genuinely bright enough for the job but only about 3W power consumption..
In fact pretty impressive. (ebay 130328613774 for more info),  not cheap but
I purchased 4.

I have now encountered the problem that the PSU's in my lighting circuits
won't "start" with a pure LED load.   They need to have at least one
incandescent lamp (minimum 20 Watts) to work properly.

Q.   Does anybody have experience or opinions on the best 12V transformers
for LED circuits?  If so what do I need to look out for?

I see from TLC I can purchase a simple linear transformer likehttp://www.tlc-direct.co.uk/Products/TLT50slash1.htmlwhich I am sure would
work ...and allow use of a dimmer.

But I also seehttp://www.tlc-direct.co.uk/Products/LTYT50.htmlwhich claims
0-50 Watts.  Is there any reason this would NOT work?  It's a good price.

Any/all wisdom appreciated.

D

Interesting. Anyone any idea how these bulbs are configured ?

One option (are there others?) - 12v supply and one diode voltage of
say 2 v suggests 8 banks of 6 diodes in series, with 26ma therefore
passing through each bank. The design of these diodes must have come
a long way to produce that amount of light from 26ma / diode.

What happens when one diode fails - does the whole bank go out, or
will they be like xmas tree lights and have some bypass system when a
bulb fails ? I notice that LED traffic lights fail in blocks.

Rob

 

[Rob G]

Interesting.  Anyone any idea how these bulbs are configured ?

One option (are there others?) - 12v supply and one diode voltage of
say 2 v suggests 8 banks of 6 diodes in series, with 26ma therefore
passing through each bank.  The design of these diodes must have come
a long way to produce that amount of light from 26ma / diode.

What happens when one diode fails - does the whole bank go out, or
will they be like xmas tree lights and have some bypass system when a
bulb fails ?  I notice that LED traffic lights fail in blocks.

Rob

I went off to look at bulb outputs, and found this website

http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mr16/performance.asp

The measurements are for 50w bulbs so it would seem that the 240
lumens claimed is pretty good and hence meets Vortex's subjective
measurement.

One of the interesting things is that halogen MR16 have been measured
at the centre of the beam which is much narrower than the 120 degrees
from the LED ones. If indeed these LED bulbs are subjectively good
with this much wider beam then it does look as if things are going in
the right direction.

Rob

 

[Andrew Gabriel]

I went off to look at bulb outputs, and found this website
http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mr16/performance.asp
The measurements are for 50w bulbs so it would seem that the 240
lumens claimed is pretty good and hence meets Vortex's subjective
measurement.
One of the interesting things is that halogen MR16 have been measured
at the centre of the beam which is much narrower than the 120 degrees
from the LED ones. If indeed these LED bulbs are subjectively good
with this much wider beam then it does look as if things are going in
the right direction.

Note that lumens is the total light output from a lamp summed
in all directions. (In theory, it's measured by using what's
called an "Integrating Sphere", which sums the light output
in all directions to calculate the total lumen output.)
So the lumen output is unaffected by things like beam angle.
Intensity of a beam is candella (which is effectively lumens
per solid angle, i.e. within a cone) and intensity of a lit
surface is lux (which is effectively lumens per area).

Many of the LED lights around have quite high intensity beams,
but an extremely small solid angle, so the total lumen output
is tiny. That's why they look bright when you stare back up
the beam, but don't manage to light up anything much bigger
than an ant crawling directly under them on the floor, never
mind a whole room.

 

[Vortex3]

Many of the LED lights around have quite high intensity beams,
but an extremely small solid angle, so the total lumen output
is tiny. That's why they look bright when you stare back up
the beam, but don't manage to light up anything much bigger
than an ant crawling directly under them on the floor, never
mind a whole room.

These LED lamps use SMD components without lenses so are not very
directional compared to traditional LED's, but there is less light loss
because of the lack of lenses and also less heating. Lower junction
temperature means more light. Positive things.

They are "warm white" which is achieved by using a yellowish filter, this
does cost some brightness....and cause additional heating. I've not tried
the "daylight white" ones yet. I suspect they take a little getting used
to.

From ceiling height a tratitional halogen GU10 delivers an intense pool of
light about 2' diameter at counter level. Tweaking 3 of them to
illuminate - say - a breakfast bar is a bit of a compromise. IMHO these LED
lights are much less directional.

D

 

[stan]

These LED lamps use SMD components without lenses so are not very
directional compared to traditional LED's, but there is less light loss
because of the lack of lenses and also less heating.  Lower junction
temperature means more light.  Positive things.

They are "warm white" which is achieved by using a yellowish filter, this
does cost some brightness....and cause additional heating.  I've not tried
the "daylight white" ones yet.  I suspect they take a little getting used
to.

From ceiling height a tratitional halogen GU10 delivers an intense pool of
light about 2' diameter at counter level.  Tweaking 3 of them to
illuminate - say - a breakfast bar is a bit of a compromise.  IMHO these LED
lights are much less directional.

D

Who could have anticipated that 'lighting', could get so complicated!
What with LV starting circuits, LED and transformers, halogen down
lighters etc. etc.!
Interesting though.
Here, for the moment sticking with plain old 115/120 volt
incandescents, costing about 25 cents Canadian (about 14 new pence)
each, in packages of four. Nice simple technology.
The wasted lamp heat, now that temps have dropped below 12 degrees C
(about 50 deg F) at night just aiding the electric heating, along with
wasted heat from the TV etc. until we go to bed.
Oddly the only bulb that failed in any spectacular manner was a 230
volt low wattage that I brought back (new) from the middle east, and
placed above the work bench to monitor the 230 volt feed (115 plus
115) for some 230 volt tool/items there.
It 'went off' with quite flash and tripped a 30 amp breaker!
In workshop/garage we have quite a supply of used four foot, two and
four tube fluorescent fixtures. Some are not cosmetically perfect but
clean up well and work fine even in low temperatures. Also have a back
up supply of used ballasts and tubes so can also keep neighbours
fixtures supplied. Main fluorescent string fixtures in downstairs
workshop have 'electronic ballasts' and are from a school
refurbishing. They were just chucking em out; so went in and asked if
could take a few. Their only question was "Can you take all of them;
save us a trip to the dump/tip?". Seek and you shall find; I guess.

 

[Appin]

The message
<[email protected]m>

Here, for the moment sticking with plain old 115/120 volt
incandescents, costing about 25 cents Canadian (about 14 new pence)
each, in packages of four. Nice simple technology.

That'll be at the usual ration of one 60w bulb per room?

(Traditioinal Canadian practice with a four-lamp ceiling fixture with
only one bulb inserted with the result that Stygian gloom pervades the
room)