'Cree LED lamp'
For our resident LED man
cdb, btech-online.co.uk on 21/10/2011 colin
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> For our resident LED man
Always good to see such news - keep it coming.
That's an 8.7 Watt "bulb"
Redefining what is possible with high-performance LED lighting, the
lamp delivers more than 1,300 lumen at 152 lumen per watt (LPW) using
Cree TrueWhite® Technology.
That's impressive, BUT if somebody wanted to pay me enough I could
knock them up something that matched the lumen.Watt of that device,
but not the CRI of 91. And, it would be seriously ugly.
Worse, I could do it using 3+ year old technology that I have on the shelf now.
Mine would use almost 100 small LEDs run at 60% of their rated
current, giving typically 160 l/W+ .
Very non cost effective compared to their, and I'd love to have what
they use inside to play with, but it's also surprising how far they
I presently get a whole 15 lumen at about 125-135 l/W OUT as certified
by an international test house (who may or may not know their stuff)
and that's after passing through a flat polycarbonate lens- good for
about 8% loss. So over 140 l/W running them above optimal efficiency.
Strip off the lens and reduce the current per LED and ... .
That's low voltage DC feed BUT Cree did not say if the unit was AC or
DC fed and the way these things work, if it too was DC lv feed none
would be surprised.
Applied Technology ltd
|On Fri, Oct 21, 2011 at 12:29 PM, RussellMc <gmail.com> wrote: apptechnz
> That's impressive, BUT if somebody wanted to pay me enough I could
> knock them up something that matched the lumen.Watt of that device,
> but not the CRI of 91. And, it would be seriously ugly.
> Worse, I could do it using 3+ year old technology that I have on the shelf now.
> Mine would use almost 100 small LEDs run at 60% of their rated
> current, giving typically 160 l/W+ .
> Very non cost effective compared to their, and I'd love to have what
> they use inside to play with, but it's also surprising how far they
> haven't come.
But isn't the whole point the CRI, the form factor and the cost? After
all I'm sure they could get significantly higher lm/W if they used
twice as many cold white LEDs and decreased the power supplied to
each. Personally I'm impressed we're still seeing significant advances
- not like we'll ever again have the overnight 100% increase in
efficiency when the XR-E was released.
How would you handle cooling with your 100 LED array? I'm guessing
it's not something you have to worry about too much with a single LED
running at ~30mA.
> But isn't the whole point the CRI,
CRI is a point as is CCT (2800k specified).
I hate 2800k compared to higher temperature colours.
5600k is fine by me.
Thy seem to think people want to live in Tungsten lit rooms.
I'd rather live in daylight like lit rooms.
My LEDs have a CCT of about 6000k and a CRI of low (have to check
report but was under 70 I think). BUT it's a lovely shade - most
people like it and it has a nice "feel". Whatever.
> the form factor
Cree seem to have allowed themselves to dispense with conventional
form factor. A choice I approve of. I've been thinking along those
lines just recently.
> and the cost?
I don't think they mentioned cost :-).
> all I'm sure they could get significantly higher lm/W if they used
> twice as many cold white LEDs and decreased the power supplied to
They are limited to the CCT specified by the advanced standard. And
they may have used more LEDs run at low % of output to achieve what
they did. Or not.
> Personally I'm impressed we're still seeing significant advances
> - not like we'll ever again have the overnight 100% increase in
> efficiency when the XR-E was released.
That was only a quantum leap wrt prior offerings they had. My 3+ year
old Nichias are still up wit XR-E's when derated. But at a very small
fraction of the power !. (100 mW/LED)
> How would you handle cooling with your 100 LED array? I'm guessing
> it's not something you have to worry about too much with a single LED
> running at ~30mA.
One LED is "not hard" - although you do actually see the difference
between 1 LED done well and 3 of the same done stupidly by a factory
when you weren't looking against explicit instructions to the contrary
and then formally tested over 2000 hours by an important certifying
authority :-). Fortunately the sheer brilliance of the LED (pun almost
unintended) is more than a match for the stupidity of the factory. The
1 LED improves in output by 1 to 2 % over 2000 hours. The 3 identical
LEDS drop by a fraction of a % over 2000 hours. The latter result
would be highly acceptable if it were not for what could have been
LEDs are 100 mW and 7mm on a side . If you stack them (example only)
on say 7.5mm grid a square array = 75mm x 75mm = 3" square. You then
have 10 Watts to dissipate less the not insignificant light radiation
:-) - small portion but actually noticeable.
Take a single prepreg layer (0.25mm) and copper to suit and laminate
onto finned block of Aluminum of your choosing. A few degrees C per
Watt will be acceptable. Fan blow if challenge is too hard. Else
convection/radiation cool with eg liquid filling to get heat out onto
an outer surface or heat pipe or ... if you wish. ie it's not
conceptually hard - just a matter of finding some existing engineering
method that works for you. I have several hundred of these LEDs. One
day ... ;-).
Applied technology ltd.
On Fri, Oct 21, 2011 at 7:29 AM, RussellMc <gmail.com> wrote: apptechnz
> Always good to see such news - keep it coming.
I happened to be in wal*mart the other day and I was shocked at the
amount shelf space dedicated to LED lighting. Looking a little more
closely, I noticed that the LED slighting shelves were fully stocked
all the way to the back of the shelving units. The shelving rack with
the generic wal*mart incandescent bulbs was completely empty except
for three packages of 40 watt bulbs.
Assuming that wal*mart does not have supply chain issues, I believe
that cost and public opinion are going to be major issues here. The
quality control issues of CFLs seems to have strongly turned people
off from anything other than incandescent bulbs.
|At 11:48 AM 10/21/2011, Peter Johansson wrote:
>Assuming that wal*mart does not have supply chain issues, I believe
>that cost and public opinion are going to be major issues here. The
>quality control issues of CFLs seems to have strongly turned people
>off from anything other than incandescent bulbs.
Gosh - I'm not aware of quality issues with CFL lamps. I guess that I should do some Googling, but can you give me any pointers as to where to look?
I'm responsible for having installed several hundred CFL lamps in various households (mine, friends, family) over the past 7 or 8 years and all appear to be working well - and for very long periods of time.
I've got a small collection of bulbs that I've collected as they have failed but the failure rate is astonishingly low. Most of the failures are the bulb itself (black bands near where the glass exits the base). The electronics appear to be fine on almost every lamp that I have disassembled.
My favorite bulbs were made by Noma (purchased at Canadian Tire) but they don't stock them anymore. Luckily, I have a stockpile of several dozen in 9W and 13W.
I should mention that our power supply is 120Vac, 60Hz. That might have a bearing on failure rates.
-- Dwayne Reid <planet.eon.net> dwayner
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Custom Electronics Design and Manufacturing
On Fri, Oct 21, 2011 at 3:23 PM, RussellMc <gmail.com> wrote: apptechnz
>> and the cost?
> I don't think they mentioned cost :-).
Though you seem to think that your solution wouldn't be cost effective
compared to theirs (I'd have suggested it otherwise!)
>> Personally I'm impressed we're still seeing significant advances
>> - not like we'll ever again have the overnight 100% increase in
>> efficiency when the XR-E was released.
> That was only a quantum leap wrt prior offerings they had. My 3+ year
> old Nichias are still up wit XR-E's when derated. But at a very small
> fraction of the power !. (100 mW/LED)
It was a quantum leap wrt any comparable high power LED made by
anybody. How do your Nichias compare to a derated XR-E (ISTR those
become far more efficient when run at very low power)?
> >> and the cost?
> > I don't think they mentioned cost :-).
> Though you seem to think that your solution wouldn't be cost effective
> compared to theirs (I'd have suggested it otherwise!)
I know that my LEDs are not cost competitive Watt per Watt with XRE's
or any modern high Wattage white LED as mine are very low wattage and
cost does not, alas, scale down linearly with Wattage. So I'd
certainly hope that anything new was more cost effective than using 3+
year old Nichia 100 m,W LEDs. I' d need 100 x NSPWR70CSS-K1 at say
around 50 cents each or $50 of LED's. An XR-E in true production
volumes is probably about $1.50 so you'd hope a new 10W source of 1 to
3 LEDs will be say $5 and falling when it arrives as a real product.
> >> Personally I'm impressed we're still seeing significant advances ....
> > That was only a quantum leap wrt prior offerings they had. My 3+ year ....
> It was a quantum leap wrt any comparable high power LED made by
> anybody. How do your Nichias compare to a derated XR-E (ISTR those
> become far more efficient when run at very low power)?
Short: Surprisingly well given their age.
Lonnnnng: There are two data-sheet factors that govern l/W efficiency.
These are not primary factors in their own right - just visible
indicators of the deep underlying magic.
- One is a relatively slight kink in the close to straight line lumen
per mA curve. This is close to the form of y = kX with a very slight
kink towards Y = k.X^(1-1/N) where N is largish (flu on Y axis,
current on axis). For most purposes you read this as "if I double he
current I don't quite get double the lumens" but it works backwards
when candlepower is the aim.
- The greater factor is the forward voltage with current curve which
is a classic exponential curve. As you increase current through say
10% to 100% of rate value you get modest increases in Vf - say from
2.9V to 3.3V, corresponding at constant lumen per mA to a loss of
efficiency by a factor of 2.9/3.3 =~ 12% in this example. Of interest
is the shape of the curve and the absolute vaklue of Vf at rated
current. With improving LED technology VF operating is dropping. Most
LEDs have a substantial spread of production Vf values leading to a
wide binning range of l/W values. My Nichia Raijins cluster immensely
impressively around Vf = 2.95 V at whatever reference current they
used. (I have a Nichia report based on large volume sampling from
production. Results slowly get better with time). Few modern white
LEDs are getting down to that Vf to start, so far.
Manufacturers don't usually expect you to run an LED at 5% or 10% of
it's rated Wattage. eg an about 5 Watt capable XR-E at 500 mW or less.
So hard data is not usually offered so you need to either ask (and may
be told) or blow up datasheet graphs immensely and try to plot data
from them in a manner not probably intended. At lower levels these
are liable to not be intended as definitive and are also only typical
values. BUT I have in fact done this for the XR-E a while ago and it
looks good but not stunning wrt the Raijin.
Raijin gives 160+ l/W at 30 mA. It was originally a 30 m rated part
but Nichia appear to have decided that it was so good that they rated
it at 50 mA (it's in a P4 7mm 4-lead through hole package) and
provided decreased lifetime figure to match. From memory it's 14,000
hours to 70% at 50 mA. (Actual measured as noted is +1% to +2%
increase in output at 2000 hours at about 45 mA :-).
XR-E gives > 160 l/W at say 10% rated power but not so vastly better
than Raijin as to make your eyes water. (Do not stare into beam with
For some reason, 3+ years ago Nichia made an utterly stunning small
LED, packaged it strangely (P4 only, no SMD), did not match it with an
SMD equivalent, did not come close to matching it with a higher power
version, and then they and everyone else waited several years to
finally catch it up. They have now done so, but not stunningly so.
There will shortlyish be new products around which compete in a
similar application area but so far at the lower power levels it's
still the best.
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