Re: Circuit Design Q. - battery charger
- From: Kris Krieger <me@xxxxxxxxxx>
- Date: Sat, 12 Jul 2008 16:13:00 -0500
RHRRC <h.lewis@xxxxxxxxxxxxxxx> wrote in
news:fd69cfee-a98d-43a8-85d2-487d7c551e83@xxxxxxxxxxxxxxxxxxxxxxxxxxx:
On 9 Jul, 21:42, Kris Krieger <m...@xxxxxxxxxx> wrote:[snihttp://www.goldmine-elec-products.com/prodinfo.asp?
number=G16642/edited]
If anyone knows of a better LED, I'd be interested in the mfgr and
designation so I can look into it.
Once again, many thanks in advance for answers, suggestions,
information, references, and so on :) !
- Kris Krieger
Lots of questions there but just to start with one of them:
The led you quote are typically 18000mCd @ 20mA.
With their angle (2*theta1/2) of 15 deg this would calc to a bit under
1 lumen. The forward voltage is ~3.4V @ 20mA giving 68mW for 0.98
lumen or about 14.4 lumen per watt.
Although they may be more watty animals than you require the latest
offerings from Lumileds, Cree, Seoul Semi and the like are 70 lumen
per watt and upwards - 100 lumen per watt binning being offered -at a
price- in production quantities.
All the work in white leds is in the 1 and higher wattage devices and
it may be that the 5mm led marker is being ignored but I would look
for a more efficacious led if you can.
Regards
Hi and thanks!; - I'm trying to find the Math, but I'm confused - when the
specs say that an LED delivers X Lumens, tha's not really true...?
I found one resource that said One Candela = 12.57 Lumens", but then I
found another source taht said, "A 25,000mcd LED produces 25 lumens" *but*
that it translates into *actually* being only 2.39 lumens"...<?>
....and what does it mean when an incandescent light bulb package says, for
example, "800 lumens"? I know how to translate that into a compact
fluorescent light bulb, but with LEDs, it seems that sometimes Lumens means
one thing, but other times it means something completely different.
So, from that, all I can figure is that using, for example, six 11,000mcd
LEDs with the same 20 deg viewing angle as the above reference 25,000mcd
LED), that should translate into only about 6.3 lumens, despite the one
source that siad 1000mcd translates into 12.57lumens...??
The more I read, the more confused I get. It'd be nice if there was some
online calcualtor that let you put in mcd value and viewing angle, and
output the near equivalnet in terms of an incandescent light bulb -
especially given that "lumens" actually has different meanings...
So I'm left wondering how to evaluate the following:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=67-2027-ND
5MM WHITE, 11000mcd, 20deg viewing angle, 3.5V, 20mA, 8000K
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16642
"Brilliant white LED is our brightest. This LED contains
5 chips inside a crystal clear 10mm LENS. It produces a
color temperature of 7000K and has a luminous intensity
of 265,000MCD. The DC forward voltage is 3.4V to 3.8VDC,
DC forward current 100mA and viewing angle is 40º. Chip
material is InGaN and reverse voltage is 5.0Volts."
Similar:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16659
" Warm White LED contains 5 chips inside a crystal
clear 10mm lens. This is a warm white output color
3000K-4000K (more like an incandescent light). Specs
VF 3.8V, IV=200,000 to 220,000MCD, viewing angle 45º,
PD=500mW, IF=100mA. This beautiful high output LED
glows almost a pale yellow at 3VDC and changes to
bright warm white glow at 3.5VDC."
It'd be nice if there was some sort of definitive reference...
TIA,
- Kris
.
- References:
- Circuit Design Q. - battery charger
- From: Kris Krieger
- Re: Circuit Design Q. - battery charger
- From: RHRRC
- Circuit Design Q. - battery charger
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