Re: Circuit Design Q. - battery charger

Hi Kris and all.

On Jul 10, 10:42 am, Kris Krieger <m...@xxxxxxxxxx> wrote:
RHRRC <h.le...@xxxxxxxxxxxxxxx> wrote innews:fd69cfee-a98d-43a8-85d2-487d7c551e83@xxxxxxxxxxxxxxxxxxxxxxxxxxx:

On 9 Jul, 21:42, Kris Krieger <m...@xxxxxxxxxx> wrote:

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

Thanks for the info :) I've been having a bit of trouble with LEDs
because for some, the specifications list lux, others list watts, others
list mcd, or "lambert", or so on - I'm still very new at all of this, so
I've been having trouble translating "watts" into "mcd (and lumens since
1000mcd=12.57 lumens)", but your info gives me a better understanding,
thanks!

So I'll go ahead and look into more and different LEDs, and look for some
additional generalized "LED tech" info as well - I didn't realize that the
angle was so closely related to the actual light output; I'd assumed that
it was teh same amount of lighting, just "squished" into a narrower beam,
so I'm glad to know that's incorrect *before* putting it all together ;)

I'll visit the websites for the companies you mentioned, and look around
for others producing sinmilar LEDs.

Thanks again :)
- Kris

Since your involved in product developement, it might
be a good idea to test them personally. The LEDs are
vital to the product and the choice is a "subjective"
thing as well as an efficiency decision. You could
likely get free samples, but the cost is minimal in
the greater scheme of things ;-).
Of course from the current and voltage you can find
the power (watts).
Regards
Ken
.

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