On Mon, 10 Nov 2003 23:23:12 -0500, No1 wrote:
On Thu, 16 Oct 2003 01:22:36 GMT, Gunner wrote:
On Wed, 15 Oct 2003 14:52:10 -0500, Bob Robinson
wrote:
AL A. wrote:
Hi all,
I know this is not strictly on topic, but this crew seems to know something
about everythig, so here goes:
I am looking to build a "task" lamp (think dentist-type light) that uses
high output white LEDs for a friend who often does
work for extended periods of time in very remote places. I was looking at
the NTE electronics "lightwave" flashlights
http://www.nteinc.com/lightwave/ and they claim that they have circuitry
that makes it possible to run one of the 10
led lights for 24 days, continuously, on 3 D cells.
Any idea how they accomplish that? Most of the high output LEDs I have seen
seem to want to run between 20 and 40 mA
current draw. Given the amp-hour ratings I find for D cells, I don't see how
that would work out. Do they modulate the power to the LEDs
in some way that helps extend the battery life so dramatically?
I looked at just modifing a lightwave flashlight for the task at hand, but
the beam is a bit too wide for what he needs. So I am hoping to
build something with maybe 3 LEDs and appropriate optics to give a fairly
narrow, even beam, mounted on a gooseneck type thing,
with a remote battery pack on a cord.
Any thoughts on the electronics involved? I can handle that part of it, if
I know what I am trying to accomplish.Of course the body
of the thing will be METAL, nicely turned, naturally. (obligatory
metalworking content...)
Thanks for any ideas you can offer.
-AL
AL,
I'm working on a similar project at the moment. Here's what my research
has yielded so far. The majority of ultra bright leds do operate in the
20-40ma range, and the forward voltage is around 1.5-1.7V. If you
arrange the 3 LEDs in series with at least enough cells to provide 4.5V
and an appropriate current-limiting resistor, your current draw will be
20-40ma. If the NTE light is using 7 LEDs with 3 D cells, they are
wiring them in parallel, so the current draw is at least 140ma and the
24 hr figure is highly suspect. If you connect yours in parallel, you
could get by with 2 1.5V cells, but your current draw would triple.
Hope this helps,
Bob
If you folks come up with decent LED flashlights, or plans..the people
over on misc.survivalism would love to have some, as this is a regular
topic of discussion.
Gunner
"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto
Gunner, have a look at mine on http://members.cox.net/ledflashlight
The little two led light work really well, I used them for 4 days during Isabel.
Those cost about $12 in parts but are pretty rugged, you can turn one on and
throw it in your back yard and just go pick it up. They run on a 9 volt battery
or 4 AAA's depending on the dropping resistor. The one shown uses 4 AAA's I get
very good time out of them(usable light)before needing to change a battery. One
nice thing is these lights will fit in the mouth between your teeth , when you
need two hands, without much discomfort and an aluminum type thratens to break
your teeth. I use those particular Led holders because they act as reflectors,
versus just mounting the Led in the raw.
The 10 led job was used, along with the 2 Led versions, during Isabel also and
had been used many many hours befor. I use that one under the truck. The ten Led
flashlight runs on 4 D cells and I have yet to change them in the couple of
months since I built it. I don't know the exact run time.
A note, you wont get blazing bright out of these things, but you get plent of
usable light. Leds are directional and don't "add". If you have ten LEd's
pointing at the same spot then you get brighter light. If the Led's are pointing
straight forward like the ten Led flashlight then you get more light, some gets
brighter because some of the Led's are close enough to add.
No1
MANY thanks, saved for closer review!!!
Gunner
"By calling attention to 'a well regulated militia', the 'security' of the
nation, and the right of each citizen 'to keep and bear arms', our founding
fathers recognized the essentially civilian nature of our economy. Although
it is extremely unlikely that the fears of governmental tyranny which gave
rise to the Second Amendment will ever be a major danger to our nation, the
Amendment still remains an important declaration of our basic
civilian-military relationships, in which every citizen must be ready to
participate in the defense of his country. For that reason, I believe the
Second Amendment will always be important."
-- Senator John F. Kennedy, (D) 1960