Guest
On Feb 21, 10:14 am, "Dave" <db5...@hotmail.com> wrote:
of time relative to what you end up with. The more partially if not
wholly finished parts you dig up, the less time and expertise it will
require. You might want to look at the various bits and pieces at one
of the sites I mentioned previously, see if they give you any ideas.
http://www.dealextreme.com/products.dx/category.917
be nearly as bright at 12V, and while I'm sure somebody makes 18V
bulbs they're quite a bit rarer than 12V, limiting your choices and/or
raising cost, plus a good result over this operational voltage range
would require a regulated supply. I would think about using an LED
for this too, with optics or a reflector, or both, for the tighter
beam you're probably seeking.
Previously it was 4 x AA, presumably something like the following
might've worked (though it's spotlight probably uses a lower powered,
less bright LED than the LEDs I was previously writing about),
http://www.batterykings.com/energizer-double-bright---includes-4-aa-batteries--flashlights-batteries-bb-000400.html
but now 18V? Was this an RC toy or drill battery? It seems a big
jump in voltage compared to the small handheld flashlights I thought
we were talking about. If you want 18V the solution is easier, get a
ready-made flashlight that comes as close as possible to your needs
from a hardware store, something made for cordless drills. When they
have a fluorescent tube in them they tend not to have the incandescent
spotlight too, or vice-versa, but if you're wanting an 18V light I
doubt the end use will be the same as what I was envisioning
previously.
taking at least a dozen hours and maybe $75 or more. Seems like a
great length to go to, to reinvent the wheel when there are so many
flashlights out in the market.
unreasonably laborious and expensive to end up with a flashlight.
It'll end up costing multiple times as much as a finished product, be
no more reliable (except maybe the switch if you use a good quality
one), and will use a battery pack that already has wear on it when a
finished new product may come with a brand new pack.
To DIY, I would not use a buck regulator (letalone linear, it'd be far
too lossy/large a heatsink) to go down to 12VD then back up to 120V,
instead you'd want a rare 18VDC to ~ 120VAC booster. Well I wrote
rarer but here's the irony: The best place to find one of those is to
buy a finished cordless drill pack compatible 18V flashlight then take
the driver board out of it, but it seems a bit backwards when it's a
whole finished flashlight already.
http://www.mytoolplace.net/Hitachi-14.4V-18V-Cordless-Lantern-Light/M/B000MGEKGM.htm
http://cgi.ebay.com/DeWalt-18Volt-Fluorescent-Area-Light-DC527-Cordless-18v_W0QQitemZ140300371671QQcmdZViewItem
(or just buy the whole kit with battery and charger, then you're 100%
set).
IF you just wanted to throw this together cheap, you could just put 4
of these in series on your 18V pack, then calculate out a suitable
current limiting resistor for the series. I prefer proper LED drivers
but they start costing a lot more if in an odd voltage like 18V, or
maybe even higher peak voltage if that is spec'd as an 18V rechargable
pack?
wouldn't need external switching transistors, would have it
integrated), study the datasheet, refer to the examples and calculate
out the support parts' specs you need to get from point a to b.
Generally you'd be looking at an IC that has an internal reference
voltage that is compared against a small drop across a minimal value
resistor, to regulate the current through the load (LEDs). So you'd
typically have up to a half dozen small heat resistant capacitors,
fewer resistors, an inductor, plus the board/wires/connectors/etc.
so long as you don't pick a terribly lossy way to drive them like a
linear regulator or dropping too much with a series resistor, and
don't overdrive them very excessively, instead adding more LEDs
instead of more current per LED. A single 3W LED driven at that (3W),
will be brighter than the typical krypton flashlight bulb, but there
are so many sizes, shapes, ratings for a bulb it really depends on
exactly what you're comparing to, and for the intended use you'll have
to pick the best optics or reflector.
possible. Either buy a finished product that comes closest to your
needs, or mount about 4 Cree XR-E on a piece of 1" square aluminum
tubing (about 3/32" or thicker walled) and give them 500 to 750mA in
series off your 18V pack. See how that looks, and if the tubing stays
cool enough for the application. LEDs are fun to play around with, at
worst if you don't think they're suitable there's bound to be
something else you can put them in, like a different flashlight,
undercabinet lighting, automotive use, or something similar.
True, even trying to recreate a $2 plastic 2D flashlight takes a lot
of time relative to what you end up with. The more partially if not
wholly finished parts you dig up, the less time and expertise it will
require. You might want to look at the various bits and pieces at one
of the sites I mentioned previously, see if they give you any ideas.
http://www.dealextreme.com/products.dx/category.917
Depends on what "in some fashion" means, a bulb optimal for 18V won't
be nearly as bright at 12V, and while I'm sure somebody makes 18V
bulbs they're quite a bit rarer than 12V, limiting your choices and/or
raising cost, plus a good result over this operational voltage range
would require a regulated supply. I would think about using an LED
for this too, with optics or a reflector, or both, for the tighter
beam you're probably seeking.
Previously it was 4 x AA, presumably something like the following
might've worked (though it's spotlight probably uses a lower powered,
less bright LED than the LEDs I was previously writing about),
http://www.batterykings.com/energizer-double-bright---includes-4-aa-batteries--flashlights-batteries-bb-000400.html
but now 18V? Was this an RC toy or drill battery? It seems a big
jump in voltage compared to the small handheld flashlights I thought
we were talking about. If you want 18V the solution is easier, get a
ready-made flashlight that comes as close as possible to your needs
from a hardware store, something made for cordless drills. When they
have a fluorescent tube in them they tend not to have the incandescent
spotlight too, or vice-versa, but if you're wanting an 18V light I
doubt the end use will be the same as what I was envisioning
previously.
I could be wrong, but am starting to think this flashlight will end up
taking at least a dozen hours and maybe $75 or more. Seems like a
great length to go to, to reinvent the wheel when there are so many
flashlights out in the market.
In my opinion you have several project targets that make it
unreasonably laborious and expensive to end up with a flashlight.
It'll end up costing multiple times as much as a finished product, be
no more reliable (except maybe the switch if you use a good quality
one), and will use a battery pack that already has wear on it when a
finished new product may come with a brand new pack.
To DIY, I would not use a buck regulator (letalone linear, it'd be far
too lossy/large a heatsink) to go down to 12VD then back up to 120V,
instead you'd want a rare 18VDC to ~ 120VAC booster. Well I wrote
rarer but here's the irony: The best place to find one of those is to
buy a finished cordless drill pack compatible 18V flashlight then take
the driver board out of it, but it seems a bit backwards when it's a
whole finished flashlight already.
http://www.mytoolplace.net/Hitachi-14.4V-18V-Cordless-Lantern-Light/M/B000MGEKGM.htm
http://cgi.ebay.com/DeWalt-18Volt-Fluorescent-Area-Light-DC527-Cordless-18v_W0QQitemZ140300371671QQcmdZViewItem
(or just buy the whole kit with battery and charger, then you're 100%
set).
Up to 3W, driven lower they have higher efficiency.
IF you just wanted to throw this together cheap, you could just put 4
of these in series on your 18V pack, then calculate out a suitable
current limiting resistor for the series. I prefer proper LED drivers
but they start costing a lot more if in an odd voltage like 18V, or
maybe even higher peak voltage if that is spec'd as an 18V rechargable
pack?
Same as any other circuit? Pick a driver IC (which for this load
wouldn't need external switching transistors, would have it
integrated), study the datasheet, refer to the examples and calculate
out the support parts' specs you need to get from point a to b.
Generally you'd be looking at an IC that has an internal reference
voltage that is compared against a small drop across a minimal value
resistor, to regulate the current through the load (LEDs). So you'd
typically have up to a half dozen small heat resistant capacitors,
fewer resistors, an inductor, plus the board/wires/connectors/etc.
LEDs will be multiple times brighter at any current drain you select,
so long as you don't pick a terribly lossy way to drive them like a
linear regulator or dropping too much with a series resistor, and
don't overdrive them very excessively, instead adding more LEDs
instead of more current per LED. A single 3W LED driven at that (3W),
will be brighter than the typical krypton flashlight bulb, but there
are so many sizes, shapes, ratings for a bulb it really depends on
exactly what you're comparing to, and for the intended use you'll have
to pick the best optics or reflector.
I would pick one of two paths trying to meet all goals as much as
possible. Either buy a finished product that comes closest to your
needs, or mount about 4 Cree XR-E on a piece of 1" square aluminum
tubing (about 3/32" or thicker walled) and give them 500 to 750mA in
series off your 18V pack. See how that looks, and if the tubing stays
cool enough for the application. LEDs are fun to play around with, at
worst if you don't think they're suitable there's bound to be
something else you can put them in, like a different flashlight,
undercabinet lighting, automotive use, or something similar.
