Harbor Freight 4 LED $7.00

H

Henry Kolesnik

Guest
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to beleive
they are direct wired. Looking inside as best I can it looks like all 4 are
in parallel and connect directly to the 3 cells in series. I think LEDs are
supposed draw a lot less current if they have a dropping resistor. I'm
guessing that a dropping resistor would reduce current draw substantially,
increase led life and not reduce light output significantly. But I can see
were I could easliy install a resistor. I also know just about zero on
leds.
tnx

--

73
Hank WD5JFR
 
"Henry Kolesnik" <kolesnik@sbcglobal.net> writes:
I think LEDs are
supposed draw a lot less current if they have a dropping resistor.
Click to expand...
LEDs have a more or less fixed forward voltage drop. If you supply more
voltage than that to them, they draw more current (and produce more
light). But beyond a certain amount of current, they will be damaged.

I'd be surprised if the flashlight has no current limiting resistor.

I'm guessing that a dropping resistor would reduce current draw
substantially, increase led life and not reduce light output
significantly. But I can see
were I could easliy install a resistor.
Click to expand...
Light output is nearly a linear function of current. If you increase
the resistance, you will decrease the current, and hence the
light output. This will increase the LED life, but the life was
probably good enough already.
 
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to beleive
they are direct wired. Looking inside as best I can it looks like all 4 are
in parallel and connect directly to the 3 cells in series. I think LEDs are
supposed draw a lot less current if they have a dropping resistor. I'm
guessing that a dropping resistor would reduce current draw substantially,
increase led life and not reduce light output significantly. But I can see
were I could easliy install a resistor. I also know just about zero on
leds.
Click to expand...
Sounds like they are using the battery internal resistance to limit the
current. Four LEDs at 30mA/ea gets your ~120mA with Vbatt pulled down to
maybe 3.5V at that current. And it probably has a "good enough" graceful
degradation with battery run down causing the current to taper off
exponentially after a point-reducing battery discharge per use. It does
require the LEDs to be matched to some degree.
 
"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:8ovje.1965$wb2.1791@newssvr11.news.prodigy.com...
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to
beleive
they are direct wired. Looking inside as best I can it looks like all
4 are
in parallel and connect directly to the 3 cells in series. I think
LEDs are
supposed draw a lot less current if they have a dropping resistor.
I'm
guessing that a dropping resistor would reduce current draw
substantially,
increase led life and not reduce light output significantly. But I
can see
were I could easliy install a resistor. I also know just about zero
on
leds.
tnx
Click to expand...
Seems like everything is made for the flashlight that has the profile of
the Mini-Maglite. It has two cells, and fits into all sorts of
holsters, pockets, carriers, etc. So if you get it, or a similarly
sized flashlight, then you're home free. Of course the Mini Maglite has
a halogen bulb, so it sucks. I bought the MagmaLED and Opalec Newbeam
conversion kits for mine, and I'm happy with them. I've seen the three
cell flashlights and I would much prefer that mine not be that long,
three cells is just too long.

Dorcy sells some four LED, two cell flashlights, for under $16. I
bought a couple and They work but the rubber gtrips fall off - no big
thing.

One other disappointing thing about three cells lights is that if they
are direct connected, then you can't use Ni-MH rechargeables in them.
Some flashlights with the V boost circuitry can run on Ni-MHs, possibly
at reduced light output.

--
73
Hank WD5JFR
Click to expand...
 
On 20 May 2005 17:48:55 -0700, the renowned Eric Smith
<eric@brouhaha.com> wrote:

"Henry Kolesnik" <kolesnik@sbcglobal.net> writes:
I think LEDs are
supposed draw a lot less current if they have a dropping resistor.

LEDs have a more or less fixed forward voltage drop. If you supply more
voltage than that to them, they draw more current (and produce more
light). But beyond a certain amount of current, they will be damaged.

I'd be surprised if the flashlight has no current limiting resistor.
Click to expand...
It's fairly common that it doesn't.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
On Sat, 21 May 2005 00:36:20 GMT, "Henry Kolesnik"
<kolesnik@sbcglobal.net> wrote:

I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to beleive
they are direct wired. Looking inside as best I can it looks like all 4 are
in parallel and connect directly to the 3 cells in series. I think LEDs are
supposed draw a lot less current if they have a dropping resistor. I'm
guessing that a dropping resistor would reduce current draw substantially,
increase led life and not reduce light output significantly. But I can see
were I could easliy install a resistor. I also know just about zero on
leds.
tnx
Click to expand...
I would assume that LEDs that are now made for flashlights have
built in pulse circuitry to get the brightest output from the
LED. They would include what is necessary to operate at the
correct voltage.
 
"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:ps8t815qkhgumi6kdh7gl5890rnsffbouo@4ax.com...
On 20 May 2005 17:48:55 -0700, the renowned Eric Smith
eric@brouhaha.com> wrote:

"Henry Kolesnik" <kolesnik@sbcglobal.net> writes:
I think LEDs are
supposed draw a lot less current if they have a dropping resistor.

LEDs have a more or less fixed forward voltage drop. If you supply
more
voltage than that to them, they draw more current (and produce more
light). But beyond a certain amount of current, they will be
damaged.

I'd be surprised if the flashlight has no current limiting resistor.

It's fairly common that it doesn't.


Best regards,
Spehro Pefhany
--
Click to expand...
I agree. The ones that I've seen without a resistor are mostly the ones
that use a CR2016 or CR2025 button cell, basically those keychain lights
that you squeeze. The cells have enough internal resistance to limit
the current.

But alkaline AA cells are capable of delivering more than an amp. I
don't know what the internal resistance is, but it's very low. The
multiple LED Altoids box lights that I've built use 33 ohm resistors,
and I've put as many as 8 LEDs on a set of 3 AA cells, and they're
_bright_. More commonly I do 6 LEDs, each with a 33 ohm resistor, and I
consider that a minimum for a decent source of light.

By using 4 LEDs and no resistors, the light output is probably greater
than my 6 LED lights, but from what I've seen over just a few hundred
hours, the light output from these flashlights will drop off after only
a few hundred hours or less when pushed to this high a current. But it
may take more than a year and several sets of AA cells to put a hundred
hours on a flashlight, and by that time, the warranty has expired.
:-( This is a dirty little secret that no flashlight maker wants you to
know.
 
"Si Ballenger" <shb*NO*SPAM*@comporium.net> wrote in message
news:428ebd92.864194966@news.comporium.net...
On Sat, 21 May 2005 00:36:20 GMT, "Henry Kolesnik"
kolesnik@sbcglobal.net> wrote:

I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to
beleive
they are direct wired. Looking inside as best I can it looks like
all 4 are
in parallel and connect directly to the 3 cells in series. I think
LEDs are
supposed draw a lot less current if they have a dropping resistor.
I'm
guessing that a dropping resistor would reduce current draw
substantially,
increase led life and not reduce light output significantly. But I
can see
were I could easliy install a resistor. I also know just about zero
on
leds.
tnx

I would assume that LEDs that are now made for flashlights have
built in pulse circuitry to get the brightest output from the
LED. They would include what is necessary to operate at the
correct voltage.
Click to expand...
Your assumptions are wrong.
 
"Henry Kolesnik" <kolesnik@sbcglobal.net> schreef in bericht
news:8ovje.1965$wb2.1791@newssvr11.news.prodigy.com...
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to beleive
they are direct wired. Looking inside as best I can it looks like all 4
are in parallel and connect directly to the 3 cells in series. I think
LEDs are supposed draw a lot less current if they have a dropping resistor.
I'm guessing that a dropping resistor would reduce current draw
substantially, increase led life and not reduce light output significantly.
But I can see were I could easliy install a resistor. I also know just
about zero on leds.
tnx

--

73
Hank WD5JFR
Click to expand...
Hank,

Adding a resistor will not be that difficult. A thin piece of two sided PCB
and some handiwork with a fret-saw and a fraise will do the trick. As AA is
pretty small you may need to use two or more SMD resistors in parallel. The
round piece of PCB should be place between a battery and its press spring.

petrus bitbyter
 
"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in
message news:428f0f95$0$157$3a628fcd@reader2.nntp.hccnet.nl...
"Henry Kolesnik" <kolesnik@sbcglobal.net> schreef in bericht
news:8ovje.1965$wb2.1791@newssvr11.news.prodigy.com...
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to
beleive
they are direct wired. Looking inside as best I can it looks like
all 4
are in parallel and connect directly to the 3 cells in series. I
think
LEDs are supposed draw a lot less current if they have a dropping
resistor.
I'm guessing that a dropping resistor would reduce current draw
substantially, increase led life and not reduce light output
significantly.
But I can see were I could easliy install a resistor. I also know
just
about zero on leds.
tnx
73
Hank WD5JFR

Hank,

Adding a resistor will not be that difficult. A thin piece of two
sided PCB
and some handiwork with a fret-saw and a fraise will do the trick. As
AA is
pretty small you may need to use two or more SMD resistors in
parallel. The
round piece of PCB should be place between a battery and its press
spring.
Click to expand...

My dictionary says a fraise is "an obstacle of pointed stakes driven
into the ramparts of a fortification in a horizontal or inclined
position".
Which I don't think is what you had in mind. Maybe you could explain.
Thanks.

> petrus bitbyter
 
On Sat, 21 May 2005 05:49:09 -0700, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

Adding a resistor will not be that difficult. A thin piece of two
sided PCB
and some handiwork with a fret-saw and a fraise will do the trick. As
AA is
pretty small you may need to use two or more SMD resistors in
parallel. The
round piece of PCB should be place between a battery and its press
spring.

My dictionary says a fraise is "an obstacle of pointed stakes driven
into the ramparts of a fortification in a horizontal or inclined
position".
Which I don't think is what you had in mind. Maybe you could explain.
Thanks.
Click to expand...
He clearly means a strawberry.

d

Pearce Consulting
http://www.pearce.uk.com
 
On Sat, 21 May 2005 01:00:14 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

"Si Ballenger" <shb*NO*SPAM*@comporium.net> wrote in message
news:428ebd92.864194966@news.comporium.net...
On Sat, 21 May 2005 00:36:20 GMT, "Henry Kolesnik"
kolesnik@sbcglobal.net> wrote:

I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to
beleive
they are direct wired. Looking inside as best I can it looks like
all 4 are
in parallel and connect directly to the 3 cells in series. I think
LEDs are
supposed draw a lot less current if they have a dropping resistor.
I'm
guessing that a dropping resistor would reduce current draw
substantially,
increase led life and not reduce light output significantly. But I
can see
were I could easliy install a resistor. I also know just about zero
on
leds.
tnx

I would assume that LEDs that are now made for flashlights have
built in pulse circuitry to get the brightest output from the
LED. They would include what is necessary to operate at the
correct voltage.

Your assumptions are wrong.
Click to expand...
And your proof is...? ;-)
 
On Sat, 21 May 2005 05:49:09 -0700, the renowned "Watson A.Name -
\"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in
message news:428f0f95$0$157$3a628fcd@reader2.nntp.hccnet.nl...

"Henry Kolesnik" <kolesnik@sbcglobal.net> schreef in bericht
news:8ovje.1965$wb2.1791@newssvr11.news.prodigy.com...
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to
beleive
they are direct wired. Looking inside as best I can it looks like
all 4
are in parallel and connect directly to the 3 cells in series. I
think
LEDs are supposed draw a lot less current if they have a dropping
resistor.
I'm guessing that a dropping resistor would reduce current draw
substantially, increase led life and not reduce light output
significantly.
But I can see were I could easliy install a resistor. I also know
just
about zero on leds.
tnx
73
Hank WD5JFR

Hank,

Adding a resistor will not be that difficult. A thin piece of two
sided PCB
and some handiwork with a fret-saw and a fraise will do the trick. As
AA is
pretty small you may need to use two or more SMD resistors in
parallel. The
round piece of PCB should be place between a battery and its press
spring.

My dictionary says a fraise is "an obstacle of pointed stakes driven
into the ramparts of a fortification in a horizontal or inclined
position".
Which I don't think is what you had in mind. Maybe you could explain.
Thanks.
Click to expand...
A google search comes up with "fraise toestel", but it's not clear to
me what exactly it does. Cut a donut in the PCB?


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
On Fri, 20 May 2005 22:57:44 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wroth:

On 20 May 2005 17:48:55 -0700, the renowned Eric Smith
eric@brouhaha.com> wrote:

"Henry Kolesnik" <kolesnik@sbcglobal.net> writes:
I think LEDs are
supposed draw a lot less current if they have a dropping resistor.

LEDs have a more or less fixed forward voltage drop. If you supply more
voltage than that to them, they draw more current (and produce more
light). But beyond a certain amount of current, they will be damaged.

I'd be surprised if the flashlight has no current limiting resistor.

It's fairly common that it doesn't.
Click to expand...
If you think about it, the batteries do have an equivalent series
resistance and the LEDs are not perfect voltage clamps either. There IS a
series resistance even though there is no discrete resistor in the circuit.

Jim
 
On Sat, 21 May 2005 15:03:39 GMT, the renowned James Meyer
<jmeyer@nowhere.net> wrote:

On Fri, 20 May 2005 22:57:44 -0400, Spehro Pefhany
speffSNIP@interlogDOTyou.knowwhat> wroth:

On 20 May 2005 17:48:55 -0700, the renowned Eric Smith
eric@brouhaha.com> wrote:

"Henry Kolesnik" <kolesnik@sbcglobal.net> writes:
I think LEDs are
supposed draw a lot less current if they have a dropping resistor.

LEDs have a more or less fixed forward voltage drop. If you supply more
voltage than that to them, they draw more current (and produce more
light). But beyond a certain amount of current, they will be damaged.

I'd be surprised if the flashlight has no current limiting resistor.

It's fairly common that it doesn't.


If you think about it, the batteries do have an equivalent series
resistance and the LEDs are not perfect voltage clamps either. There IS a
series resistance even though there is no discrete resistor in the circuit.

Jim
Click to expand...
Exactly. That's why they work. Maybe not as perfectly as some would
like, but good enough to sell.

OTOH, an LED backlit LCD graphics display I have uses some
sophisticated white LED driver chip arrangement. The backlight snaps
on as the voltage is ramped up, almost like a fluorescent.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
On Sat, 21 May 2005 10:39:40 -0400, Spehro Pefhany wrote:
On Sat, 21 May 2005 05:49:09 -0700, the renowned "Watson A.Name -
\"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:
"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in
"Henry Kolesnik" <kolesnik@sbcglobal.net> schreef in bericht
I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to
beleive
they are direct wired. Looking inside as best I can it looks like
all 4
are in parallel and connect directly to the 3 cells in series. I
think
LEDs are supposed draw a lot less current if they have a dropping
resistor.
I'm guessing that a dropping resistor would reduce current draw
substantially, increase led life and not reduce light output
significantly.
But I can see were I could easliy install a resistor. I also know
just
about zero on leds.

Adding a resistor will not be that difficult. A thin piece of two
sided PCB
and some handiwork with a fret-saw and a fraise will do the trick. As
AA is
pretty small you may need to use two or more SMD resistors in
parallel. The
round piece of PCB should be place between a battery and its press
spring.

My dictionary says a fraise is "an obstacle of pointed stakes driven
into the ramparts of a fortification in a horizontal or inclined
position".
Which I don't think is what you had in mind. Maybe you could explain.
Thanks.

A google search comes up with "fraise toestel", but it's not clear to
me what exactly it does. Cut a donut in the PCB?

Heck, I'm still stuck on 'fret-saw'. )-;
Click to expand...

Thanks,
Rich
 
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com>
schreef in bericht news:118ubhriv1mi152@corp.supernews.com...
"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in
message news:428f0f95$0$157$3a628fcd@reader2.nntp.hccnet.nl...


Adding a resistor will not be that difficult. A thin piece of two
sided PCB
and some handiwork with a fret-saw and a fraise will do the trick. As
AA is
pretty small you may need to use two or more SMD resistors in
parallel. The
round piece of PCB should be place between a battery and its press
spring.

My dictionary says a fraise is "an obstacle of pointed stakes driven
into the ramparts of a fortification in a horizontal or inclined
position".
Which I don't think is what you had in mind. Maybe you could explain.
Thanks.
Click to expand...
Milling cutter. (Dutch -> Frees).

--
Thanks, Frank.
(remove 'q' and 'invalid' when replying by email)
 
Don Pearce wrote:

On Sat, 21 May 2005 05:49:09 -0700, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:


Adding a resistor will not be that difficult. A thin piece of two

sided PCB

and some handiwork with a fret-saw and a fraise will do the trick. As

AA is

pretty small you may need to use two or more SMD resistors in

parallel. The

round piece of PCB should be place between a battery and its press

spring.

My dictionary says a fraise is "an obstacle of pointed stakes driven
into the ramparts of a fortification in a horizontal or inclined
position".
Which I don't think is what you had in mind. Maybe you could explain.
Thanks.


He clearly means a strawberry.
Click to expand...
LOL, it is indeed one of the meaning of "fraise" in French. One of the
other ones is "milling cutter", which I guess is a good version.
Source is www.granddictionaire.com, an awesome resource.
 
Si Ballenger wrote:
On Sat, 21 May 2005 01:00:14 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:


"Si Ballenger" <shb*NO*SPAM*@comporium.net> wrote in message
news:428ebd92.864194966@news.comporium.net...

On Sat, 21 May 2005 00:36:20 GMT, "Henry Kolesnik"
kolesnik@sbcglobal.net> wrote:


I just got a 4 white LED flashlight that uses 3 AA cells from Harbor
freight. I measured the current at 127 ma and and that leads me to

beleive

they are direct wired. Looking inside as best I can it looks like

all 4 are

in parallel and connect directly to the 3 cells in series. I think

LEDs are

supposed draw a lot less current if they have a dropping resistor.

I'm

guessing that a dropping resistor would reduce current draw

substantially,

increase led life and not reduce light output significantly. But I

can see

were I could easliy install a resistor. I also know just about zero

on

leds.
tnx

I would assume that LEDs that are now made for flashlights have
built in pulse circuitry to get the brightest output from the
LED. They would include what is necessary to operate at the
correct voltage.

Your assumptions are wrong.


And your proof is...? ;-)
Click to expand...
Watson *knows* LEDs. You might want to do a little
research - perhaps find a flashlight with a LED such
as you describe - before trying to challenge him.

Personally, I have never owned, seen or heard of a
flashlight that uses an LED where the LED includes what
is necessary to operate at the correct voltage.

Ed
 
If you think about it, the batteries do have an equivalent series
resistance and the LEDs are not perfect voltage clamps either. There IS a
series resistance even though there is no discrete resistor in the circuit.

Jim


Exactly. That's why they work. Maybe not as perfectly as some would
like, but good enough to sell.
Click to expand...
There is much more to it than that- parallel LEDs are more reliable than
any other configuration and putting the full battery voltage across the
LEDs maximizes sensitivity of current to battery voltage so that when
the user notices less than satisfactory light output he/she still has
ample use remaining to change out the batteries- sort of like the low
gas level warning on the car dashboard.
 
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