The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries. Thats why you never have to shake them when new.

I dismantled one, and found the batteries. I removed the batteries
and they work without the batteries as long as they are shook almost
constantly. They stay on for over an hour after being shook, but the
light is so dim it's useless, and a match is brighter.

Once again we as consumers, are being deceived by the advertisers.

A good buddy bought 2 at the rodgers ohio flea market. You did way
better than he did.

His flashlight worked off those 2 batteries but they went dead, and
shaking didnt work

It turned out the thing that shakes wasnt magnetic, which is needed for
charging and the little board was bad. My buddy is a retired
electronics engineer and found them interesting....

There have een other reports too, from tampa of the complete junk type.

one could put D cells in that unit and with the LEDs small current draw
have light for days.


so you did good at least it wasnt pure junk...

wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

Thats why you never have to shake them when new.

I dismantled one, and found the batteries. I removed the batteries
and they work without the batteries as long as they are shook almost
constantly. They stay on for over an hour after being shook, but the
light is so dim it's useless, and a match is brighter.

Once again we as consumers, are being deceived by the advertisers.

--
Joseph Meehan

Dia duit

"Joseph Meehan" wrote in message
...
wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?


There may be some shake lights made that really work, but the 2 I have seen
taken apart had 2 small batteries in them. The markings on the batteries
were standard battery types. The 'magnets' in them were not even real
magnets. They would not attract any metal.
The lights would burn about a day without shaking and never light again.

Joseph Meehan wrote:
wrote:
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

I took one apart, and the flat disks were large hearing aid batteries.
Both wires from the shaker coil were soldered into the same hole of an
unstuffed PC board which might have charged the batteries charged if
it had been correctly assembled.

Nick

There are some fakes which do run off a couple button cells. Shake
thing is just snake oil advertising.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Joseph Meehan" wrote in message
...
wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

Ralph Mowery wrote:
"Joseph Meehan" wrote in message
...
wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?


There may be some shake lights made that really work, but the 2 I
have seen taken apart had 2 small batteries in them. The markings on
the batteries were standard battery types. The 'magnets' in them
were not even real magnets. They would not attract any metal.
The lights would burn about a day without shaking and never light
again.

I have only seen one and it appeared to be real. The run time varied up
to about 15 minutes after shaking and would come back up when shaken. It
sounds like some of them out there are not the real thing. Frankly I don't
have a lot of interest in the real thing as the battery powered units should
run long enough for any of my uses. I have several battery lights around the
house and they all still work and I don't think I have replaced a battery in
over five years.

--
Joseph Meehan

Dia duit

In the event of a disaster, one of these "shaker" flashlights could come in
handy so I've been exercising so I could keep one running for quite a while.
My wife calls me a pervert. What's with that?

wrote in message
...
Joseph Meehan wrote:
wrote:
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

I took one apart, and the flat disks were large hearing aid batteries.
Both wires from the shaker coil were soldered into the same hole of an
unstuffed PC board which might have charged the batteries charged if
it had been correctly assembled.

Nick

On Fri, 12 May 2006 13:55:05 GMT, "Joseph Meehan"
wrote:

Ralph Mowery wrote:
"Joseph Meehan" wrote in message
...
wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?


There may be some shake lights made that really work, but the 2 I
have seen taken apart had 2 small batteries in them. The markings on
the batteries were standard battery types. The 'magnets' in them
were not even real magnets. They would not attract any metal.
The lights would burn about a day without shaking and never light
again.

I have only seen one and it appeared to be real. The run time varied up
to about 15 minutes after shaking and would come back up when shaken. It
sounds like some of them out there are not the real thing. Frankly I don't
have a lot of interest in the real thing as the battery powered units should
run long enough for any of my uses. I have several battery lights around the
house and they all still work and I don't think I have replaced a battery in
over five years.

I have seen three types of these "genlights".
One is obviously fake as it is powered by two coin cells, has no
magnet and no components on the circuit board. Batteries seem to have
poor capacity.

One has 2 rechargeable cells and does in fact charge the cells when
shaken. It has magnetic slide and board is populated.

One has a large capacitor charged by the shaken magnet. The board is
populated.

May be other types but these three are in the markets. Both the latter
types work fairly well as an emergency light source.
--
Mr.E

On Fri, 12 May 2006 02:01:43 -0500, wrote:

The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries. Thats why you never have to shake them when new.

I dismantled one, and found the batteries. I removed the batteries
and they work without the batteries as long as they are shook almost
constantly. They stay on for over an hour after being shook, but the
light is so dim it's useless, and a match is brighter.

Once again we as consumers, are being deceived by the advertisers.


Were they batteries, as in regular, chemical batteries? Or, are you
calling 'batteries' what could be capacitors to hold voltage/power
inbetween shakes?

later,

tom @ www.BlankHelp.com

Tom The Great wrote:
Were they batteries, as in regular, chemical batteries? Or, are you
calling 'batteries' what could be capacitors to hold voltage/power
inbetween shakes?

They are button cells.

In article , lid writes:

| I have seen three types of these "genlights".
| One is obviously fake as it is powered by two coin cells, has no
| magnet and no components on the circuit board. Batteries seem to have
| poor capacity.
|
| One has 2 rechargeable cells and does in fact charge the cells when
| shaken. It has magnetic slide and board is populated.
|
| One has a large capacitor charged by the shaken magnet. The board is
| populated.
|
| May be other types but these three are in the markets. Both the latter
| types work fairly well as an emergency light source.

Walgreens had a $5 "sale" on these a few weeks ago. There was a whole
shelf full of assorted types, many of which were just broken. Of those
that worked, most were the type with two coin cells. Some, however,
had a single HiMH battery (I'm trusting that they didn't fake the label
on the battery) and a correctly wired bridge rectifier actually connected
to the coil... plus a real magnet. I bought one of these. Of course,
the battery is charged so it's hard to say whether it works. If it
doesn't charge once it runs down maybe I'll try replacing the battery
with a super cap, assuming the coil is indeed putting out voltage.

Dan Lanciani
ddl@danlan.*com

The latest fad has been these flashlights that you shake to charge.

The electrical energy available from that much shaking is insufficient to
charge a battery or run a flashlight. The ones I've seen such as at Wal-
Mart are hoaxes powered by alkaline button cells.

On Fri, 12 May 2006 16:35:17 -0500, Richard J Kinch
wrote:

The latest fad has been these flashlights that you shake to charge.

The electrical energy available from that much shaking is insufficient to
charge a battery or run a flashlight. The ones I've seen such as at Wal-
Mart are hoaxes powered by alkaline button cells.

I dunno about the shaking ones, but the one I've got that
runs off a hand-crank works pretty well.

definetely batteries, my friend did a autopsey on one, standard button
hearing aid batteries. my friend put the batteries in a battery tester
they checked out nearly fully charged

the better emergency flashlight has a crank for charging.

Yes, they are batteries, (button type) in fact it says "lithium
battery CR2032 3V" on them.

At least I have a real magnet in mine, and likes to snag all the nails
and screws that end up in my pocket. And, as I said, the shaking does
light the LED to full brightness, but only for 10 or 15 seconds
without the batteries. Then the light remains dimly lit for another
half hour or less. There is a capacitor in there which charges from
the shaking.

I dont think lithium batteries are chargable (but I could be wrong).
Either way, without the batteries, almost constant shaking is needed
to maintain a bright light.

Mark


On Fri, 12 May 2006 11:23:32 GMT, "Joseph Meehan"
wrote:

wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

Thats why you never have to shake them when new.

I dismantled one, and found the batteries. I removed the batteries
and they work without the batteries as long as they are shook almost
constantly. They stay on for over an hour after being shook, but the
light is so dim it's useless, and a match is brighter.

Once again we as consumers, are being deceived by the advertisers.

On Fri, 12 May 2006 11:23:32 GMT, "Joseph Meehan"
wrote:

wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?


I've seen 3 shake flashlights, on one the capacitor is 1F (1 Farad),
the second it's hard to tell but looks like .5F, the third (a small
one) has .1F. There are no batteries in any of them.

That small one is essentially useless.

Thats why you never have to shake them when new.

I dismantled one, and found the batteries. I removed the batteries
and they work without the batteries as long as they are shook almost
constantly. They stay on for over an hour after being shook, but the
light is so dim it's useless, and a match is brighter.

Once again we as consumers, are being deceived by the advertisers.
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

On 12 May 2006 15:16:25 -0700, "
wrote:

definetely batteries, my friend did a autopsey on one, standard button
hearing aid batteries. my friend put the batteries in a battery tester
they checked out nearly fully charged

the better emergency flashlight has a crank for charging.

I have one of those. It's a radio too.

Now when I hear a radio show where they say "wind up your radios".
I'll be able to.
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

wrote:
The latest fad has been these flashlights that you shake to charge.
They contain a coil and magnet which charges a capacitor and lights
the LED. Well, they do work, but to keep the led bright you have to
shake them almost constantly.

I know many of you have played with them in the stores and say they
stay bright forever. WRONG......
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries. Thats why you never have to shake them when new.

I dismantled one, and found the batteries. I removed the batteries
and they work without the batteries as long as they are shook almost
constantly. They stay on for over an hour after being shook, but the
light is so dim it's useless, and a match is brighter.

Once again we as consumers, are being deceived by the advertisers.

Shake flashlights are a fad. "Hey, look! I'm the first on my block to
get one!" Know what I mean?

W : )

In article .com,
wrote:
A good buddy bought 2 at the rodgers ohio flea market. You did way
better than he did.

His flashlight worked off those 2 batteries but they went dead, and
shaking didnt work

It turned out the thing that shakes wasnt magnetic, which is needed for
charging and the little board was bad. My buddy is a retired
electronics engineer and found them interesting....

There have een other reports too, from tampa of the complete junk type.

I have seen two dollar stores in the western suburbs of Philadelphia
selling $2 shake flashlights. The packages were different.
In both cases the magnet was fake, the coil was shorted, and the circuit
board had no energy storage device other than non-rechargeable "coin"
batteries.

Meanwhile, I have heard of $2 shake flashlights that are not fake,
although I wonder how well they actually work.

Meanwhile, higher price shake flashlights do work, although many to most
are not that bright and don't maintain their brightness for long. Some
have both batteries and the shake-generator stuff.
One that was on display at a local hardware store so that people could
try it out did not work well, needing to be constantly shaken to provide
any decent light that was still less than that of a typical LED "keychain"
light.

It appears to me that the $30-$40 units at Target are pretty decent,
although they still have only one low-power LED and I expect them to
underperform a 2-AA size Mag Light.

Now for some review links in the "LED Museum" / "Punishment Zone"
site, http://ledmuseum.home.att.net:

http://ledmuseum.candlepower.us/second/shake2.htm - a "Diamond" unit

http://insulatorz.home.att.net/night1.htm - a "Nightstar" unit

http://ledmuseum.candlepower.us/fifth/shakefl2.htm - a dollar store fake

http://ledmuseum.candlepower.us/fifth/shakefl1.htm - a dollar store fake

- Don Klipstein )

In article ,
wrote:
Joseph Meehan wrote:
wrote:
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

I took one apart, and the flat disks were large hearing aid batteries.
Both wires from the shaker coil were soldered into the same hole of an
unstuffed PC board which might have charged the batteries charged if
it had been correctly assembled.

Did you check to see if the "magnet" attracted steel objects? I
disassembled two different $2 units, and got your findings as well as
finding that the "magnets" were not magnets. In addition, the batteries
that I found were CR2032, which I do not believe are rechargeable.

- Don Klipstein )

In article , Richard J
Kinch wrote:

The latest fad has been these flashlights that you shake to charge.

The electrical energy available from that much shaking is insufficient to
charge a battery or run a flashlight. The ones I've seen such as at Wal-
Mart are hoaxes powered by alkaline button cells.

If they made one with a decent magnet and coil and electronics one can
get good output. Let's consider say, one foot-pound per second, which I
consider fairly achievable from shaking. That's about 1.35 watts. A "1
watt" "Luxeon" LED actually is being given about 1.2 watts when "fully
powered". Check out the brightness of battery-powered flashlights that
have "1 watt" "Luxeon" LEDs. However, this "ideal" does not account for
runtime being longer than shaking time.

- Don Klipstein )

Craven Morehead wrote:
In the event of a disaster, one of these "shaker" flashlights could come in
handy so I've been exercising so I could keep one running for quite a while.
My wife calls me a pervert. What's with that?

And why would a blind guy need a flashlight?

(Don Klipstein) wrote in
:

In article ,
wrote:
Joseph Meehan wrote:
wrote:
These flashlights which are sold as batteryless, actually contain 2
flat disk batteries.

Are you sure there were not capacitors?

I took one apart, and the flat disks were large hearing aid batteries.
Both wires from the shaker coil were soldered into the same hole of an
unstuffed PC board which might have charged the batteries charged if
it had been correctly assembled.

Did you check to see if the "magnet" attracted steel objects? I
disassembled two different $2 units, and got your findings as well as
finding that the "magnets" were not magnets. In addition, the batteries
that I found were CR2032, which I do not believe are rechargeable.

- Don Klipstein )


amazing they can make a flashlight with TWO expensive CR2032 lithium cells
and sell it for TWO bucks and make a profit.

(mine was $3 at a 'doller' store;it appears to have two coin cells,which I
had wondered about,THX.)

--
Jim Yanik
jyanik
at
kua.net

(Don Klipstein) wrote in
:

In article , Richard J
Kinch wrote:

The latest fad has been these flashlights that you shake to charge.

The electrical energy available from that much shaking is insufficient
to charge a battery or run a flashlight. The ones I've seen such as
at Wal- Mart are hoaxes powered by alkaline button cells.

If they made one with a decent magnet and coil and electronics one
can
get good output. Let's consider say, one foot-pound per second, which
I consider fairly achievable from shaking. That's about 1.35 watts.
A "1 watt" "Luxeon" LED actually is being given about 1.2 watts when
"fully powered". Check out the brightness of battery-powered
flashlights that have "1 watt" "Luxeon" LEDs. However, this "ideal"
does not account for runtime being longer than shaking time.

- Don Klipstein )


If they used alkaline button cells,they would need THREE to power a white
led(needing ~3.5V). The CR2032 are lithium,output 3v per cell.

--
Jim Yanik
jyanik
at
kua.net

Jim Yanik wrote:

(Don Klipstein) wrote in
:
[...]

amazing they can make a flashlight with TWO expensive CR2032 lithium cells
and sell it for TWO bucks and make a profit.

(mine was $3 at a 'doller' store;it appears to have two coin cells,which I
had wondered about,THX.)


CR2032 batteries are NOT expensive, their replacement cost to a
non-manufacturer (ie consumer) can make you think that. Blame that on
mark-up and middlemen.
--
Grandpa

What is that dripping from my fingers?
Why it looks like time.

Don Klipstein writes:

Let's consider say, one foot-pound per second, which I
consider fairly achievable from shaking. That's about 1.35 watts.

This is way too optimistic.

Didn't you ever have one of those generators on your bicycle as a kid?
What a chore to crank, and you had the advantage of using your legs on
pedals.

In article , Richard J
Kinch wrote:
Don Klipstein writes:

Let's consider say, one foot-pound per second, which I
consider fairly achievable from shaking. That's about 1.35 watts.

This is way too optimistic.

Didn't you ever have one of those generators on your bicycle as a kid?
What a chore to crank, and you had the advantage of using your legs on
pedals.

I had those. They put out 3 watts, and were said to be 30% efficient,
with the biggest loss being in the area where the tire contacts the part
that the tire turns.
However, I did once use two - one for a headlight and one for a
taillight with a headlight bulb.

A younger adult biker in good shape can crank out 1/4 horsepower - about
185 watts.

Now there are bike generators that have a larger roller get turned by
the centerline of the tire and losses are much less there.

Now, there are flashlights with hand cranks, and they seem to do better
than many of those shake flashlights.

Meanwhile, I don't think it takes that much effort to lift a 5 pound
dumbbell 1 foot and put it back down once every five seconds. That's one
foot pound per second.

- Don Klipstein )

Mark Lloyd wrote:

On 12 May 2006 15:16:25 -0700, "
wrote:

definetely batteries, my friend did a autopsey on one, standard button
hearing aid batteries. my friend put the batteries in a battery tester
they checked out nearly fully charged

the better emergency flashlight has a crank for charging.

I got two of those at Costco -- Durapro, 2/$19.98 or thereabouts. I
wound mine up a couple of months ago and it's still bright; I just turn
it on for a few seconds at a time to look for something under the desk,
but still... OTOH, the one my Mom has runs down in a day -- every time
she uses it (mostly to look into her pantry) she has to wind it. It
achieves full brightness with a minute of cranking, though. And she can
use the exercise.

3 white LEDs, no radio. There's also a flasher with a couple of
flashing red LEDs, which seems kind of silly.

--
Cheers,
Bev
----------------------------------------------------------
"When I was in college, the only job I could get was
****ting on people's lawns. Sure, the owners complained,
but it was honest work and it kept me off welfare..."
-- M. Tabnik in mcfl (paraphrased)

Don Klipstein writes:

A younger adult biker in good shape can crank out 1/4 horsepower -
about
185 watts.

You mean for long periods, right? Simply climbing stairs is a lot more
power than that.

Meanwhile, I don't think it takes that much effort to lift a 5 pound
dumbbell 1 foot and put it back down once every five seconds. That's
one foot pound per second.

Still too optimistic.

At least half of shaking is wasted right off (having to muscle the
inertia to a stop). And you are shaking mostly dead weight of the
flashlight *and* your arm, not just the magnet or whatever is the
magnetic flux item (starting to sound like Doc in _Back to the Future_).

Most people would be quite uncomfortable just holding a forearm out
steady for more than a few minutes. They used to punish us in grade
school with that.

Shaking is a truly dismal generator principle. It just seems clever to
a casual, first impression.

The Real Bev writes:

There's also a flasher with a couple of
flashing red LEDs, which seems kind of silly.

It appeals to the rubes. "Oooo, pretty!"

Richard J Kinch wrote in
:

Don Klipstein writes:

A younger adult biker in good shape can crank out 1/4 horsepower -
about
185 watts.

You mean for long periods, right? Simply climbing stairs is a lot more
power than that.

Meanwhile, I don't think it takes that much effort to lift a 5 pound
dumbbell 1 foot and put it back down once every five seconds. That's
one foot pound per second.

Still too optimistic.

At least half of shaking is wasted right off (having to muscle the
inertia to a stop). And you are shaking mostly dead weight of the
flashlight *and* your arm, not just the magnet or whatever is the
magnetic flux item (starting to sound like Doc in _Back to the Future_).

It's not meant to be efficient,it's meant to be reliable;the light is
"supposed" to never need batteries and always be ready for use.

Most people would be quite uncomfortable just holding a forearm out
steady for more than a few minutes. They used to punish us in grade
school with that.

Shaking is a truly dismal generator principle. It just seems clever to
a casual, first impression.

Unless you use a bridge rectifier,the return stroke of the magnet induces
current in the opposite direction,and you would need a diode to block the
reverse current,the diode has a forward voltage drop (~0.4v if you use a
Schottky diode),and you lose the energy from the reverse current with a
single diode.


FYI,I took apart my $3 "shaker" LED light,and the "magnet" was just a piece
of unmagnetized plain steel rod,the coil wires were tucked under the lower
battery terminal,*not soldered to anything*,and the batteries were a CR2032
and a thinner CR2025,for a total of 6 volts.They evidently use the
(CR2025?)cell's internal resistance to limit LED current.

--
Jim Yanik
jyanik
at
kua.net

Jim Yanik wrote:

Unless you use a bridge rectifier...

And why not?

Nick

Jim Yanik writes:

It's not meant to be efficient,it's meant to be reliable;

But any number of more effective designs like a crank would be more
reliable. Shaking is just a gimmick to impress the rubes.

Even bartenders learn that arm-shaking is not a good mixing method; you
pivot the wrists.

Jim Yanik wrote in
:


FYI,I took apart my $3 "shaker" LED light,and the "magnet" was just a
piece of unmagnetized plain steel rod,the coil wires were tucked under
the lower battery terminal,*not soldered to anything*,and the
batteries were a CR2032 and a thinner CR2025,for a total of 6
volts.They evidently use the (CR2025?)cell's internal resistance to
limit LED current.


Addendum;interestingly,they used the same circuit board for the fake,and
the holes and copper traces are all there for 4 diodes(a bridge),a
resistor,and the capacitor.With the addition of those parts and a strong
magnet,the shaker-generator would be functional.I may shop around at
Skycraft Surplus and see what those parts would cost,just for grins.

--
Jim Yanik
jyanik
at
kua.net

On Mon, 15 May 2006 20:51:48 GMT, Mys Terry
wrote:

On Mon, 15 May 2006 14:43:03 -0500, Richard J Kinch wrote:

Jim Yanik writes:

It's not meant to be efficient,it's meant to be reliable;

But any number of more effective designs like a crank would be more
reliable. Shaking is just a gimmick to impress the rubes.


Not necessarily. A crank necessitates an opening in the case, which means you
can't make it very waterproof - at least not cheaply. By keeping all mechanisms
internal, you can effectively seal the case for even underwater use. For a
flashlight in a survival kit, the shake method would have some advantage in the
reliability department.


Mine works no matter which way you move the crank.
So if you want to use it underwater, you could
stick it in a 1-gallon ziplock, and move the crank
back and forth, instead of around and around.

Mys Terry writes:

For a
flashlight in a survival kit, the shake method would have some
advantage in the reliability department.

Yes, brilliant analysis. I am now reprovisioning my offshore survival kit
with Chinese flea market trinkets.

On 15 May 2006 13:33:39 GMT, Jim Yanik wrote:

Richard J Kinch wrote in
:

Don Klipstein writes:

A younger adult biker in good shape can crank out 1/4 horsepower -
about
185 watts.

You mean for long periods, right? Simply climbing stairs is a lot more
power than that.

Meanwhile, I don't think it takes that much effort to lift a 5 pound
dumbbell 1 foot and put it back down once every five seconds. That's
one foot pound per second.

Still too optimistic.

At least half of shaking is wasted right off (having to muscle the
inertia to a stop). And you are shaking mostly dead weight of the
flashlight *and* your arm, not just the magnet or whatever is the
magnetic flux item (starting to sound like Doc in _Back to the Future_).

It's not meant to be efficient,it's meant to be reliable;the light is
"supposed" to never need batteries and always be ready for use.

Most people would be quite uncomfortable just holding a forearm out
steady for more than a few minutes. They used to punish us in grade
school with that.

Shaking is a truly dismal generator principle. It just seems clever to
a casual, first impression.

Unless you use a bridge rectifier,the return stroke of the magnet induces
current in the opposite direction,and you would need a diode to block the
reverse current,the diode has a forward voltage drop (~0.4v if you use a
Schottky diode),and you lose the energy from the reverse current with a
single diode.


FYI,I took apart my $3 "shaker" LED light,and the "magnet" was just a piece
of unmagnetized plain steel rod,the coil wires were tucked under the lower
battery terminal,*not soldered to anything*,and the batteries were a CR2032
and a thinner CR2025,for a total of 6 volts.They evidently use the
(CR2025?)cell's internal resistance to limit LED current.

A LED is supposed to need SOME series resistance to work properly.
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin

Richard J Kinch wrote in
:

Jim Yanik writes:

It's not meant to be efficient,it's meant to be reliable;

But any number of more effective designs like a crank would be more
reliable.
(but more complicated and expensive)

I saw one of those at KMart,it had 3 5mm LEDs,they wanted $20 for it.
IMO,not a good deal.

Shaking is just a gimmick to impress the rubes.

Even bartenders learn that arm-shaking is not a good mixing method; you
pivot the wrists.




--
Jim Yanik
jyanik
at
kua.net

Mark Lloyd wrote in
:

On 15 May 2006 13:33:39 GMT, Jim Yanik wrote:

Richard J Kinch wrote in
1:

Don Klipstein writes:

A younger adult biker in good shape can crank out 1/4 horsepower
- about
185 watts.

You mean for long periods, right? Simply climbing stairs is a lot
more power than that.

Meanwhile, I don't think it takes that much effort to lift a 5
pound
dumbbell 1 foot and put it back down once every five seconds.
That's one foot pound per second.

Still too optimistic.

At least half of shaking is wasted right off (having to muscle the
inertia to a stop). And you are shaking mostly dead weight of the
flashlight *and* your arm, not just the magnet or whatever is the
magnetic flux item (starting to sound like Doc in _Back to the
Future_).

It's not meant to be efficient,it's meant to be reliable;the light is
"supposed" to never need batteries and always be ready for use.

Most people would be quite uncomfortable just holding a forearm out
steady for more than a few minutes. They used to punish us in grade
school with that.

Shaking is a truly dismal generator principle. It just seems clever
to a casual, first impression.

Unless you use a bridge rectifier,the return stroke of the magnet
induces current in the opposite direction,and you would need a diode
to block the reverse current,the diode has a forward voltage drop
(~0.4v if you use a Schottky diode),and you lose the energy from the
reverse current with a single diode.


FYI,I took apart my $3 "shaker" LED light,and the "magnet" was just a
piece of unmagnetized plain steel rod,the coil wires were tucked under
the lower battery terminal,*not soldered to anything*,and the
batteries were a CR2032 and a thinner CR2025,for a total of 6
volts.They evidently use the (CR2025?)cell's internal resistance to
limit LED current.

A LED is supposed to need SOME series resistance to work properly.

Many of the tiny keychain lights use the battery's -internal resistance- to
limit LED current.Some of those button cells cannot supply much current at
all.(high internal resistance)

--
Jim Yanik
jyanik
at
kua.net