Shaker LED flashlight

[amdx]

Just for fun and as a reinforcement of the electricity
books my son has been reading. I bought a shaker flashlight. (magnetic flux
cutting across wire moving electrons , the electrons then stored on plates
of a capacitor) The flashlight has a magnet that slides back and forth
through a coil. The flashlight cost $1.00.
After I opened the package I noted a small screw rattling
inside the light, so I took it apart and I found two cr2032
lithium batteries in series powering the LED. The coil is connected to a
fullwave bridge and the unit has a .22f
capacitor. There is a 10 ohm resistor in series with the LED.
If I remove the batteries and short across the holder the
LED will not light, no matter how much I shake it.
I just found the batteries in there to be a disappointment.
Mike

 

[DJ Delorie]

If I remove the batteries and short across the holder the
LED will not light, no matter how much I shake it.

Have you tried removing the batteries and NOT shorting the holder?
They may be using the batteries as storage devices.

 

[Phil Hobbs]

Have you tried removing the batteries and NOT shorting the holder?
They may be using the batteries as storage devices.

Nope, they're nearly always lithium coin cells, which are primary cells
(i.e. not rechargeable). It's a gimmick to attract the ignorant. The
coil doesn't even slow down the weight as it goes by, so how is it going
to extract any energy from it?

Try dropping a rare-earth magnet down a copper tube, if you want to see
what a shake-type generator ought to look like.

Cheers,

Phil Hobbs

 

[DJ Delorie]

Try dropping a rare-earth magnet down a copper tube, if you want to
see what a shake-type generator ought to look like.

I have a shakey light. It has a clear case, you can see all the
circuitry. No batteries.

But the OPs light may still work without the batteries if the
remainder of the circuit is properly designed.

 

[amdx]

Have you tried removing the batteries and NOT shorting the holder?
They may be using the batteries as storage devices.

Since my post I drew out the schematic and yes, by shorting the battery
holder I was shorting the storage capacitor. The LED does light, but very
dimly. Also I
noted the capacitor was not soldered to the board, it
just had the leads bent.
Interesting also is that the 5.5v capacitor has 6v of batteries across it.
Mike

 

[James Arthur]

I have a shakey light. It has a clear case, you can see all the
circuitry. No batteries.

But the OPs light may still work without the batteries if the
remainder of the circuit is properly designed.

amdx has a rip-off--those use coin cells. The original, authentic
shake light used coil+magnet.

Best,
James Arthur

 

[Phil Hobbs]

I have a shakey light. It has a clear case, you can see all the
circuitry. No batteries.

But the OPs light may still work without the batteries if the
remainder of the circuit is properly designed.

I don't mean it can't be done. But all the ones I've seen had coin cells.

Cheers,

Phil Hobbs

 

[[email protected]]

Just for fun and as a reinforcement of the electricity
books my son has been reading. I bought a shaker flashlight. (magnetic flux
cutting across wire moving electrons , the electrons then stored on plates
of a capacitor) The flashlight has a magnet that slides back and forth
through a coil. The flashlight cost $1.00.
After I opened the package I noted a small screw rattling
inside the light, so I took it apart and I found two cr2032
lithium batteries in series powering the LED. The coil is connected to a
fullwave bridge and the unit has a .22f
capacitor. There is a 10 ohm resistor in series with the LED.
If I remove the batteries and short across the holder the
LED will not light, no matter how much I shake it.
I just found the batteries in there to be a disappointment.
Mike

Well, the good news is, you now know of a cheap source of CR2032
batteries (which can be expensive elsewhere)...

Michael

 

[linnix]

Well, the good news is, you now know of a cheap source of CR2032
batteries (which can be expensive elsewhere)...

Michael

Actually, there are cheaper sources. I got some of them for a penny
each, after throwing away the ASIC and 100 SMD LEDs. I need a few
thousands of them, but it wouldn't justify the gas cost. CR2032s are
approximately 25 cents each in volume.

 

[linnix]

Actually, there are cheaper sources. I got some of them for a penny
each, after throwing away the ASIC and 100 SMD LEDs. I need a few
thousands of them, but it wouldn't justify the gas cost. CR2032s are
approximately 25 cents each in volume.

Correction, digikey has them for 14 cents each in QTY 4000.

 

[[email protected]]

Actually, there are cheaper sources. I got some of them for a penny
each, after throwing away the ASIC and 100 SMD LEDs. I need a few
thousands of them, but it wouldn't justify the gas cost. CR2032s are
approximately 25 cents each in volume.

Where'd you get the ASIC and LEDs?

I've got to stop shopping at Wal-Mart...

M

 

[linnix]

Where'd you get the ASIC and LEDs?

I've got to stop shopping at Wal-Mart...

M

Try the yellow one next to it.

 

[Jim Yanik]

Just for fun and as a reinforcement of the electricity
books my son has been reading. I bought a shaker flashlight. (magnetic
flux cutting across wire moving electrons , the electrons then
stored on plates of a capacitor) The flashlight has a magnet that
slides back and forth through a coil. The flashlight cost $1.00.
After I opened the package I noted a small screw rattling
inside the light, so I took it apart and I found two cr2032
lithium batteries in series powering the LED. The coil is connected to
a fullwave bridge and the unit has a .22f
capacitor. There is a 10 ohm resistor in series with the LED.
If I remove the batteries and short across the holder the
LED will not light, no matter how much I shake it.
I just found the batteries in there to be a disappointment.
Mike

mine had a CR2032 and a CR2025,NO CAP,coil not connected,the "magnet" was
an unmagnetized soft iron slug.

 

[Jim Yanik]

Nope, they're nearly always lithium coin cells, which are primary cells
(i.e. not rechargeable). It's a gimmick to attract the ignorant. The
coil doesn't even slow down the weight as it goes by, so how is it going
to extract any energy from it?

Try dropping a rare-earth magnet down a copper tube, if you want to see
what a shake-type generator ought to look like.

Cheers,

Phil Hobbs

who says the "magnet" really IS a magnet?
Mine wasn't. just a soft iron slug.

 

[Phil Hobbs]

who says the "magnet" really IS a magnet?
Mine wasn't. just a soft iron slug.

On the fakes, I'm sure it is. That's why it doesn't interact with the
coil. No dB/dt, no induced voltage, no opposing magnetization, no drag
on the weight--rattle rattle.

Terminal velocity for a 5/16 inch NdFeB magnet dropped down a 1/2 inch
copper pipe is about 1 foot per second. You can easily see the
difference between copper, aluminum, and brass tubes due to their
conductivity. It's pretty interesting to watch.

Cheers,

Phil Hobbs

 

[ehsjr]

I don't mean it can't be done. But all the ones I've seen had coin cells.

Cheers,

Phil Hobbs

Yup lots of fakes, or so I've heard.
Mine has no batteries, and the illumination
is proportional to the # of shakes, up to a point
where additional shakes make no change. And it has
a magnet, of course. Damn thing can almost support
the flashlight's weight when held against the 'fridge.

Ed

 

[amdx]

Well, the good news is, you now know of a cheap source of CR2032
batteries (which can be expensive elsewhere)...

Michael

 

[amdx]

Well, the good news is, you now know of a cheap source of CR2032
batteries (which can be expensive elsewhere)...

Michael

I was going to post, at least I got two cr2032 batteries inexpensively,
but then I decided they are probably worth what I paid for them.
Mike

 

[amdx]

Correction, digikey has them for 14 cents each in QTY 4000.

And only $4.99 at Radio Shack!
Mike