Found Out Something Else Today

  • Thread starter Watson A.Name - "Watt Sun
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Watson A.Name - "Watt Sun

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I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
..375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
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My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
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Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
On Sun, 25 Jan 2004 16:54:46 -0800, Watson A.Name - "Watt Sun, Dark
Remover" <alondra101@hotmail.com> wrote:

I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.
Click to expand...
Beads are designed to be lossy. Seems a wee bit foolish to me to use
them for inductor cores.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
"Watson A.Name - Watt Sun, Dark Remover" wrote:
I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.
Click to expand...
It would definitely lower the "Q". You can wrap a thin strip of
paper around the core first, or spray paint the core first, to protect
the wire from the edges.


--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida
 
"Watson A.Name - Watt Sun, Dark Remover" wrote:
I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.
Click to expand...
The high permeability ferrites are all quite conductive (semi
conductive, actually), and this represents a resistive loss to any
inductor would on them. Think of the core as a single turn load with
a resistor. For one offs, I usually take the edges off the core with
silicon carbide sandpaper. If I am going to be pulling a lot of turns
through the hole, I may paint the ends of the core with a thin layer
of epoxy to protect the wire.

By the way, if you are making energy storage inductors, these ungapped
cores will saturate a only a few amp turns. I like to use the two
piece cores made to be put on power cords as RFI suppression. I
sandwich a layer of paper between the halves to make an energy storage
gap. It is also easy to wind wire around the individual halves than
it is to pull it through the hole.

--
John Popelish
 
On Sun, 25 Jan 2004 16:54:46 -0800, Watson A.Name - "Watt Sun, Dark
Remover" <alondra101@hotmail.com> Gave us:

I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.
Click to expand...
If you had, the inductance would have been LOWER than expected, not
higher. It is very likely that you made no such shorts. Mag wire
insulation is in the 1500 V range.

Wind four or six of them at ten turns each to see what your
tolerances are.

Typically, ferrites are in the 20% range. That is a considerable
number.
 
On Sun, 25 Jan 2004 18:09:49 -0700, Jim Thompson
<thegreatone@example.com> Gave us:

Beads are designed to be lossy. Seems a wee bit foolish to me to use
them for inductor cores.
Click to expand...
Good for snubbers, but not much else.
 
In article <54q81090tmov3mt0j9eupp3tcbdiv5qavh@4ax.com>,
thegreatone@example.com mentioned...
On Sun, 25 Jan 2004 16:54:46 -0800, Watson A.Name - "Watt Sun, Dark
Remover" <alondra101@hotmail.com> wrote:


I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.

Beads are designed to be lossy. Seems a wee bit foolish to me to use
them for inductor cores.
Click to expand...
Lossy at a few MHz and up. Much, much less lossy at a hundred kHz.

...Jim Thompson
Click to expand...

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In article <40146917.57806602@earthlink.net>,
mike.terrell@earthlink.net mentioned...
"Watson A.Name - Watt Sun, Dark Remover" wrote:

I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.

It would definitely lower the "Q". You can wrap a thin strip of
paper around the core first, or spray paint the core first, to protect
the wire from the edges.
Click to expand...
Yeah, I got some 600 grit wet-or-dry sandpaper that i may use on it.
I also started sanding down the other beads that I sawed in half with
a ceramic tile saw. I used a round 60 grit sanding disk for that, but
it's getting worn down on one side, where it's beginning to polish
instead of sand. That side may make a good way to take the edges off
the beads. Maybe I should save the dust and make an old fashioned
coherer.. Yeah, right.


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In article <40147535.8E07CD33@rica.net>, jpopelish@rica.net
mentioned...
"Watson A.Name - Watt Sun, Dark Remover" wrote:

I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.

The high permeability ferrites are all quite conductive (semi
conductive, actually), and this represents a resistive loss to any
inductor would on them. Think of the core as a single turn load with
a resistor. For one offs, I usually take the edges off the core with
silicon carbide sandpaper. If I am going to be pulling a lot of turns
through the hole, I may paint the ends of the core with a thin layer
of epoxy to protect the wire.

By the way, if you are making energy storage inductors, these ungapped
cores will saturate a only a few amp turns. I like to use the two
piece cores made to be put on power cords as RFI suppression. I
sandwich a layer of paper between the halves to make an energy storage
gap. It is also easy to wind wire around the individual halves than
it is to pull it through the hole.
Click to expand...
Sounds interesting, but the two halves are kind of largish for my
needs. That's why I picked these beads. I've been sawing the
suppressor beads from keyboard cables in half, and they're not too
big, about a half to 5/8 inches in diameter. But it's a hassle sawing
them in half. As for the winding, I'm only able to get ten turns on
them, and that only takes a minute or so to wind.

The guys on Candlepower Forum use a bead they buy from Digi-Key or
Mouser, and it has an even smaller center hole, so they can only wind
a few turns on it. It works okay.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
On Sun, 25 Jan 2004 21:02:29 -0500, John Popelish <jpopelish@rica.net>
wrote:


By the way, if you are making energy storage inductors, these ungapped
cores will saturate a only a few amp turns. I like to use the two
piece cores made to be put on power cords as RFI suppression. I
sandwich a layer of paper between the halves to make an energy storage
gap. It is also easy to wind wire around the individual halves than
it is to pull it through the hole.
Click to expand...
You shouldn't need to take measures to prevent saturation if you are using
them as RFI suppression common mode choke. The differential mode currents
will cancel and the core will not saturate. That is why you often find high
permeability toroids in CM choke applications.

--

Boris Mohar
 
"Watson A.Name - Watt Sun, Dark Remover" <alondra101@hotmail.com> wrote in
message news:MPG.1a7e193590e44922989b97@news.dslextreme.com...
In article <54q81090tmov3mt0j9eupp3tcbdiv5qavh@4ax.com>,
thegreatone@example.com mentioned...
On Sun, 25 Jan 2004 16:54:46 -0800, Watson A.Name - "Watt Sun, Dark
Remover" <alondra101@hotmail.com> wrote:


I bought a bag of 12 Amidon ferrite Beads, # FB-77-6301 so I could
make some more inductors for my V boost circuits. I wound about ten
turns of 24 gauge telephone wire on one, which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes with the beads, and it said
that some mixes are conductive. I thought that ferrite was mostly
glass, and was an insulator. So I measured one with my DMM and I
found that the resistance was down in the hundreds of ohms, much
_lower_ than I had expected. I had thought that I really didn't need
to wind them with pvc insulated wire, but now I'm thinking that it's
not such a bad idea after all. I have wound the toroids before and
seen the insulation scraped off the enameled wire by the sharp edges
of the totoid but I didn't think much about it. So it's possible that
it could short out with the low resistance material of this particular
toroid. That's something I never expected.

Beads are designed to be lossy. Seems a wee bit foolish to me to use
them for inductor cores.

Lossy at a few MHz and up. Much, much less lossy at a hundred kHz.

...Jim Thompson
Click to expand...

Perhaps use them as Memory Cores? ;)
 
X-No-Archive: yes
"Mark J." wrote in message
"Watson A.Name - Watt Sun, Dark Remover" wrote
in
thegreatone@example.com mentioned...
On Sun, 25 Jan 2004 16:54:46 -0800, Watson
A.Name - "Watt Sun, Dark
Remover" wrote:

I bought a bag of 12 Amidon ferrite Beads,
# FB-77-6301 so I could
make some more inductors for my V boost
circuits. I wound about ten
turns of 24 gauge telephone wire on one,
which is a toroidal sleeve
.375" OD, .194" ID, and .41" long. I
measured the inductance at 405
microhenrys, which is more than I expected.

I was reading the literature that comes
with the beads, and it said
that some mixes are conductive. I thought
that ferrite was mostly
glass, and was an insulator. So I measured
one with my DMM and I
found that the resistance was down in the
hundreds of ohms, much
_lower_ than I had expected. I had thought
that I really didn't need
to wind them with pvc insulated wire, but
now I'm thinking that it's
not such a bad idea after all. I have
wound the toroids before and
seen the insulation scraped off the
enameled wire by the sharp edges
of the totoid but I didn't think much about
it. So it's possible that
it could short out with the low resistance
material of this particular
toroid. That's something I never expected.

Beads are designed to be lossy. Seems a wee
bit foolish to me to use
them for inductor cores.

Lossy at a few MHz and up. Much, much less
lossy at a hundred kHz.

....Jim Thompson
Perhaps use them as Memory Cores? ;)
Click to expand...
Sometime ago I bought a "jar" of .08 dia memory
cores, I can get 4 to 6 turns of #28 to #30
enameled wire on them. They work great to
suppress RFI and since I got about 60,000 of them
for $3 I will likely never run out. I have strung
up to ten on a piece of #22 wire for a Power input
filter too. (Don't have the exact value of the
inductance or loss, but it worked!
 
That seems like a huge tradeoff, though -- you have a nice energy storage
gap, but your inductance goes way down and now you need a ton of wire. I
can certainly see doing this to get good linear inductance characteristics,
though.

Most of the switching supply designs I see don't have gaps in their
inductors, at least not explicitly (but you do have to design around
saturation). Is there something I'm missing?

"John Popelish" <jpopelish@rica.net> wrote in message
news:40147535.8E07CD33@rica.net...
"Watson A.Name - Watt Sun, Dark Remover" wrote:

-- snip --
By the way, if you are making energy storage inductors, these ungapped
cores will saturate a only a few amp turns. I like to use the two
piece cores made to be put on power cords as RFI suppression. I
sandwich a layer of paper between the halves to make an energy storage
gap. It is also easy to wind wire around the individual halves than
it is to pull it through the hole.

--
John Popelish
Click to expand...
 
Tim Wescott wrote:
That seems like a huge tradeoff, though -- you have a nice energy storage
gap, but your inductance goes way down and now you need a ton of wire. I
can certainly see doing this to get good linear inductance characteristics,
though.

Most of the switching supply designs I see don't have gaps in their
inductors, at least not explicitly (but you do have to design around
saturation). Is there something I'm missing?
Click to expand...
Is there something I'm missing, too? Like, there are millions of gaps
between the magnetic particles in the ferrite and the binder, which I
believe is ceramic, and is not magnetic. If so, why should there need
to be an additional air gap added?


"John Popelish" <jpopelish@rica.net> wrote in message
news:40147535.8E07CD33@rica.net...

"Watson A.Name - Watt Sun, Dark Remover" wrote:

-- snip --

By the way, if you are making energy storage inductors, these ungapped
cores will saturate a only a few amp turns. I like to use the two
piece cores made to be put on power cords as RFI suppression. I
sandwich a layer of paper between the halves to make an energy storage
gap. It is also easy to wind wire around the individual halves than
it is to pull it through the hole.

--
John Popelish
Click to expand...
 
"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:
Tim Wescott wrote:
That seems like a huge tradeoff, though -- you have a nice energy storage
gap, but your inductance goes way down and now you need a ton of wire. I
can certainly see doing this to get good linear inductance characteristics,
though.

Most of the switching supply designs I see don't have gaps in their
inductors, at least not explicitly (but you do have to design around
saturation). Is there something I'm missing?

Is there something I'm missing, too? Like, there are millions of gaps
between the magnetic particles in the ferrite and the binder, which I
believe is ceramic, and is not magnetic. If so, why should there need
to be an additional air gap added?
Click to expand...
The powdered metal cores have distributed gaps between high mu
particles, but the ferrite is (ideally) a single crystal, solid
material with no gaps. In order to get high permeability and low
hysterisis the material must reach high flux with low magnetization
(the definition of high mu). But ferrites do not have as high
saturation flux as iron (2,000 to 3,000 gauss versus 10,000 to 20,000
gauss). The energy stored in an inductance is 1/2 * L * I^2. So
using the core ungapped gives a high inductance for a low number of
turns but a low I^2. By adding a tiny gap, you lower the L by say a
factor of, say 25 but also raise the saturation magnetization by 25
(25 times as many amp turns to reach the same saturation flux). You
increase the turns count by 5 to get the inductance back (since
inductance goes as the square of the number of turns), but the
saturation flux still supports 5 times the current. But now the stored
energy has gone up by a factor of 25 (same L, 5 times the current,
squared). All that extra energy is stored in that tiny gap. Of
course, if you don't mind using a core volume with 25 times more
volume, you can store it there.

--
John Popelish
 
John Popelish wrote:
"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Tim Wescott wrote:

That seems like a huge tradeoff, though -- you have a nice energy storage
gap, but your inductance goes way down and now you need a ton of wire. I
can certainly see doing this to get good linear inductance characteristics,
though.

Most of the switching supply designs I see don't have gaps in their
inductors, at least not explicitly (but you do have to design around
saturation). Is there something I'm missing?

Is there something I'm missing, too? Like, there are millions of gaps
between the magnetic particles in the ferrite and the binder, which I
believe is ceramic, and is not magnetic. If so, why should there need
to be an additional air gap added?
Click to expand...

The powdered metal cores have distributed gaps between high mu
particles, but the ferrite is (ideally) a single crystal, solid
material with no gaps. In order to get high permeability and low
hysterisis the material must reach high flux with low magnetization
(the definition of high mu). But ferrites do not have as high
saturation flux as iron (2,000 to 3,000 gauss versus 10,000 to 20,000
gauss). The energy stored in an inductance is 1/2 * L * I^2. So
using the core ungapped gives a high inductance for a low number of
turns but a low I^2. By adding a tiny gap, you lower the L by say a
factor of, say 25 but also raise the saturation magnetization by 25
(25 times as many amp turns to reach the same saturation flux). You
increase the turns count by 5 to get the inductance back (since
inductance goes as the square of the number of turns), but the
saturation flux still supports 5 times the current. But now the stored
energy has gone up by a factor of 25 (same L, 5 times the current,
squared). All that extra energy is stored in that tiny gap. Of
course, if you don't mind using a core volume with 25 times more
volume, you can store it there.
Click to expand...
Well, the reason I wanted to use a higher mu core material in the first
place was to reduce the number of turns. That's so that the wire
resistance would not lower the peak current. When you have only a volt
and a half at a couple hundred mA to work with, you need all the
reduction in resistance you can get.

I think one possible solution is to work with the lower inductance by
raising the freq of oscillation. That allows the circuit to get by with
less turns and less reasistance. I don't know how they do it, but the
commercial V boost circuits use inductors smaller than the size of a
pencil eraser, maybe about the size of a 5 mm LED but not as tall. And
they're also surface mount, making them really squat, like the size of a
3 mm screw head. And apparently to get around the internal resistance,
the inductance is lower, maybe 10 uH or less. The freq may be as high
as .5 to 2 MHz in some of the Zetex, Maxim and LT chips.

For an example of a converter using a (not so) small ferrite bead with
no air gap and just a few turns, see URL (thanks, Stepan)
http://www.e-f-w.com/community/modules.php?name=News&file=article&sid=32
 
"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Well, the reason I wanted to use a higher mu core material in the first
place was to reduce the number of turns.
Click to expand...
And you can do that by just using more core volume than the absolute
minimum. But it is hard to get low losses this way, because of the
higher volts per turn applied to the core resistance. But for very
low power operations, having a core several times the smallest
possible may still be plenty small.

That's so that the wire
resistance would not lower the peak current. When you have only a volt
and a half at a couple hundred mA to work with, you need all the
reduction in resistance you can get.
(snip)
Click to expand...

--
John Popelish
 
In article <4016EEA4.336A536A@rica.net>, jpopelish@rica.net
mentioned...
"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Well, the reason I wanted to use a higher mu core material in the first
place was to reduce the number of turns.

And you can do that by just using more core volume than the absolute
minimum. But it is hard to get low losses this way, because of the
higher volts per turn applied to the core resistance. But for very
low power operations, having a core several times the smallest
possible may still be plenty small.
Click to expand...
You say "absolute minimum" and "smallest possible" but I have no way
of knowing what these are. I have used some 180 uH chokes that are
smallish, maybe 6 mm diameter by 7 mm long, and they worked, but their
resistance was too high, maybe 1.5 ohms. So I got some 100 uH chokes
from Mouser, # 580-22R104, which are about 8 mm diameter by 10 mm
long. They have a resistance less than a half ohm, and can handle a
lot of current, so I have no problem driving three white LEDs to super
brightness and sucking 200 or more mA from a single AA cell.

The guys on Candlepower Forum use a smallish core, and enough current
to drive a 1 Watt Luxeon Star LED to full brightness. One of their
small converters is called the "Ill Pill"
http://flashlightreviews.home.att.net/mods/lambda_ill_pill.htm

That's so that the wire
resistance would not lower the peak current. When you have only a volt
and a half at a couple hundred mA to work with, you need all the
reduction in resistance you can get.
(snip)
Click to expand...

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In news:MPG.1a81027aab4c6445989b9f@news.dslextreme.com (Watson A.Name -
Watt Sun, Dark Remover):
In article <4016EEA4.336A536A@rica.net>, jpopelish@rica.net
mentioned...
"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Well, the reason I wanted to use a higher mu core material in the
first place was to reduce the number of turns.

And you can do that by just using more core volume than the absolute
minimum. But it is hard to get low losses this way, because of the
higher volts per turn applied to the core resistance. But for very
low power operations, having a core several times the smallest
possible may still be plenty small.

You say "absolute minimum" and "smallest possible" but I have no way
of knowing what these are. I have used some 180 uH chokes that are
smallish, maybe 6 mm diameter by 7 mm long, and they worked, but their
resistance was too high, maybe 1.5 ohms. So I got some 100 uH chokes
from Mouser, # 580-22R104, which are about 8 mm diameter by 10 mm
long. They have a resistance less than a half ohm, and can handle a
lot of current, so I have no problem driving three white LEDs to super
brightness and sucking 200 or more mA from a single AA cell.

The guys on Candlepower Forum use a smallish core, and enough current
to drive a 1 Watt Luxeon Star LED to full brightness. One of their
small converters is called the "Ill Pill"
http://flashlightreviews.home.att.net/mods/lambda_ill_pill.htm
Click to expand...

How long do those AA batteries last at 200mA/cell???
 
"Mark J." <127.0.0.1> wrote in news:SY2dnUmJ3c0tBYXd4p2dnA@buckeye-
express.com:

In news:MPG.1a81027aab4c6445989b9f@news.dslextreme.com (Watson A.Name -
Watt Sun, Dark Remover):
In article <4016EEA4.336A536A@rica.net>, jpopelish@rica.net
mentioned...
"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Well, the reason I wanted to use a higher mu core material in the
first place was to reduce the number of turns.

And you can do that by just using more core volume than the absolute
minimum. But it is hard to get low losses this way, because of the
higher volts per turn applied to the core resistance. But for very
low power operations, having a core several times the smallest
possible may still be plenty small.

You say "absolute minimum" and "smallest possible" but I have no way
of knowing what these are. I have used some 180 uH chokes that are
smallish, maybe 6 mm diameter by 7 mm long, and they worked, but their
resistance was too high, maybe 1.5 ohms. So I got some 100 uH chokes
from Mouser, # 580-22R104, which are about 8 mm diameter by 10 mm
long. They have a resistance less than a half ohm, and can handle a
lot of current, so I have no problem driving three white LEDs to super
brightness and sucking 200 or more mA from a single AA cell.

The guys on Candlepower Forum use a smallish core, and enough current
to drive a 1 Watt Luxeon Star LED to full brightness. One of their
small converters is called the "Ill Pill"
http://flashlightreviews.home.att.net/mods/lambda_ill_pill.htm



How long do those AA batteries last at 200mA/cell???
Click to expand...
I know it's OT, but since you brought up the thought about current per
cell...

I was given one of those little tiny digital cameras, about 2" square and
about 3/4" thick. I forget the name. Anyway, the single AAA battery
never would last long enough to even fill the memory with images, so I
checked it out. It was drawing a whopping 850ma from a single AAA
battery! No wonder it was given away. I will concede that there MAY
have been something wrong with it, however it took quite good pictures
and worked well, with the exception of battery life. It was supposedly
the smallest digital camera in the world, at the time of its release and
I don't mean a video camera, rather a digital, single image camera that
you could download images from, to a computer thru USB. No flash. res
was 1024x768(probably interpolated)

buck
 
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