Ferrite Bead

Al · Dec 11, 2009

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2606824

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Cheers

-Al

Rich Webb · Dec 11, 2009

On Thu, 10 Dec 2009 18:10:37 -0800 (PST), Al <bigal.nz@gmail.com> wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2606824

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Try the gizmo available over at
http://www.dl5swb.de/html/mini_ring_core_calculator.htm

--
Rich Webb Norfolk, VA

Al · Dec 11, 2009

On Dec 11, 3:21 pm, Rich Webb <bbew...@mapson.nozirev.ten> wrote:

On Thu, 10 Dec 2009 18:10:37 -0800 (PST), Al <bigal...@gmail.com> wrote:
Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Try the gizmo available over athttp://www.dl5swb.de/html/mini_ring_core_calculator.htm

--
Rich Webb Norfolk, VA

Looks like a good tool, but I know nothing about my ferrite bead
except that its:

1. Works on a circuit 19v up to 4.7a
2. 2.5 turns
3. 10mm length
4. 6mm dia

Thats not enough to work out the resistance is it?

Dec 11, 2009

On Dec 10, 6:10 pm, Al <bigal...@gmail.com> wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Cheers

-Al

You'll need to know what ferite material is used. This may give you
some ideas.

http://www.fair-rite.com/newfair/materials.htm

G˛

Al · Dec 11, 2009

On Dec 11, 6:37 pm, stratu...@yahoo.com wrote:

On Dec 10, 6:10 pm, Al <bigal...@gmail.com> wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Cheers

-Al

You'll need to know what ferite material is used. This may give you
some ideas.

http://www.fair-rite.com/newfair/materials.htm

G˛

Thanks for that link - reading it now. Since I first made the post I
have noticed two things:

1. Almost all the ferrite beads with 2.5 turns that I have seen on
component websites seem to have spec sheets that show freq response
from 1Mhz through to 1000Mhz with corresponding resistance vales
typically in the range 100-700Ohms.

I assume therefore that if this ferrite choke is anything like the
ones I have found, it is not so much for suppressing mains hum but
more likely high freq rf interference and the like? (whats more there
is another choke on the dc side of the ac adapter for the laptop which
looks more geared to mains hum)

2. If you know the:
Length
Diameter
Turns
Wire size
of a given bead, and the above can be measured, can you calculate the
Impedance @ a Frequency (F)?

I realise not knowing the exact ferrite material may require some
generalizations in any equation related to the above.

Its prob not ideal, but I am beginning to think I will get away with
any wide band ferrite bead in a similar packaging may do the trick?

-Al

Bob Larter · Dec 12, 2009

On 11/12/2009 1:10 PM, Al wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2606824

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Why do you care? It sounds like a simple ferrite line filter, which are
very non-critical in value.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

Bob Larter · Dec 12, 2009

On 11/12/2009 1:53 PM, Al wrote:

On Dec 11, 3:21 pm, Rich Webb<bbew...@mapson.nozirev.ten> wrote:
On Thu, 10 Dec 2009 18:10:37 -0800 (PST), Al<bigal...@gmail.com> wrote:
Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Try the gizmo available over athttp://www.dl5swb.de/html/mini_ring_core_calculator.htm

--
Rich Webb Norfolk, VA

Looks like a good tool, but I know nothing about my ferrite bead
except that its:

1. Works on a circuit 19v up to 4.7a
2. 2.5 turns
3. 10mm length
4. 6mm dia

Thats not enough to work out the resistance is it?

You mean inductance, surely? If you want to know the resistance, simply
measure it with your multimeter.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

Bob Larter · Dec 12, 2009

On 11/12/2009 7:49 PM, Al wrote:

On Dec 11, 6:37 pm, stratu...@yahoo.com wrote:
On Dec 10, 6:10 pm, Al<bigal...@gmail.com> wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Cheers

-Al

You'll need to know what ferite material is used. This may give you
some ideas.

http://www.fair-rite.com/newfair/materials.htm

G˛

Thanks for that link - reading it now. Since I first made the post I
have noticed two things:

1. Almost all the ferrite beads with 2.5 turns that I have seen on
component websites seem to have spec sheets that show freq response
from 1Mhz through to 1000Mhz with corresponding resistance vales
typically in the range 100-700Ohms.

I assume therefore that if this ferrite choke is anything like the
ones I have found, it is not so much for suppressing mains hum but
more likely high freq rf interference and the like? (whats more there
is another choke on the dc side of the ac adapter for the laptop which
looks more geared to mains hum)

2. If you know the:
Length
Diameter
Turns
Wire size
of a given bead, and the above can be measured, can you calculate the
Impedance @ a Frequency (F)?

I realise not knowing the exact ferrite material may require some
generalizations in any equation related to the above.

Its prob not ideal, but I am beginning to think I will get away with
any wide band ferrite bead in a similar packaging may do the trick?

Ah. If you just want to replace a broken one, any similar-looking one
should do the trick.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

isw · Dec 12, 2009

In article <hfva1u$k0o$2@blackhelicopter.databasix.com>,
Bob Larter <bobbylarter@gmail.com> wrote:

On 11/12/2009 1:10 PM, Al wrote:
Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?method=ge
tProduct&R=2606824

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Why do you care? It sounds like a simple ferrite line filter, which are
very non-critical in value.

ISTR that those things are spec'ed in terms of "equivalent resistance at
certain frequencies" (which probably makes them easy to specify).
They're just a few inches of (probably) #20 wire.

Isaac

isw · Dec 12, 2009

In article
<2ac45e7a-8142-47e5-baf8-1d1974557aaa@d9g2000prh.googlegroups.com>,
Al <bigal.nz@gmail.com> wrote:

On Dec 11, 6:37 pm, stratu...@yahoo.com wrote:
On Dec 10, 6:10 pm, Al <bigal...@gmail.com> wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Cheers

-Al

You'll need to know what ferite material is used. This may give you
some ideas.

http://www.fair-rite.com/newfair/materials.htm

G˛

Thanks for that link - reading it now. Since I first made the post I
have noticed two things:

1. Almost all the ferrite beads with 2.5 turns that I have seen on
component websites seem to have spec sheets that show freq response
from 1Mhz through to 1000Mhz with corresponding resistance vales
typically in the range 100-700Ohms.

I assume therefore that if this ferrite choke is anything like the
ones I have found, it is not so much for suppressing mains hum but
more likely high freq rf interference and the like? (whats more there
is another choke on the dc side of the ac adapter for the laptop which
looks more geared to mains hum)

You do realize that its purpose is to keep nasty stuff *in* the box, not
the other way around?

Any choke that was effective at mains frequencies would be a *whole lot*
larger.

Isaac

isw · Dec 12, 2009

In article <hfva69$k0o$4@blackhelicopter.databasix.com>,
Bob Larter <bobbylarter@gmail.com> wrote:

On 11/12/2009 7:49 PM, Al wrote:
On Dec 11, 6:37 pm, stratu...@yahoo.com wrote:
On Dec 10, 6:10 pm, Al<bigal...@gmail.com> wrote:

Hi all,

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?me...

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

I assume that I can workout which bead my unknown one is out of the
laptop by putting a 25Mhz sine wave signal through the bead and using
a formula to work out the resistance?

If so, what is the formula?

Cheers

-Al

You'll need to know what ferite material is used. This may give you
some ideas.

http://www.fair-rite.com/newfair/materials.htm

G˛

Thanks for that link - reading it now. Since I first made the post I
have noticed two things:

1. Almost all the ferrite beads with 2.5 turns that I have seen on
component websites seem to have spec sheets that show freq response
from 1Mhz through to 1000Mhz with corresponding resistance vales
typically in the range 100-700Ohms.

I assume therefore that if this ferrite choke is anything like the
ones I have found, it is not so much for suppressing mains hum but
more likely high freq rf interference and the like? (whats more there
is another choke on the dc side of the ac adapter for the laptop which
looks more geared to mains hum)

2. If you know the:
Length
Diameter
Turns
Wire size
of a given bead, and the above can be measured, can you calculate the
Impedance @ a Frequency (F)?

I realise not knowing the exact ferrite material may require some
generalizations in any equation related to the above.

Its prob not ideal, but I am beginning to think I will get away with
any wide band ferrite bead in a similar packaging may do the trick?

Ah. If you just want to replace a broken one, any similar-looking one
should do the trick.

Actually, if it's broken, you an probably just forget about it, unless
you see evidence that the box is causing interference to other gear
nearby.

Isaac

Jeff Liebermann · Dec 12, 2009

On Thu, 10 Dec 2009 18:10:37 -0800 (PST), Al <bigal.nz@gmail.com>
wrote:

I have here a Ferrite bead. Its from inside a laptop and is the first
component before the DC cable even hits the motherboard.

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

http://newzealand.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2606824

It has no part numbers on it whatsoever.

Looking at the RS-Online website there seem to be about 5/6 "possible"
ferrite beads it could be. All these suspect beads have Resistance @
25Mhz and 100Mhz listed as attributes.

<http://www.we-online.de/katalog/de/we/katalog/index.php?language=en&key=EMC_Ferrites%2FFerrites_for_PCB_assembly%2FKatalog%2FWE-UKW>

Shove 25Mhz or 100MHz into the existing ferrite bead and measure it's
impedance. Just a signal generator, the bead, and a 1Kohm load.
Measure the voltage out of the generator, and the voltage across the
load, using an RF volts guesser, or an oscilloscope. The rest is
calculating the divider ratio between the bead impedance and the 1Kohm
load.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Wild_Bill · Dec 13, 2009

Measuring the resistance such a short piece of wire isn't as trivial as
using a common multimeter.

One way to accurately measure small resistance values is with a milliohm
meter, digital models typically have 3 digits to the right of the decimal.
The connections to a milliohm meter need to be secure, not just merely
touching a couple of probe tips to the ends of a wire.

--
Cheers,
WB
..............

"Bob Larter" <bobbylarter@gmail.com> wrote in message
news:hfva3n$k0o$3@blackhelicopter.databasix.com...

On 11/12/2009 1:53 PM, Al wrote:
On Dec 11, 3:21 pm, Rich Webb<bbew...@mapson.nozirev.ten> wrote:
On Thu, 10 Dec 2009 18:10:37 -0800 (PST), Al<bigal...@gmail.com> wrote:

Its got about 2.5 turns, ferrite outside dia approx 5mm and length
approx 10mm and looks very similar to :

Thats not enough to work out the resistance is it?

You mean inductance, surely? If you want to know the resistance, simply
measure it with your multimeter.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

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