On Thu, 10 Jun 2004 17:04:02 GMT, Jan Panteltje
wrote:


That reminds me of this movie 'flying high' I think it was,
where the pilot is in conversation with the air traffic controller named
Roger.
Roger Roger!

---
"AIRPLANE!", I believe.

--
John Fields

Terry Given wrote:
[snip]

I design lots of magnetic devices. One of the first things I do with a
prototype transformer is dismantle it - I look at insulation, wire type,
winding pitch etc, AND I specifically count the number of turns (my
Leatherman has gutted hundreds of transformers I also measure coupling,
saturation, DC resistance, capacitance etc

If I had 2 of those bobbin core coils, I would just unwind the damn thing
and count the number of turns.

Ultimately, pay attention to John Larkin. A mate once had a 3-phase inductor
made (for a 600kW Butterworth filter that was hopeless - fringing flux
and leakage totally ruined the current distribution, making it glow red hot.
OTOH it made a great heater

Is this a movie of that "heater"??? :-))) (Warning: 5 Megabyte .MPG)
http://205.243.100.155/frames/mpg/XfrmBlast1.mpg

Cheers
Terry

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

Terry Given wrote:
[snip]

I design lots of magnetic devices. One of the first things I do with a
prototype transformer is dismantle it - I look at insulation, wire type,
winding pitch etc, AND I specifically count the number of turns (my
Leatherman has gutted hundreds of transformers I also measure
coupling,
saturation, DC resistance, capacitance etc

If I had 2 of those bobbin core coils, I would just unwind the damn thing
and count the number of turns.


Ultimately, pay attention to John Larkin. A mate once had a 3-phase
inductor
made (for a 600kW Butterworth filter that was hopeless - fringing flux
and leakage totally ruined the current distribution, making it glow
red hot.
OTOH it made a great heater


Is this a movie of that "heater"??? :-))) (Warning: 5 Megabyte .MPG)
http://205.243.100.155/frames/mpg/XfrmBlast1.mpg

Ooh, COOL! He's got another even bigger one!! Warning: 1.5 MB .MPG
http://205.243.100.155/frames/mpg/500kV_Switch.mpg
See www.teslamania.com for the text associated with this video clip.

Cheers
Terry

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On a sunny day (Thu, 10 Jun 2004 16:56:03 -0700) it happened "Watson A.Name
\"Watt Sun - the Dark Remover\"" wrote in
:

Ooh, COOL! He's got another even bigger one!! Warning: 1.5 MB .MPG
http://205.243.100.155/frames/mpg/500kV_Switch.mpg
Am I imagining this or do I see a woman in that white plasma?
hehehe

See www.teslamania.com for the text associated with this video clip.

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"Watson A.Name "Watt Sun - the Dark Remover"" wrote
in message ...
Terry Given wrote:
[snip]

Is this a movie of that "heater"??? :-))) (Warning: 5 Megabyte .MPG)
http://205.243.100.155/frames/mpg/XfrmBlast1.mpg

Well, they're Green. No PCBs there!

Cheers!
Rich

"John Fields" wrote in message
news
On Thu, 10 Jun 2004 17:04:02 GMT, Jan Panteltje
wrote:


That reminds me of this movie 'flying high' I think it was,
where the pilot is in conversation with the air traffic controller named
Roger.
Roger Roger!

---
"AIRPLANE!", I believe.

--
John Fields

quite funny. it reminded me of a book I once read - airscream I think it was
called. about 1/2 way thru the book the inevitable plane crash occurred, and
(AFAICR) EVERY character was killed - those who werent in the plane got hit
by wreckage, which was pretty funny. When I realised the auther was
introducing a new cast, I gave up

Cheers
Terry

On Fri, 11 Jun 2004 15:42:21 +1200, "Terry Given"
wrote:

"John Fields" wrote in message
news
On Thu, 10 Jun 2004 17:04:02 GMT, Jan Panteltje
wrote:


That reminds me of this movie 'flying high' I think it was,
where the pilot is in conversation with the air traffic controller named
Roger.
Roger Roger!

---
"AIRPLANE!", I believe.

--
John Fields

quite funny. it reminded me of a book I once read - airscream I think it was
called. about 1/2 way thru the book the inevitable plane crash occurred, and
(AFAICR) EVERY character was killed - those who werent in the plane got hit
by wreckage, which was pretty funny. When I realised the auther was
introducing a new cast, I gave up

Cheers
Terry


I've seen a number of movies - in particular a number of the BBC
mysteries - where I wished all the characters had been offed. In
Jurassic Park, I was rooting for the dinosaurs.

John

John Larkin wrote:

On Fri, 11 Jun 2004 15:42:21 +1200, "Terry Given"
wrote:



"John Fields" wrote in message
news

On Thu, 10 Jun 2004 17:04:02 GMT, Jan Panteltje
wrote:




That reminds me of this movie 'flying high' I think it was,
where the pilot is in conversation with the air traffic controller named
Roger.
Roger Roger!


---
"AIRPLANE!", I believe.

--
John Fields


quite funny. it reminded me of a book I once read - airscream I think it was
called. about 1/2 way thru the book the inevitable plane crash occurred, and
(AFAICR) EVERY character was killed - those who werent in the plane got hit
by wreckage, which was pretty funny. When I realised the auther was
introducing a new cast, I gave up

Cheers
Terry




I've seen a number of movies - in particular a number of the BBC
mysteries - where I wished all the characters had been offed. In
Jurassic Park, I was rooting for the dinosaurs.

John



Not hard enough.

"Bill Jeffrey" wrote in message
...
Watson A.Name - "Watt Sun, the Dark Remover" wrote:
"Bill Jeffrey" wrote in message
...

What am I missing here? If you know the inductance of the original
coil, there are formulas that will tell you the number of turns.
Wind

a

coil according to the formula, measure the inductance, and tweak the
number of turns to get as close as you need to be.

Bill
====================


Okay, I have two identical adjustable core coils, one with the slug
all
the way in and the other all the way out. The Out one measures 100
uH
and the In one measures 180 uh. I put both into a box, each with
terminals to the outside, so that the physical coil can't be seen.
Then
I give them to you along with the inductance of each, and you tell
me
that, by your formulas, the Out one has a different number of turns
than
the In one????

No, I'm saying that you take the slug all the way out, and the bobbin
off the pot core/cup core, so you have an air core coil. Measure the
inductance and plug it into the formula. (You did say that it's wound
on a bobbin, which usually implies that you can get the bobbin off the
ferrite.)

There are many formulas for calculating inductance. All of them admit
to being approximations - but that's all you need. For example:

"For a coil of rectangular cross-section, of thickness t inches,
length
l inches and mean diameter (average of inside and outside) d inches,
Hazletine's formula is L = 0.8d^2N^2 /(12d + 36l + 40t) uH"

Now if your entire coil, including the ferrite, is potted in epoxy, it
is a different situation. But I don't see that in any of your posts.

Thanks for the info.

I guess I didn't say it outright, but I meant that the core was a bobbin
made of ferrite, so it can't be removed. And I did say that it could be
a toroid which is the same situation. Also, I didn't mention it but I
thought this could also be applied to a winding on a solenoid or motor.
In any case, removing the core from a bobbin in my experience is usually
destructive, or else the core won't go back in without having a major
problem, such as not fitting properly and hence the inductance won't be
the same as the original coil. This is because most ferrite bobbins
I've seen are glued to the core with epoxy or similar, and are a real
bitch to remove. So to me, that's not practical. Like someone
mentioned, it would be just as practical to cut the coil and count the
turns.



Bill