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Coil formula

  • Thread starter Dirk Bruere at Neopax
  • Start date
J

John Larkin

Jan 1, 1970
0
In case you missed it we had a New One.

It's like it's dead special...

Like you think a Millenium has something to do with a Million things.

It was probably something invented by Greeks and adopted by the Romans so it
got divided by a thousand, you know, like towards the end.

Like in modern times.... third fourth and fifth reich. Cherry blossoms of
the doodad.

Yup, this ones going to last a 'mill' oo0ps thousand years. Oh bugger we got
fucked over, shit.





Hey! folks. It's a new Millenium.......

And, just in case your thinking we're going to tell you that we sure aint
going to **** you over again... just don't forget that it's all worth 9.99
in the new currency.

DNA

Couldn't have said that better myself.

John
 
G

Genome

Jan 1, 1970
0
True, its a real pain fucking around with the locals, or at least some of them.

Dirk

Shit, I've only got two of the locals. I usually spend heavy time on the
primary and treat my locals real gentle whilst stroking the odd secondary.

You seem to have more locals than myself. I couldn't afford to waste one
because I'm not into that machocism type stuff and, I kind of assume, they
don't grow back too quickley.

I'd really like to know about your extra variables though.


DNA
 
D

Dirk Bruere at Neopax

Jan 1, 1970
0
Genome said:
Shit, I've only got two of the locals. I usually spend heavy time on the
primary and treat my locals real gentle whilst stroking the odd secondary.

You seem to have more locals than myself. I couldn't afford to waste one
because I'm not into that machocism type stuff and, I kind of assume, they
don't grow back too quickley.

I'd really like to know about your extra variables though.

Given the dia of coil is large eg >1m field strength at different points for
different power inputs (current) at various frequencies. Even the latter are not
well defined since they are pseudorandom pulse trains in the hundreds of Hz.
Then we have coil resistance, power handling, wire dia etc
Simplified somewhat given that I am assuming it will be driven by hi power audio
amps, so DC into 4 ohms is worst case.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org
 
G

Genome

Jan 1, 1970
0
Dirk Bruere at Neopax said:
Given the dia of coil is large eg >1m field strength at different points for
different power inputs (current) at various frequencies. Even the latter are not
well defined since they are pseudorandom pulse trains in the hundreds of Hz.
Then we have coil resistance, power handling, wire dia etc
Simplified somewhat given that I am assuming it will be driven by hi power audio
amps, so DC into 4 ohms is worst case.

Shit!

I was thinking about stroking my nipples or caressing my armpits a little
bit.

Hey.

I'm sure your right, if it works for you, but I don't think I'm ready for
the really esoteric stuff yet.

DNA
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Dirk Bruere at Neopax
How accurate is that?
Given, for example a coil with one metre dia and (say) 100 turns of #24?

It depends on exactly how compact you make the winding. It will
overestimate the inductance because the coupling between turns is not
100%. The advantage of it is that it is far simpler than the more
accurate formulae, and in practice you have to measure the finished coil
anyway.
Well, I suppose the centre might be a good starting point.
Typical coil dia would be around one metre.
Also two metres from centre in the plane of the coil.

OK. At the centre, the field strength H in amps per meter is I/d, where
I is the current in amps and d is the diameter of the coil. If you want
it in induction terms, 1 A/m = 1.26 microtesla in air.

On the axis of the coil and a distance h from its plane, the field
strength H is (Ir^2)/{2(r^2 + h^2)^(3/2)}.

Use Courier font for another way of writing that:

2
Ir
H = -------------
( 2 2)3/2
2(r + h )

I hope that's clear.
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Genome <[email protected]>
wrote (in <[email protected]>) about 'Coil formula',
The Aylward appears to have claimed to be a nigger, but he's an
export..... so he's not an Indian.

I think he has strong connections with the Indian sub-continent. He
isn't of African extraction, at least, no more than we all are. (;-)
 
A

Active8

Jan 1, 1970
0
Irish, German, dark rumors of a trace of French and possibly even a
bit of converted Jew somewhere.

I used to live on Highland Avenue

Balto? Highlandtown?
and decided to incorporate and my
expensive lawyer

Mine charged $75 to read my articles and give me an indemnity clause
for the bylaws. He also gave an opinion on the typical contract I
was used to entering into.
called me and asked for the company name to file the
papers, so I said you-know-what. Never paid him, come to think of it.

Our company logo depicts the view looking at Mount Tamalpias

That Mt oesn't ring a bell.
 
A

Active8

Jan 1, 1970
0

That right arrow at top goes to a really good work on designing
coils. It's had a face lift, also. The author had zipped the old
version of the pages up for me. I'm confused, though. The old set of
pages were under the CMU advisor section of the site, but now some
are at U of Surrey. The URL at CMU is different now and at first I
thought it was a rip-off. What's the relationship between CMU and U
of Surrey?
 
J

John Larkin

Jan 1, 1970
0
Balto? Highlandtown?

http://maps.yahoo.com/maps_result?e...csz=san+francisco&country=us&new=1&name=&qty=

It looks like a nice neighborhood. It's not. But I think the
bell-shaped streets are a visual pun; Mission Bells, the Bells of St
Mary's, something like that. There's lots of stuff like that around
here.
Mine charged $75 to read my articles and give me an indemnity clause
for the bylaws. He also gave an opinion on the typical contract I
was used to entering into.

We had certain hassles, and it cost me $5K or so. As I didn't have $5K
or so, he took stock. This is a *really nice* lawyer.


In Marin County, just north of San Francisco. Well worth a hike if
you're ever in the neighborhood. Giant redwoods and stuff.

John
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that John Larkin <jjSNIPlarkin@highTHIS
landPLEASEtechnology.XXX> wrote (in <jnavv0tl26o65j7jlq8598n4su532m0uul@
4ax.com>) about 'Coil formula', on Tue, 1 Feb 2005:
We had certain hassles, and it cost me $5K or so. As I didn't have $5K
or so, he took stock. This is a *really nice* lawyer.

What stock did you give him? Germanium transistors, selenium rectifiers
and carbon composition resistors? (;-)
 
A

Active8

Jan 1, 1970
0
I read in sci.electronics.design that John Larkin <jjSNIPlarkin@highTHIS
landPLEASEtechnology.XXX> wrote (in <jnavv0tl26o65j7jlq8598n4su532m0uul@
4ax.com>) about 'Coil formula', on Tue, 1 Feb 2005:

The others I called had a set basic price. No bargains. My first
accountant did 5 yrs of taxes for $50 per year. After I inc'd,
another one charged $450 for personal and corporate for one year.
What stock did you give him? Germanium transistors, selenium rectifiers
and carbon composition resistors? (;-)

I'd be interested to know just how nice he really was. Maybe your
biz plan and experience played a big factor in that. Risk reduction.
Sounds like you started on a shoestring budget.
 
L

lemonjuice

Jan 1, 1970
0
I read in sci.electronics.design that Dirk Bruere at Neopax

Inductance = 1.6 uH per metre of turn length, for one turn, if the
conductor diameter is much smaller than the coil diameter. For more
turns, if closely-coupled, multiply by the square of the number of
turns.
what the hell are you saying.

L = 0.394r^2 X N^2 / ( 9r + 10len )

where:
L = inductance in uH
r = coil radius in centimetres
N = number of turns
len = length of the coil in centimetres
At what point do you want to know the field strength? At an arbitrary
point, it involves elliptic functions, but some points are degenerate
and give simple results.
Elliptic functions ... oh gosh ... I can't stand this anymore.
 
J

John Larkin

Jan 1, 1970
0
The others I called had a set basic price. No bargains. My first
accountant did 5 yrs of taxes for $50 per year. After I inc'd,
another one charged $450 for personal and corporate for one year.

I'd be interested to know just how nice he really was. Maybe your
biz plan and experience played a big factor in that. Risk reduction.
Sounds like you started on a shoestring budget.

Yup. We had about $20,000 in savings and a steady stream of
unemployment checks. No business plan; they're nonsense.

We've given him a lot of business since then. We recently had a big
fight with another company owned by Sand Hill Road Leeches (ie,
nanotech venture capitalists). We settled for $80,000 cash (all of
which the lawyers got) and a heap of stock (probably worthless) and it
was great fun all around. If you are ever offered help from VCs and
help from the Devil, go with Satan.

But John M. is a rare, nice, thoughtful guy who keeps us out of
trouble. He only does business stuff and brings in the expensive hired
guns if litigation is involved. He talked a bunch to me about what I
really wanted in that situation, and what financial + psychic price I
was willing to pay to get it. If anybody needs a really good business
attorney in SF/Silicon Valley, let me know.

John
 
A

Active8

Jan 1, 1970
0
On Tue, 01 Feb 2005 20:22:19 -0800, John Larkin wrote:

Yup. We had about $20,000 in savings and a steady stream of
unemployment checks. No business plan; they're nonsense.

It's what investors want to see, from my reading. I take it you
didn't borrow any startup capital.

was great fun all around. If you are ever offered help from VCs and
help from the Devil, go with Satan.

LOL. You trusted people called Leeches and you have a bad taste in
your mouth? I've heard nothing negative about VCs until now. What's
the deal?

How do I get in touch with Satan if I need him? ;)

<snip>
 
J

John Larkin

Jan 1, 1970
0
On Tue, 01 Feb 2005 20:22:19 -0800, John Larkin wrote:



It's what investors want to see, from my reading. I take it you
didn't borrow any startup capital.



LOL. You trusted people called Leeches and you have a bad taste in
your mouth? I've heard nothing negative about VCs until now. What's
the deal?

No, I helped a company, a spinout of the University of Wisconsin, get
going. I designed a heap of electronics for them (they were materials
scientists, mostly) and the deal I had with the founder was that, if
the company was successful, they'd buy the electronics from us. The
electronics would have been just a couple percent of product (a $3
million electron microscope) cost. That was fair: free engineeering in
exchange for being preferred vendor for production. But the founder
spent money like a drunken sailor and burned up the 3F funding
(friends, family, fools) before he could sell anything and had to go
crawling to VCs to survive. Their contracts are a sight to behold:
they own *everything* and the founders and 3Fs get totally screwed.
And they wouldn't honor our deal. So we had a spat. Now I'm working
with their competitors, who are outselling them about 10:1.

Too bad; they were basicly nice people who made beginners mistakes and
had to sell their souls to vicious bastards. At our last meeting, in a
room full of laywers, the founder looked me in the face and lied.
There were too many knives at his back, too much at stake, for honor.

Moral: always own 51%.

John
 
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