Coil formula

Jan 31, 2005 17 Replies

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' INDUCTANCE OF CIRCULAR RING

' REF DATA P 6-9

CLS

TOP: INPUT "RING RADIUS, INCHES ", A IF A = 0 THEN GOTO EXX

PRINT

INPUT "WIRE DIA, INCHES ", D IF D = 0 THEN GOTO EXX

PRINT

L = (A / 100) * (7.353 * LOG(16 * A / D) / LOG(10) - 6.386)

PRINT USING "L = #####.##### uH"; L

PRINT PRINT GOTO TOP

EXX: END

================================================================

' PROGRAM : MAGFIELD.BAS ' BY : JENNIFER HO ' HIGHLAND TECNHOLOGY, INC. ' FEBRUARY 2, 1995

DEFDBL A-Z

CLS

PRINT "GIVEN A CIRCULAR LOOP OF RADIUS (R) CARRYING CURRENT (I)," PRINT "THIS PROGRAM CALCULATES THE MAGNETIC FIELD (B) AT ALL" PRINT "POINTS ON THE AXIS OF THIS LOOP, WHICH WE TAKE TO BE THE" PRINT "Z AXIS, WITH Z=0 AT THE LOOP CENTER." PRINT PRINT

INPUT "ENTER LOOP RADIUS (R) in Meters : ", R IF R = 0 THEN GOTO EXXON

INPUT "ENTER LOOP CURRENT (I) in Amperes : ", I

INPUT "ENTER THE DISTANCE (Z) ALONG THE AXIS in Meters : ", Z

'Uo IS IN THE UNIT OF "GAUSS METER / AMPERE".

Uo = 12.57 * 10 ^ -3

B = (Uo * I * R ^ 2) / (2 * SQR((Z ^ 2 + R ^ 2) ^ 3))

PRINT PRINT " ggg mmmuuunnn" PRINT USING "FIELD (B) in Gauss IS : ###.#########"; B

EXXON: END

=============================================================

' PROGRAM : MAGFIELD.BAS ' BY : JENNIFER HO ' HIGHLAND TECNHOLOGY, INC. ' FEBRUARY 2, 1995

DEFDBL A-Z

CLS

PRINT "GIVEN A CIRCULAR LOOP OF RADIUS (R) CARRYING CURRENT (I)," PRINT "THIS PROGRAM CALCULATES THE MAGNETIC FIELD (B) AT ALL" PRINT "POINTS ON THE AXIS OF THIS LOOP, WHICH WE TAKE TO BE THE" PRINT "Z AXIS, WITH Z=0 AT THE LOOP CENTER." PRINT PRINT

INPUT "ENTER LOOP RADIUS (R) in Meters : ", R IF R = 0 THEN GOTO EXXON

INPUT "ENTER LOOP CURRENT (I) in Amperes : ", I

INPUT "ENTER THE DISTANCE (Z) ALONG THE AXIS in Meters : ", Z

'Uo IS IN THE UNIT OF "GAUSS METER / AMPERE".

Uo = 12.57 * 10 ^ -3

B = (Uo * I * R ^ 2) / (2 * SQR((Z ^ 2 + R ^ 2) ^ 3))

PRINT PRINT " ggg mmmuuunnn" PRINT USING "FIELD (B) in Gauss IS : ###.#########"; B

EXXON: END

====================================

John

Oops, Jennifer's prog got pasted twice.

John

As the conductor diameter trends towards zero, the inductance becomes infinite.

John

It's 1/1000 of a lenium.

John

Sorry I'm not helping, except that, what is a millenium?

Ian Stirling, G4ICV, AB2GR, Long Valley, New Jersey, USA. Email address is not valid: contact details are on that domain's web site.

agreed, but what is a lenium? I know about lenniums.

Ian Stirling, G4ICV, AB2GR, Long Valley, New Jersey, USA. Email address is not valid: contact details are on that domain's web site.

LENIUM ES is a binary azeotrope of n-Propyl Bromide (nPB) and isopropanol expressly formulated to remove both polar and non-polar soils from circuit assemblies and components.

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Best regards, Spehro Pefhany

"it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com

Any got a pointer to the formula for inductance and field strength for a given current for a large dia air core coil? Dia>>length or winding thickness



thanks Dirk



The Consensus:- The political party for the new millenium

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strength for a given

thickness

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As a start. Not all you wanted, but a start!!!!

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Thanks, but I've already seen it. I was hoping for a 'finished' formula so I wouldn't have to spend a few hours messing around with stuff since I'll be juggling several other variables besides the obvious ones. Actually, a better version of the above is here:

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

I read in sci.electronics.design that Dirk Bruere at Neopax wrote (in ) about 'Coil formula', on Sun, 30 Jan 2005:

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.

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.

Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

How accurate is that? Given, for example a coil with one metre dia and (say) 100 turns of #24?

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.

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

Thanks. Interesting as I am going to write a Java applet to do something similar.

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

Its like 'millennium' but shorter. A bit like 'It's' without an apostrophe.

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

I read in sci.electronics.design that Dirk Bruere at Neopax wrote (in ) about 'Coil formula', on Mon, 31 Jan 2005:

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.

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.

Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Donna and Ian wrote (in ) about 'Coil formula', on Sun, 30 Jan 2005:

A thousad years, of course. (;-)

-- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited.

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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?

Best Regards, Mike

for a given

thickness

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

Elliptic functions ... oh gosh ... I can't stand this anymore.

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