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2nd August 2013, 04:50 AM  #1 
diyAudio Member
Join Date: Jul 2013

Inductor Computation
Hello There,
Could Anyone please show me how to make inductors and computations? 
2nd August 2013, 06:04 AM  #2 
diyAudio Member
Join Date: Nov 2011
Location: UK

Could you please expand on what you are trying to make ? There are inductors and there are INDUCTORS.
The requirements of a crossover inductor are very different to a choke for a power supply for example. 
2nd August 2013, 06:11 AM  #3 
diyAudio Member
Join Date: Jul 2013

im sorry, but its air core inductor for power amp output. thanks

2nd August 2013, 01:24 PM  #4 
diyAudio Member
Join Date: Nov 2011
Location: UK

Try Googling  Wheeler's Formula.

7th August 2013, 12:55 PM  #5 
diyAudio Member

I used this formula for aircore coils from the 1936 Edition of Electrical Engineers' Handbook (Pender Mcilwain). A scan of the page is attached below.
If you have a way to run GWBasic in your PC you can use the following BASIC program which I wrote in early nineties to compute the number of turns, length and weight of the copper wire you need. Fairly accurate. (You have to input the diameter of the wire in inches, taken from a SWG or AWG table). Eg., SWG18 is 0.048 inches dia., which is the default if you don't input a value. ************************************************** ******** 300 INPUT "INDUCTANCE (MICRO H)?", LR 310 INPUT "Wire diameter(inches)?",D 320 IF D=0 THEN D=.048: PRINT "WIRE 18 SWG (DIA=.048 INCH)" 330 NL=1 340 REM D1=DIA OF FORMER 350 PRINT "DIAMETER OF FORMER, IN INCHES (DEFAULT: 1 INCH.)"; 360 INPUT D1 365 IF D1=0 THEN D1=1 370 REM B=LENGTH OF WINDING 380 PRINT "LENGTH OF COIL, IN INCHES (DEFAULT: 1 INCH.)"; 390 INPUT B 395 IF B=0 THEN B=1 400 R=D1/2 410 REM A=MEAN RADIUS OF COIL 420 A=R+((NL*D)/2) 430 REM c=depth of winding 440 C=NL*D 450 N=NL*(1/(D+.001))*B 460 L=(.8*(A^2)*(N^2))/((6*A)+(9*B)+(10*C)) 470 GOTO 620 480 NL=NL+1 490 IF L>=LR GOTO 510 500 GOTO 400 510 N1=SQR((LR*((6*A)+(9*B)+(10*C)))/(.8*(A^2))) 520 PRINT INT(N1+.5);"turns" 530 PRINT"depth of winding=";C;"inch 540 PRINT "length of wire=";TL;" inches" 550 REM METRIC CONV. 560 RM=(D/2)*2.54 570 TLM=TL*2.54 580 VOLM=PI*(RM^2)*TLM 585 REM Specific gravity of copper=8.92 590 WC=VOLM*8.92 600 PRINT "weight of copper=";WC;"gms" 610 END 620 REM 630 PI=3.1416 640 R1 = R +(D*NL)(D/2) 650 LC= 2*PI*R1 660 LL=LC*(B/D) 670 TL= TL +LL 680 GOTO 480 *********************************************** John
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