Inductor Multi-Tap Calcualtor

A free, open-source tool for apportioning taps on an inductor.

 home: ky8d.net/free 

Introduction    ↑   → 

A free-running calculator for ratiometrically locating taps on an inductor. One with which you can haggle to get exactlty just what you want. And do it without tediously enduring a series of one-shot do-overs.

List of Features     ←   ↑   → 

• Calculates total inductance.
• Choose single or multiple cores.
• Choose any number of taps.
• Choose linear or geometrically proportional spacing.
• Choose minimum value of 1st tap.
• Constrain tap-locations as whole or fractional turns.
  • Allows odd-number fractions to support basketweave coils.
• Get tap locations and their inductance values.

Measureing A_L     ←   ↑   → 

My LabVIEW calculator will only be as accurate as the AL value which you provide it. Many a toroid have tolerances of ±25%.

Above you see the example of Fair-Rite model l5968003801, whose AL lists as minimum 16nH/turn. Directly measuring 50 turns at 10kHz with an LCR Meter, I find it to have actually 18.2nH/turn.

Haggling     ←   ↑   → 

You may need to haggle to get exactly just what you want. In the screenshot at top, my design constraints were as below:

• Min value: 250nH
• Max value: 50uH
• Taps: 38
  • Because of having a 2-deck, 20-pos switch (19 plus off).
  • The above in combination with an SPDT switch for High/Low ranges.

And, as you can see, I obtained those values very closely indeed. And with the taps spaced both ratiometrically, (as only makes sense), and also conveniently (always at an easily identifiable cross-sectional flat or corner).

The haggling steps went as follows...

1. I entered the AL got by measuring my toroid of choice.
2. I adjusted the Turns (N) control until the readout L (H) showed just above 50u.
3. I entered 34 as my desired number of taps.
4. I saw that the readout Taps (N) agreed, showing 34.
5. I saw also that Tap 1 at 1.125 turns gave only 23.034n.
   • Much too small to be of use.
6. So I set Min (H) for 250n.
   • Which caused the readout Taps (N) to fall short of 34.
   • So that it turned red and started to blink, because of not agreeing with the control likewise named Taps (N). As it will continue to do from this point on, but which I will ignore.
7. Next I raised the taps target in the control Taps (N) until the readout Taps (N) showed 34.
   • Which caused a minor upset to the inductance of first tap.
8. Repeating the prior two numbered steps a couple times more got things just right.

Download     ←   ↑ 

You’ll need two things for it to run: my *.exe application itself, plus also the interpreter program on which it runs. Kind of like Java that way, except that the Java interpreter is probably pre-installed on your system. The LabVIEW run-time engine will not be.

1.  LabVIEW Runtime Engine 
   • This is the interpretor program.
   • Or, should it please you, the entire LabVIEW programming environment.
   • Link back to ky8d.net/free where I give download instructions.
2.  KY8D_Inductor_Multi-Tap_Calculator.exe 
3. Unzips as a *.exe file. Employ a stand-alone ZIP archive software (like  7-Zip ) for the extraction.
4. Source Code, for any who want it.
   • Here too is my source code to do with just as you please. And although I will take it very kindly if given credit, I do not insist you must do so.
   •  Source  The LabVIEW source code.