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<!DOCTYPE html>
< html lang = "en" >
< head >
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< title > VK3CPU RF Inductor Calculator< / title >
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< link rel = "stylesheet" href = "inductor.css" >
< / head >
< body >
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< header > Miguel < a href = "mailto:vk3cpu@gmail.com" > VK3CPU< / a > - RF Inductor Calculator v0.8< / header >
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< section class = "gridLayoutClass" >
< div id = "inductor-container" class = "inductor-container" style = "position: relative;" >
< canvas id = "inductor2D" class = "inductorClass" width = "350" height = "350" >
< / canvas >
< / div >
< div class = "slider_container" >
< div class = "sliders" >
< label for = "conductor_diameter_slider" > & #8960a:< / label >
< input type = "range" id = "conductor_diameter_slider" min = "0.1" max = "5.0" value = "1.0" step = "0.05" >
< / div >
< div class = "sliders" >
< label for = "loop_diameter_slider" > & #8960b:< / label >
< input type = "range" id = "loop_diameter_slider" min = "5.0" max = "50.0" value = "10.0" step = "0.1" >
< / div >
< div class = "sliders" >
< label for = "loop_spacing_slider" > c/a:< / label >
< input type = "range" id = "loop_spacing_slider" min = "1.1" max = "4.0" value = "2.0" step = "0.01" >
< / div >
< div class = "sliders" >
< label for = "loop_turns_slider" > N:< / label >
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< input type = "range" id = "loop_turns_slider" min = "2" max = "100" value = "4.0" step = "1.0" >
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< / div >
< div class = "sliders" >
< label for = "frequency_slider" > f:< / label >
< input type = "range" id = "frequency_slider" min = "1.0" max = "30.0" value = "7.0" step = "0.1" >
< / div >
< / div >
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< br >
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< b > < u > Notes:< / u > < / b > < br >
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RF Inductor Designer was developed to help users predict the RF characteristics of a single-layer solenoid-style air-core inductor. < br > < br >
< u > Inputs via the slider widgets:< / u >
< ul >
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< li > & #8960a : Conductor diameter in millimeters (mm). Estimated equivalent AWG wire size is also displayed where appropriate.< / li >
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< li > & #8960b : Loop diameter in millimeters (mm).< / li >
< li > c/a : 'c' is the inter-winding spacing, and 'a' is the conductor diameter, so 'c/a' is the spacing ratio. (Must be >= 1.1)
A low-value will increase the proximity effect.< / li >
< li > N : Number of turns or windings.< / li >
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< li > f : The frequency of interest (MHz) for some of the calculations.< / li >
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< / ul >
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< p > Characteristics on the left are independent of frequency, while the characteristics on the right are dependent on the selected frequency. < br > < br >
Each of the graphic representations attempt to keep the relative geometry correct, without exceeding the drawing boundary. The coil diameter
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relative to the conductor diameter are representative. < / p >
< u > Calculated dimensions:< / u >
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< ul >
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< li > & #8960o : Outer loop diameter (mm) < / li >
< li > & #8960i : Inner loop diameter (mm) - corresponds to the diameter of the winding former.< / li >
< li > c : Distance between windings, measured from the conductor centers (mm).< / li >
< li > & #8467 : Length of the coil (mm). Equal to c x N.< / li >
< / ul >
< u > Calculated parameters:< / u >
< ul >
< li > L : Inductance is calculated using an equation incorporating the Nagaoka coefficient.< / li >
< li > C : Capacitance is calculated using Knight's 2016 paper on self-resonance and self-capacitance of solenoid coils.< / li >
< li > Rdc : DC resistance is calculated using conductor length divided by the conductor cross-sectional area, assuming a copper conductor.< / li >
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< li > SRF : Self-resonant frequency (MHz) for the unloaded coil. Currently using a lumped reactances model. (Looking into modifying the model to
use the conductor length and velocity factor as described by Knight (2016).< / li >
< li > Xl : Inductive reactance at the given frequency. (& #937)< / li >
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< li > & #948 : Skin depth due to skin effect (& #956m)< / li >
< li > Rac : AC resistance is calculated using the skin effect and proximity resistance from empirical data collected by Medhurst using the spacing ratio, and length-to-diameter ratio.< / li >
< li > Q : Quality factor of device, based on reactance (X) & #247 resistance (Rac) at the given frequency.< / li >
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< / ul >
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< / section >
< script src = "https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js" > < / script >
< script src = "https://cdn.jsdelivr.net/npm/chartjs-plugin-crosshair@1.1.2" > < / script >
< script >
var loop_diameter_slider = document.getElementById("loop_diameter_slider");
var loop_diameter_value = document.getElementById("loop_diameter_value");
var val = loop_diameter_slider.value * 1.0;
var conductor_diameter_slider = document.getElementById("conductor_diameter_slider");
var conductor_diameter_value = document.getElementById("conductor_diameter_value");
var loop_turns_slider = document.getElementById("loop_turns_slider");
var loop_turns_value = document.getElementById("loop_turns_value");
var loop_spacing_slider = document.getElementById("loop_spacing_slider");
var loop_spacing_value = document.getElementById("loop_spacing_value");
val = loop_spacing_slider.value * 1.0;
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// Global constants:
const mu0 = Math.PI * 4e-7;
const cu_sigma = 58e6; // Copper conductance value
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function dcResistance() {
const loop_diameter_meters = 1e-3 * loop_diameter_slider.value;
const cond_diameter_meters = 1e-3 * conductor_diameter_slider.value;
const cond_radius_meters = 0.5 * cond_diameter_meters;
const c_spacing = loop_spacing_slider.value * cond_diameter_meters;
const corr_factor = Math.sqrt(1.0 + (c_spacing**2 / loop_diameter_meters**2));
const conductor_length = Math.PI * loop_diameter_meters * loop_turns_slider.value * corr_factor;
const conductor_area = Math.PI * (cond_radius_meters**2.0);
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//console.log(conductor_length, conductor_area);
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return 1.68e-8 * conductor_length / conductor_area;
}
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function skinDepth() {
return Math.sqrt(1.0 / (Math.PI * frequency_slider.value * 1e6 * mu0 * cu_sigma));
}
// From Knight "Solenoid Impedance and Q"
function dc2acFactor() {
const diameter = 1e-3 * conductor_diameter_slider.value;
const skin_depth = skinDepth();
return diameter**2 / (4.0 * (diameter * skin_depth - skin_depth**2));
}
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function getInductance() {
const a_coil_radius = loop_diameter_slider.value * 0.0005;
const b_conductor_radius = conductor_diameter_slider.value * 0.0005;
const n_turns = 1.0 * loop_turns_slider.value;
const coil_length = b_conductor_radius * 2.0 * loop_spacing_slider.value * n_turns;
var retval = (n_turns**2.0) * mu0 * Math.PI * (a_coil_radius**2.0) * nagaokaCoefficient() / coil_length;
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return retval; // In Henries
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}
function inductiveReactance(frequency) {
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return 2.0 * Math.PI * frequency * getInductance(); // In Ohms
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}
function nagaokaCoefficient() {
// From Knight's 2016 paper on coil self-resonance, attributed to Wheeler's 1982 eqn as modified by Bob Weaver
const loop_diameter_meters = 1e-3 * loop_diameter_slider.value;
const cond_diameter_meters = 1e-3 * conductor_diameter_slider.value;
const c_spacing = loop_spacing_slider.value * cond_diameter_meters;
const x = loop_diameter_meters / (c_spacing * loop_turns_slider.value);
const zk = 2.0 / (Math.PI * x);
const k0 = 1.0 / (Math.log(8.0 / Math.PI) - 0.5);
const k2 = 24.0 / (3.0 * Math.PI**2 - 16.0);
const w = -0.47 / (0.755 + x)**1.44;
const p = k0 + 3.437/x + k2/x**2 + w;
var retval = zk * (Math.log(1 + 1/zk) + 1/p);
return retval;
}
function ctdw(ff, ei, ex) {
// From Knight's 2016 paper
const kL = nagaokaCoefficient();
const kct = 1.0/kL - 1.0;
return 11.27350207 * ex * ff * (1.0 + kct * (1.0 + ei/ex) / 2.0);
}
function ciae(ff, ei, ex) {
// From Knight's 2016 paper
return 17.70837564 * (ei+ex) / Math.log(1.0 + Math.PI**2 * ff);
}
function multiloopCapacitance() {
const loop_diameter_meters = 1e-3 * loop_diameter_slider.value;
const cond_diameter_meters = 1e-3 * conductor_diameter_slider.value;
const e0 = 8.854187e-12;
const h = 1.0 * loop_spacing_slider.value * cond_diameter_meters;
const ei = 1.0; // Assume internal epsilon is air (or free-space)
const ex = 1.0; // Assume external epsilon is air (or free-space)
const solenoid_length = 1.0 * loop_turns_slider.value * h;
const ff = solenoid_length / loop_diameter_meters;
var multiloop_capacitance = 1e-12 * (ctdw(ff, ei, ex) / Math.sqrt(1 - h**2 / loop_diameter_meters**2) + ciae(ff, ei, ex)) * loop_diameter_meters;
return multiloop_capacitance; // in Farads
}
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const proximityResistance = [
// From R.G. Medhurst H.F. Resistance and Self-Capacitance of Single-Layer Solenoids (Feb, 1947)
[ 0.0, 1.0, 1.111, 1.25, 1.429, 1.667, 2.0, 2.5, 3.333, 5.00, 10.0 ],
[ 0.0, 5.31, 3.73, 2.74, 2.12, 1.74, 1.44, 1.20, 1.16, 1.07, 1.02 ],
[ 0.2, 5.45, 3.84, 2.83, 2.20, 1.77, 1.48, 1.29, 1.19, 1.08, 1.02 ],
[ 0.4, 5.65, 3.99, 2.97, 2.28, 1.83, 1.54, 1.33, 1.21, 1.08, 1.03 ],
[ 0.6, 5.80, 4.11, 3.10, 2.38, 1.89, 1.60, 1.38, 1.22, 1.10, 1.03 ],
[ 0.8, 5.80, 4.17, 3.20, 2.44, 1.92, 1.64, 1.42, 1.23, 1.10, 1.03 ],
[ 1.0, 5.55, 4.10, 3.17, 2.47, 1.94, 1.67, 1.45, 1.24, 1.10, 1.03 ],
[ 2.0, 4.10, 3.36, 2.74, 2.32, 1.98, 1.74, 1.50, 1.28, 1.13, 1.04 ],
[ 4.0, 3.54, 3.05, 2.60, 2.27, 2.01, 1.78, 1.54, 1.32, 1.15, 1.04 ],
[ 6.0, 3.31, 2.92, 2.60, 2.29, 2.03, 1.80, 1.56, 1.34, 1.16, 1.04 ],
[ 8.0, 3.20, 2.90, 2.62, 2.34, 2.08, 1.81, 1.57, 1.34, 1.165, 1.04],
[ 10.0, 3.23, 2.93, 2.65, 2.37, 2.10, 1.83, 1.58, 1.35, 1.17, 1.04 ],
[999.0, 3.41, 3.11, 2.815, 2.51, 2.22, 1.93, 1.65, 1.395, 1.19, 1.05]
];
function getProximityResFromSpacing() {
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// Use the proximityResistance look-up table and interpolate values depending on the spacing ratio and the number of turns.
var retval = 0.0;
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const n_turns = 1.0 * loop_turns_slider.value;
const spacing_ratio = 1.0 * loop_spacing_slider.value;
const length_diameter_ratio = n_turns * spacing_ratio * conductor_diameter_slider.value / loop_diameter_slider.value;
var i = 0; // Going to the right, which is the spacing ratio
var j = 0; // Going down the page, which is the solenoid length to diameter ratio
for (i = 1; i < (proximityResistance[0].length); i++) {
if(spacing_ratio < proximityResistance [ 0 ] [ i ] ) {
i--;
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break;
}
}
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for (j = 1; j < (proximityResistance.length); j++) {
if(length_diameter_ratio < proximityResistance [ j ] [ 0 ] ) {
j--;
break;
}
}
var t1 = ((spacing_ratio - proximityResistance[0][i]) / (proximityResistance[0][i+1] - proximityResistance[0][i])) * (proximityResistance[j][i+1] - proximityResistance[j][i]) + proximityResistance[j][i];
var t2 = ((spacing_ratio - proximityResistance[0][i]) / (proximityResistance[0][i+1] - proximityResistance[0][i])) * (proximityResistance[j+1][i+1] - proximityResistance[j+1][i]) + proximityResistance[j+1][i];
retval = ((length_diameter_ratio - proximityResistance[j][0])/(proximityResistance[j+1][0] - proximityResistance[j][0])) * (t2 - t1) + t1;
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return retval;
}
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function acResistance() {
const Rdc = dcResistance();
const dc2ac = dc2acFactor();
const prox = getProximityResFromSpacing();
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// console.log(Rdc, dc2ac, prox);
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return Rdc * dc2ac * prox;
}
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function qualityFactor(frequency) {
const Xl = inductiveReactance(frequency);
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const Rac = acResistance();
const Q = Xl / Rac;
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return Q;
}
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function selfResonantFrequency() {
var freq = 1.0 / (2.0 * Math.PI * Math.sqrt(getInductance() * multiloopCapacitance()));
return freq;
}
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loop_diameter_slider.oninput = function() {
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drawDesign();
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}
conductor_diameter_slider.oninput = function() {
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drawDesign();
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}
loop_turns_slider.oninput = function() {
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drawDesign();
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}
loop_spacing_slider.oninput = function() {
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drawDesign();
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}
frequency_slider.oninput = function() {
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drawDesign();
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}
window.onresize = function() {
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drawDesign();
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}
window.onorientationchange = function() {
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drawDesign();
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}
window.onbeforeprint = function() {
console.log("onbeforeprint");
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drawDesign();
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}
const afront_canvas = document.getElementById("inductor2D");
const fctx = afront_canvas.getContext('2d');
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function drawDesign() {
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const win_width = document.getElementById("inductor-container").clientWidth;
const win_height = document.getElementById("inductor-container").clientHeight;
afront_canvas.width = win_width-12;
afront_canvas.height = win_height-12;
fctx.clearRect(0, 0, win_width, win_height);
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const loop_radius = 0.14 * win_height; // 100; // loop_diameter_slider.value * 80;
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var cond_radius = loop_radius * conductor_diameter_slider.value / loop_diameter_slider.value;
const loopx = win_width/2;
const loopy = win_height/4;
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// Draw loop ends first, then draw the loop after:
fctx.strokeStyle = "grey";
fctx.beginPath();
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fctx.arc(loopx - 0.5*loop_radius, loopy + 1.414*loop_radius, 0.5 * loop_radius, 0.0, -0.40 * Math.PI, true);
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fctx.lineWidth = cond_radius * 2.0;
fctx.stroke();
fctx.strokeStyle = "black";
fctx.beginPath();
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fctx.arc(loopx + 0.5*loop_radius, loopy + 1.414*loop_radius, 0.5 * loop_radius, Math.PI, -0.60 * Math.PI, false);
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fctx.lineWidth = cond_radius * 2.0;
fctx.stroke();
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// Draw loop:
fctx.beginPath();
fctx.arc(loopx, loopy, loop_radius, 0.0, 2.0 * Math.PI, false);
fctx.stroke();
fctx.lineWidth = 1.0;
// Draw loop diameter arrow:
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const y_offset = loopy + loop_radius + 20;
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var arrow_size = 10.0;
fctx.beginPath();
fctx.moveTo(loopx - loop_radius, loopy);
fctx.lineTo(loopx - loop_radius, y_offset);
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fctx.lineTo(loopx - loop_radius - arrow_size, y_offset - arrow_size);
fctx.lineTo(loopx - loop_radius - arrow_size, y_offset + arrow_size);
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fctx.lineTo(loopx - loop_radius, y_offset);
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fctx.lineTo(loopx - loop_radius - 3.0*arrow_size, y_offset);
fctx.stroke();
fctx.beginPath();
fctx.moveTo(loopx + loop_radius, loopy);
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fctx.lineTo(loopx + loop_radius, y_offset);
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fctx.lineTo(loopx + loop_radius + arrow_size, y_offset - arrow_size);
fctx.lineTo(loopx + loop_radius + arrow_size, y_offset + arrow_size);
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fctx.lineTo(loopx + loop_radius, y_offset);
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fctx.lineTo(loopx + loop_radius + 3.0*arrow_size, y_offset);
fctx.stroke();
// Write loop diameter symbol:
fctx.font = "12px arial";
fctx.textAlign = "right";
const dia = 1.0 * loop_diameter_slider.value;
fctx.fillText("\u2300b = " + dia.toPrecision(3).toString() + "mm", loopx - loop_radius - 2.0*arrow_size, y_offset - 2);
// Draw inner-diameter arrows: (for using a winding former)
const inner_dia_y = loopy + loop_radius + 40;
fctx.beginPath();
fctx.moveTo(loopx - loop_radius + cond_radius, loopy);
fctx.lineTo(loopx - loop_radius + cond_radius, inner_dia_y);
fctx.lineTo(loopx - loop_radius + cond_radius - arrow_size, inner_dia_y - arrow_size);
fctx.lineTo(loopx - loop_radius + cond_radius - arrow_size, inner_dia_y + arrow_size);
fctx.lineTo(loopx - loop_radius + cond_radius, inner_dia_y);
fctx.lineTo(loopx - loop_radius - 3.0*arrow_size, inner_dia_y);
fctx.stroke();
fctx.beginPath();
fctx.moveTo(loopx + loop_radius - cond_radius, loopy);
fctx.lineTo(loopx + loop_radius - cond_radius, inner_dia_y);
fctx.lineTo(loopx + loop_radius - cond_radius + arrow_size, inner_dia_y - arrow_size);
fctx.lineTo(loopx + loop_radius - cond_radius + arrow_size, inner_dia_y + arrow_size);
fctx.lineTo(loopx + loop_radius - cond_radius, inner_dia_y);
fctx.lineTo(loopx + loop_radius + 3.0*arrow_size, inner_dia_y);
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fctx.stroke();
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fctx.textAlign = "left";
fctx.fillText("\u2300i = " + (dia-1.0*conductor_diameter_slider.value).toPrecision(3).toString() + "mm", loopx + loop_radius + 2.0*arrow_size, inner_dia_y - 2);
// Draw outer-diameter arrows: (for using a winding former)
const outer_dia_y = loopy + loop_radius + 0;
fctx.beginPath();
fctx.moveTo(loopx - loop_radius - cond_radius, loopy);
fctx.lineTo(loopx - loop_radius - cond_radius, outer_dia_y);
fctx.lineTo(loopx - loop_radius - cond_radius - arrow_size, outer_dia_y - arrow_size);
fctx.lineTo(loopx - loop_radius - cond_radius - arrow_size, outer_dia_y + arrow_size);
fctx.lineTo(loopx - loop_radius - cond_radius, outer_dia_y);
fctx.lineTo(loopx - loop_radius - 3.0*arrow_size, outer_dia_y);
fctx.stroke();
fctx.beginPath();
fctx.moveTo(loopx + loop_radius + cond_radius, loopy);
fctx.lineTo(loopx + loop_radius + cond_radius, outer_dia_y);
fctx.lineTo(loopx + loop_radius + cond_radius + arrow_size, outer_dia_y - arrow_size);
fctx.lineTo(loopx + loop_radius + cond_radius + arrow_size, outer_dia_y + arrow_size);
fctx.lineTo(loopx + loop_radius + cond_radius, outer_dia_y);
fctx.lineTo(loopx + loop_radius + 3.0*arrow_size, outer_dia_y);
fctx.stroke();
fctx.fillText("\u2300o = " + (dia+1.0*conductor_diameter_slider.value).toPrecision(3).toString() + "mm", loopx + loop_radius + 2.0*arrow_size, outer_dia_y - 2);
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// Write loop inductance:
fctx.font = "12px arial";
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fctx.textAlign = "left";
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const L = getInductance() * 1.0e+6;
fctx.fillText("L = " + L.toPrecision(3).toString() + " \u03bcH", 8, 18);
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fctx.fillText("C = " + (multiloopCapacitance()*1e12).toFixed(1) + " pF", 8, 32);
fctx.fillText("Rdc = " + dcResistance().toFixed(2) + " \u03A9", 8, 46);
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fctx.fillText("SRF = " + (selfResonantFrequency()*1e-6).toFixed(1) + " MHz", 8, 60);
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// Draw conductor diameter arrow:
fctx.beginPath();
fctx.moveTo(loopx + loop_radius - cond_radius, loopy);
fctx.lineTo(loopx + loop_radius - cond_radius - arrow_size, loopy - arrow_size);
fctx.lineTo(loopx + loop_radius - cond_radius - arrow_size, loopy + arrow_size);
fctx.lineTo(loopx + loop_radius - cond_radius, loopy);
fctx.lineTo(loopx - 0.6*loop_radius, loopy);
fctx.stroke();
fctx.beginPath();
fctx.moveTo(loopx + loop_radius + cond_radius, loopy);
fctx.lineTo(loopx + loop_radius + cond_radius + arrow_size, loopy - arrow_size);
fctx.lineTo(loopx + loop_radius + cond_radius + arrow_size, loopy + arrow_size);
fctx.lineTo(loopx + loop_radius + cond_radius, loopy);
fctx.lineTo(loopx + loop_radius + cond_radius + 2.0*arrow_size, loopy);
fctx.stroke();
//fctx.textAlign = "right";
const cond_dia = 1.0 * conductor_diameter_slider.value;
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fctx.textAlign = "center";
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fctx.fillText("\u2300a = " + cond_dia.toPrecision(3).toString() + "mm", loopx, loopy - 6);
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var awg = "";
switch(cond_dia) {
case 0.100 :
awg = "~38 AWG";
break;
case 0.150 :
awg = "~35 AWG";
break;
case 0.200 :
awg = "~32 AWG";
break;
case 0.250 :
awg = "~30 AWG";
break;
case 0.300 :
awg = "~29 AWG";
break;
case 0.350 :
awg = "~27 AWG";
break;
case 0.400 :
awg = "~26 AWG";
break;
case 0.450 :
awg = "~25 AWG";
break;
case 0.500 :
awg = "~24 AWG";
break;
case 0.550 :
awg = "~23 AWG";
break;
case 0.650 :
awg = "~22 AWG";
break;
case 0.700 :
awg = "~21 AWG";
break;
case 0.800 :
awg = "~20 AWG";
break;
case 0.900 :
awg = "~19 AWG";
break;
case 1.00 :
awg = "~18 AWG";
break;
case 1.15 :
awg = "~17 AWG";
break;
case 1.30 :
awg = "~16 AWG";
break;
case 1.45 :
awg = "~15 AWG";
break;
case 1.55 :
awg = "~14 AWG";
break;
case 1.80 :
awg = "~13 AWG";
break;
case 2.00 :
awg = "~12 AWG";
break;
case 2.30 :
awg = "~11 AWG";
break;
case 2.60 :
awg = "~10 AWG";
break;
case 2.90 :
awg = "~9 AWG";
break;
case 3.25 :
awg = "~8 AWG";
break;
case 3.65 :
awg = "~7 AWG";
break;
case 4.10 :
awg = "~6 AWG";
break;
case 4.60 :
awg = "~5 AWG";
break;
}
fctx.textAlign = "left";
fctx.fillText(awg, loopx + loop_radius + cond_radius + 2.0*arrow_size, loopy - 6);
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var cond_spacing = 2.0 * cond_radius * loop_spacing_slider.value;
if((cond_spacing * loop_turns_slider.value) > (0.8 * win_width)) {
cond_radius = ((0.8 * win_width) / (loop_turns_slider.value * 2.0*loop_spacing_slider.value));
cond_spacing = 2.0 * cond_radius * loop_spacing_slider.value;
}
var start_x = win_width/2.0 - loop_turns_slider.value * cond_spacing * 0.5;
var top_y = win_height * 0.60;
var bot_y = top_y + cond_radius * (loop_diameter_slider.value / conductor_diameter_slider.value);
for (let i = 0; i < loop_turns_slider.value ; i + + ) {
fctx.beginPath();
fctx.moveTo(start_x + ((0.5 + i) * cond_spacing) + cond_radius, top_y);
fctx.lineTo(start_x + (i+1) * cond_spacing + cond_radius, bot_y);
fctx.arc(start_x + (i+1) * cond_spacing, bot_y, cond_radius, 0, Math.PI, false);
fctx.lineTo(start_x + ((0.5 + i) * cond_spacing) - cond_radius, top_y);
fctx.fillStyle = "grey";
fctx.fill();
fctx.beginPath();
fctx.arc(start_x + (i * cond_spacing), bot_y, cond_radius, 0, Math.PI);
fctx.arc(start_x + (cond_spacing * 0.5) + i * cond_spacing, top_y, cond_radius, Math.PI, 0);
fctx.lineTo(start_x + (i * cond_spacing) + cond_radius, bot_y);
fctx.closePath();
fctx.fillStyle = "black";
fctx.fill();
}
// Draw the wire ends:
fctx.fillRect(start_x - cond_radius, bot_y, 2.0 * cond_radius, 30);
fctx.fillStyle = "grey";
fctx.fillRect(start_x + loop_turns_slider.value*cond_spacing - cond_radius, bot_y, 2.0 * cond_radius, 30);
fctx.fillStyle = "black";
// Draw left spacing arrow:
const dim_y = win_height * 0.90;
fctx.beginPath();
fctx.moveTo(start_x - 20, dim_y);
fctx.lineTo(start_x, dim_y);
fctx.lineTo(start_x - 7, dim_y + 7)
fctx.lineTo(start_x - 7, dim_y - 7)
fctx.lineTo(start_x, dim_y);
fctx.moveTo(start_x, dim_y - 7);
fctx.lineTo(start_x, dim_y + 7);
fctx.stroke();
// Draw right spacing arrow:
fctx.beginPath();
fctx.moveTo(start_x + cond_spacing + 20, dim_y);
fctx.lineTo(start_x + cond_spacing, dim_y);
fctx.lineTo(start_x + cond_spacing + 7, dim_y + 7)
fctx.lineTo(start_x + cond_spacing + 7, dim_y - 7)
fctx.lineTo(start_x + cond_spacing, dim_y);
fctx.moveTo(start_x + cond_spacing, dim_y - 7);
fctx.lineTo(start_x + cond_spacing, dim_y + 7);
fctx.stroke();
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// Draw right length arrow:
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fctx.beginPath();
fctx.moveTo(start_x + loop_turns_slider.value*cond_spacing + 20, dim_y);
fctx.lineTo(start_x + loop_turns_slider.value*cond_spacing, dim_y);
fctx.lineTo(start_x + loop_turns_slider.value*cond_spacing + 7, dim_y + 7)
fctx.lineTo(start_x + loop_turns_slider.value*cond_spacing + 7, dim_y - 7)
fctx.lineTo(start_x + loop_turns_slider.value*cond_spacing, dim_y);
fctx.moveTo(start_x + loop_turns_slider.value*cond_spacing, dim_y - 7);
fctx.lineTo(start_x + loop_turns_slider.value*cond_spacing, dim_y + 7);
fctx.stroke();
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// Extended lines:
fctx.strokeStyle = "grey";
fctx.beginPath();
fctx.moveTo(start_x, bot_y + 35);
fctx.lineTo(start_x, dim_y - 12);
fctx.moveTo(start_x + cond_spacing, bot_y + 15);
fctx.lineTo(start_x + cond_spacing, dim_y - 12);
fctx.moveTo(start_x + loop_turns_slider.value*cond_spacing, bot_y + 35);
fctx.lineTo(start_x + loop_turns_slider.value*cond_spacing, dim_y - 12);
fctx.stroke();
fctx.strokeStyle = "black";
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fctx.font = "12px arial";
fctx.textAlign = "right";
var freq = 1.0 * frequency_slider.value;
fctx.fillText("f = " + freq.toFixed(1) + " MHz", win_width-18, 18);
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fctx.fillText("Xl = " + inductiveReactance(freq * 1e6).toFixed(1) + " \u03A9", win_width-18, 32);
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fctx.fillText("\u03B4 = " + (skinDepth() * 1e6).toFixed(1) + " \u03BCm", win_width-18, 46);
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fctx.fillText("Rac = " + acResistance(freq * 1e6).toFixed(2) + " \u03A9", win_width-18, 60);
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fctx.fillText("Q = " + qualityFactor(freq * 1e6).toFixed(1), win_width-18, 74);
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fctx.textAlign = "center";
fctx.fillText("N = " + loop_turns_slider.value.toString(), win_width/2, win_height * 0.56);
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// Draw spacing text: (gap is to avoid collision of spacing and length texts)
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fctx.textAlign = "right";
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var gap = ((loop_turns_slider.value*cond_spacing - cond_spacing) < 60 ) ? ( 60 - ( loop_turns_slider . value * cond_spacing - cond_spacing ) ) : 0 ;
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const spc = loop_spacing_slider.value * conductor_diameter_slider.value;
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fctx.fillText("c = " + spc.toFixed(1).toString() + "mm", start_x + cond_spacing + 20 - gap, dim_y + 20);
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// Draw length text:
const sol_len = loop_turns_slider.value*spc;
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fctx.fillText("\u2113 = " + sol_len.toFixed(1).toString() + "mm", start_x + loop_turns_slider.value*cond_spacing + 20, dim_y + 20);
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}
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drawDesign();
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< / script >
< / body >
< / html >