SpHEAR/TinySphEAR.scad

//
// TinySpHEAR, Tiny Spherical Harmonics Ear, 
// First Order (B-format) Ambisonics Microphone
//
// Copyright 2015-2016, Fernando Lopez-Lezcano, All Rights Reserved
// nando@ccrma.stanford.edu
//
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
//
// 3d Models released under the Creative Commons license as follows:
//   Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
// http://creativecommons.org/licenses/by-nc-sa/4.0/


// https://en.wikipedia.org/wiki/Tetrahedron
// angle of capsule to vertical axis = atan(sqrt(2)) = 54.7356103172

////
//// model parameters

// dimensions of the electret microphone capsule
capsule_radius = 5;
capsule_height = 4.5;

// distance between the face of a capsule and the center of array
//
// for a 10mm capsule: with vertical legs -> 10.5mm min radius
//                     with horizontal legs -> 10mm min radius
mic_radius = 9.6;

// dimensions of the capsule holder connection legs
// a width of 4mm is too thin, 5mm prints better
leg_width = 5;
leg_thick = 3;

// wall thickness of the capsule holder
wall = 1;

// width of the ridge that connects to the mount
//   measured: ridge = 2.20mm, slot = 2.0 .. 2.35mm
ridge_width = 2.0;
ridge_slot_width = 2.0;
// add to the thickness of ridges
ridge_fit = 0.1;

// dimensions of microphone mount
mount_radius = 2.75;
mount_wall = 0.75;

// height of mount
mount_height = 40;

// microphone stand mount
//
// diameter of existing shielded wires (x 4)
mic_wire_diam = 1.5;
mic_wire_hole_radius = 2.5;
mic_wire_hole_offset = 5;

// standard microphone stand
// measured diameter = 13.5, inside diameter of sleeve = 13.79 (
mic_mount_radius = 13.50 / 2;
// add this to inside diameter
mic_mount_fit = 0.1;
mic_mount_slot_height = 11.5;
mic_mount_slot_width = 4.25;
mic_mount_slot_radius = 6.25  / 2;
mic_mount_wall = 1.5;
mic_mount_height = 35.0 + mic_wire_hole_offset + mic_wire_hole_radius + 2 * mic_mount_wall;

//// end of model parameters
////
//// rendering control

// what to render:
// 0 -> ready to print
//   set = 0 -> one capsule, set = 1 -> four capsules
// 1 -> the whole microhone with four capsules
rendermic = 1;
renderset = 0;

// what type of connection to use between capsule holders:
// 0 -> original cylindrical angled legs
// 1 -> interlocking horizontal legs
// 2 -> interlocking vertical legs
connect = 1;

// how many mount ridges to create
// 0 -> no ridges
// 1 -> 1 ridge
// 2 -> 2 ridges
ridges = 1;

//// end of rendering control
////

// elevation angle for the capsule holders (fixed for this microphone)
elev_angle = atan(sqrt(1/2));

// angles of the connection legs and adjacent capsule holders
leg_angles_top = 
    [
        [-120, elev_angle], 
        [0, elev_angle],
        [120, elev_angle]
    ];

leg_angles_bot = 
    [
        [-120, elev_angle], 
        [120, elev_angle]
    ];

// adjustment for the inner radius of the capsule holder
//   measured inside diameter of a trial print was around 7.5 to 8.2 
//   instead of 10, capsule diameter was 9.99)
fudge = 0.15;

// adjustment for fit of slots in connection legs and mount
fit = 0.1;

// number of facets for rendering cylinders
facets = 64;

// microphone structure geometry
capsule_sep_min = (mic_radius - capsule_height) * cos(elev_angle) - (capsule_radius + wall) * sin(elev_angle);
capsule_sep_max = mic_radius * cos(elev_angle) - (capsule_radius + wall) * sin(elev_angle);
capsule_bottom = mic_radius * sin(elev_angle) + (capsule_radius + wall) * cos(elev_angle);
mount_radius_capsule = capsule_sep_max;

////////
// microphone capsule holder

// azimuth: horizontal orientation of the capsule
// elevation: vertical orientation of the capsule
// mounts: vectors containing the angle of the mount and the angle to the adjacent capsule
// twist: rotate the whole capsule to match mounting legs
// ridge: add 0, 1 or 2 ridges for attaching the structure to the mount
// ridge_fit: tune the fit, used for carving slots in mount
// solid: make the capsule holder solid, used in the mount code to carve the capsule rests

module capsule (azimuth, elevation, mounts, twist, ridge, ridge_fit = 0.0, solid = 0) {
    rotate([0, 0, azimuth]) {
        rotate([0, (90 - elevation), 0]) {
            translate([0, 0, (rendermic == 0 && solid == 0) ? 0 : mic_radius - capsule_height]) {
                difference () {
                    union () {
                        // main capsule holder
                        cylinder(r = capsule_radius + wall, h = capsule_height, $fn = facets);    
                        // the mounting legs
                        for (angles = mounts) {
                            rotate([0, 0, angles[0] + twist]) {
                                // connect with cylindrical beams, very pretty
                                if (connect == 0) {
                                    leg_length = mic_radius * cos(angles[1]) - capsule_radius * sin(angles[1]);
                                    translate([capsule_radius - wall, 0, capsule_height - wall]) {
                                        rotate([0, 180 - angles[1], 0]) {
                                            cylinder(d = leg_width, h = leg_length - 0.3, center = false, $fn = facets);
                                        }
                                    }
                                }
                                // connect with horizontal legs
                                if (connect == 1) {
                                    leg_length = (mic_radius - capsule_height + leg_thick) * tan(90 - angles[1]) - capsule_radius;
                                    slot_depth = leg_thick * cos(90 - 2 * angles[1]) + wall + fit;
                                    translate([capsule_radius + leg_length + fudge, - leg_width / 3, 0]) {
                                        rotate([0, -90, 0]) {
                                            difference() {
                                                // thickness, width
                                                cube([leg_thick, leg_width, leg_length]);
                                                // cut slot in connector
                                                translate([0, leg_width / 3 - (fit / 2), 0]) {
                                                    cube([leg_thick, leg_width / 3 + fit, slot_depth]);
                                                }
                                            }
                                        }
                                    }
                                }
                                // connect with vertical legs
                                if (connect == 2) {
                                    // fix this 0.2 == (2 * fudge?)
                                    leg_length = (mic_radius * tan(90 - angles[1]) - capsule_radius) * tan(angles[1]) - 0.2; 
                                    slot_depth = leg_thick * cos (90 - (2 * angles[1]));
                                    translate([capsule_radius - leg_thick / 2 + fudge, - leg_width / 3, 
                                               - leg_length + capsule_height]) {
                                        difference() {
                                            // the connection
                                            difference() {
                                                cube([leg_thick + leg_thick / 2, leg_width, leg_length]);
                                                translate([-leg_thick + wall - fudge, 0, - capsule_height + fudge]) {
                                                    cube([leg_thick, leg_width, leg_length]);
                                                }
                                            }
                                            // cut slot in connector
                                            translate([0, leg_width / 3 - (fit / 2), 0]) {
                                                cube([leg_thick + leg_thick / 2, leg_width / 3 + fit, slot_depth]);
                                            }
                                        }
                                    }
                                }
                            }
                        }
                        // add ridges for microphone mount
                        ridge_length = (mic_radius - capsule_height) / tan(elev_angle) - (capsule_radius + wall);
                        if (ridge == 2) {
                            rotate([0, 0, twist]) {
                                translate([capsule_radius + wall - ridge_length / 2, (ridge_width - ridge_fit) / 2, 0]) {
                                    cube([ridge_length * 3 / 2, ridge_width - ridge_fit, capsule_height], center = false);
                                }
                                translate([capsule_radius + wall - ridge_length / 2, - (ridge_width - ridge_fit) * 3 / 2, 0]) {
                                    cube([ridge_length * 3 / 2, ridge_width - ridge_fit, capsule_height], center = false);
                                }
                            }
                        }
                        if (ridge == 1) {
                            rotate([0, 0, twist]) {
                                translate([capsule_radius + wall - ridge_length / 2, - (ridge_width - ridge_fit) / 2, 0]) {
                                    cube([ridge_length * 3 / 2, ridge_width - ridge_fit, capsule_height], center = false);
                                }
                            }
                        }
                    }
                    // make the hole for the capsule (also cuts leg overhang for vertical connectors)
                    if (solid != 1) {
                        translate ([0, 0, -capsule_height]) {
                            cylinder(r = capsule_radius + fudge, h = capsule_height * 2, $fn = facets);
                        }
                    }
                    // remove any extra connecting beam material from the face of the holder
                    if (connect == 0) {
                        translate ([0, 0, capsule_height]) {
                            cylinder(r = capsule_radius + wall * 2, h = 2, $fn = facets);
                        }
                    }
                }
            }
        }
    }
}

// microphone mount
//
// clips into standard microphone stand
//
// angles: angles for mount slots
// wall: thickness of cylinder wall
// stand_wall: thickness of stand mount wall
// separation: height of mount with respect of the microphone assembly

module ellipsoid(height, rad_bot, rad_top, eccentricity) {
    linear_extrude(height = height, scale = [eccentricity, rad_top / rad_bot]) {
        circle(r = rad_bot, $fn = facets); 
    }
}

module mount (angles, wall, stand_wall, separation) {
    cone_height = 5;
    translate([0, 0, -separation]) {
        difference() {
            union() {
                // conic section
                translate([0, 0, mic_mount_height + mount_height]) {
                    rotate([0, 0, 45]) {
                        difference() {
                            ellipsoid(cone_height, mount_radius + wall, mount_radius_capsule, 1.4);
                            ellipsoid(cone_height, mount_radius, mount_radius_capsule * 0.5, 1.4 * 1.1);
                        }
                    }
                }
                // stalk
                translate([0, 0, mic_mount_height + mount_height * 2/3]) {
                    difference() {
                        cylinder(r = mount_radius + wall, h = mount_height / 3, $fn = facets);
                        // make the hole for the mount
                        cylinder(r = mount_radius, h = mount_height / 3, $fn = facets);
                    }
                }
                // transition to stand mount
                translate([0, 0, mic_mount_height]) {
                    difference() {
                        cylinder(r2 = mount_radius + wall, r1 = mic_mount_radius + mic_mount_fit + stand_wall, 
                                h = mount_height * 2 / 3, $fn = facets);
                        // make the hole for the mount
                        cylinder(r2 = mount_radius, r1 = mic_mount_radius + mic_mount_fit, 
                                h = mount_height * 2 / 3, $fn = facets);
                    }
                }
                // stand mount
                translate([0, 0, 0]) {
                    difference() {
                        union() {
                            // main mount cylinder
                            translate([0, 0, 0]) {
                                difference() {
                                    cylinder(r = mic_mount_radius + mic_mount_fit + stand_wall, h = mic_mount_height, $fn = facets);
                                    // make the hole for the mount (* 1.5 to cut the ridge as well)
                                    cylinder(r = mic_mount_radius + mic_mount_fit, h = mic_mount_height, $fn = facets);
                                }
                            }
                        }
                        // slot for fitting into microphone stand
                        translate([mic_mount_radius - stand_wall / 2, - mic_mount_slot_width / 2, 0]) {
                            cube([2 * stand_wall, mic_mount_slot_width, mic_mount_slot_height]);
                        }
                        // eyelet for microphone stand
                        translate([mic_mount_radius - stand_wall / 2, 0,  mic_mount_slot_height]) {
                            rotate([0, 90, 0]) {
                                cylinder(r = mic_mount_slot_radius, h = 2 * stand_wall, $fn = facets);
                            }
                        }
                        // hole for microphone wiring
                        translate([mic_mount_radius - stand_wall / 2, 0, mic_mount_height - mic_wire_hole_offset]) {
                            rotate([0, 90, 0]) {
                                cylinder(r = mic_wire_hole_radius, h = 2 * stand_wall, $fn = facets);
                            }
                        } 
                    }
                }
            }
            // indentations that match the two lower capsule holders
            translate([0, 0, mic_mount_height + mount_height + cone_height + 
                       (mic_radius - capsule_height) + capsule_height * sin(elev_angle)]) {
                capsule(angles[0], -elev_angle, [], 0, 1, 0.1, 1);
                capsule(angles[1], -elev_angle, [], 0, 1, 0.1, 1);
            }
        }
    }
}

// render a complete microphone

if (rendermic == 1) {
    // all four capsules
    capsule(45, elev_angle, leg_angles_top, 60, 0, 0.0, 0);
    capsule(-135, elev_angle, leg_angles_top, 60, 0, 0.0, 0);
    capsule(-45, -elev_angle, leg_angles_bot, 0, 1, 0.0, 0);
    capsule(135, -elev_angle, leg_angles_bot, 0, 1, 0.0, 0);
    // the mount
    mount([-45, 135], mount_wall, mic_mount_wall, mic_mount_height + mount_height + 5 + capsule_bottom);
}

// print all the parts separately

if (rendermic == 0) {
    if (connect == 1) {
        part_rot = 90;
        part_height = 0;
        part_sep = capsule_radius * 2.5;
        // #3
        translate([part_sep, -part_sep, part_height]) { capsule(0, part_rot, leg_angles_top, 60, 0); }
        if (renderset != 0) {
            // #4
            translate([part_sep, part_sep, part_height]) { capsule(0, part_rot, leg_angles_top, 60, 0); }
            // #2
            translate([-part_sep, part_sep, part_height]) { capsule(0, part_rot, leg_angles_bot, -90, 1); }
            // #1
            translate([-part_sep, -part_sep, part_height]) { capsule(0, part_rot, leg_angles_bot, 90, 1); }
            // mount body
            translate([0, 0, mount_height]) { mount([-45, 135], 1, 0); }
            // add connecting ridges to make it all one part
            difference() {
                for (rot_a = [-45, 45]) {
                    rotate([0, 0, rot_a]) {
                        translate([-wall / 2, -part_sep, 0]) {
                            cube([wall, part_sep * 2, wall / 2]);
                        }
                    }
                }
                // remove them in the inside of the mount
                cylinder(r = mount_radius + wall / 2, h = wall / 2);
            }
        }
    } else {
        // connect == 2
        part_rot = -90;
        part_height = capsule_height;
        part_sep = capsule_radius * 2;
        // #3
        translate([part_sep, -part_sep, part_height]) { capsule(0, part_rot, leg_angles_top, 0, 0); }
        if (renderset != 0) {
            // #4
            translate([part_sep, part_sep, part_height]) { capsule(0, part_rot, leg_angles_top, 0, 0); }
            // #2
            translate([-part_sep, part_sep, part_height]) { capsule(0, part_rot, leg_angles_bot, -90, 1); }
            // #1
            translate([-part_sep, -part_sep, part_height]) { capsule(0, part_rot, leg_angles_bot, 90, 1); }
            // stand mount
            *translate([0, 0, 0]) {
                mount_to_stand([-45, 135], mount_wall, mic_mount_wall, 0);
            }
            // add connecting ridges to make it all one part
            difference() {
                for (rot_a = [-45, 45]) {
                    rotate([0, 0, rot_a]) {
                        translate([-wall / 2, -part_sep * 0.85, 0]) {
                            cube([wall, part_sep * 1.75, wall / 2]);
                        }
                    }
                }
                // remove them in the inside of the mount
                *cylinder(r = mic_mount_radius + mount_wall / 2, h = wall / 2);
            }
        }
    }
}