SpHEAR/first_order.scad

//
// First Order (B-format) Ambisonics Microphone, or Bambi for short
//
// Copyright 2015 Fernando Lopez-Lezcano
//
// Code released under the GNU GPL License
// http://www.gnu.org/licenses/gpl-3.0.en.html
//
// 3d models under Creative Commons Non-Commercial Share-alike, CC-NC-SA 3.0
// http://creativecommons.org/licenses/by-nc-sa/3.0/


// microphone capsule holder

module capsule (azimuth, elevation, separation, radius, height, wall, twist) {
	rotate([0, 0, azimuth]) {
	rotate([0, (90 - elevation), 0]) {
  translate([0, 0, separation]) {
		// the capsule holder
		difference () {
				union () {
					// main capsule holder
					cylinder(r = radius + wall, h = height, $fn = 128);	
					// ridge to stop capsule when inserted
					translate(v = [0, 0, - (wall / 2)]) {
						difference() {
							cylinder(r = radius + wall, h = wall / 2, $fn = 128);
							cylinder(r = radius - 0.4, h = wall / 2, $fn = 128);
						}
					}
					// the attachment point to the other capsules
					for (rot = [0 : 120 : 360]) {
						rotate(a = rot + twist, v = [0, 0, 1]) {
							translate(v = [radius + wall, 0, wall * 2]) {
								rotate(a = 145, v = [0, 1, 0]) {
									cube([wall * 2.5, wall * 2, separation], center=true);
//								  cylinder(d=wall * 3, h = seaparation, center=true);
								}
							}
						}
					}
				}
				// the inside of the capsule holder
				cylinder(r=radius, h=height, $fn = 128);
				// remove the upper part of the attachment points
				translate(v = [0, 0, height]) {
					cylinder(r = radius + wall, h = wall);
				}
			};
		}
	}
}
}

// vectors pointing in the directions of the four capsules
direction1 = [1, 1, 1];
direction2 = [-1, 1, -1];
direction3 = [-1, -1, 1];
direction4 = [1, -1, -1];

dist = sqrt(3);

// azimuths
az1 = atan2(1, 1);
az2 = atan2(1, -1);
az3 = atan2(-1, -1);
az4 = atan2(-1, 1);

// elevations
el1 = asin(1/dist);
el2 = -asin(1/dist);
el3 = asin(1/dist);
el4 = -asin(1/dist);

// dimensions for the EM182 electret microphone

mic_radius = 5;
mic_height = 4.5;

// seaparation between capsules
cap_sep = 6;

// connect the four instances together
capsule(az1, el1, cap_sep, mic_radius, mic_height, 1, 60);
capsule(az2, el2, cap_sep, mic_radius, mic_height, 1, 0);
capsule(az3, el3, cap_sep, mic_radius, mic_height, 1, 60);
capsule(az4, el4, cap_sep, mic_radius, mic_height, 1, 0);

// just one to test
//capsule(0, -90, cap_sep, mic_radius, mic_height, 1, 0);