Toilet key hacking


The toilet keys on the camping site consist of a plastic carrier holding a 4x3 matrix of magnets. Each magnet encodes one bit, but the pattern looks like an L-shape.

    0 = S
    1 = N
    
    1 0 0
    1 0 0
    1 0 0
    1 1 1

Someone did a draft for a 3d printed version in openscad; the magnet size is 5mm in diameter and 2mm in height.

NOTE: This is only a draft and may still need some adaption, as we didn't have enough magnets to test
    y_magnet_pos = [31,40,49,58];
    x_magnet_pos = [5,14,23];
    magnet_spacing = 9;
    magnet_dia = 5;
    magnet_h = 2;
    
    module magnet()
    {
        color([.6,.6,.6]) cylinder(d=5, h=2, $fn=30, center=true);
    }
    module camping_toilet_key()
    {
        difference() {
            cube([28,64,4]);
            translate([23,5,-.1]) cylinder(d=5, h=4.2, $fn=30);
            for(y = y_magnet_pos) {
                for(x = x_magnet_pos) {
                    translate([x, y, .8])
                    cylinder(d=magnet_dia+.4, h=magnet_h+.4, $fn=60);
                    for(xd = [-2,0,2])
                    translate([x + xd, y, 4.2]) cube([1,magnet_dia + 1,2], center=true);
                }
                translate([28/2 + 5, y, 2])
                    cube([28,magnet_dia + .1,magnet_h+.4], center = true);
                translate([28/2 - 5, y, 2])
                    cube([28, magnet_dia/2, magnet_h+.4], center = true);
                translate([28/2, y - magnet_spacing/2, 2])
                    cube([26, (magnet_spacing - magnet_dia - 1), magnet_h+.4], center = true);
            }
        }
    }
    camping_toilet_key();