Float switch

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Revision as of 22:10, 9 May 2017 by James (talk | contribs) (v5 update to adjust foot threads, etc.)
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This is the source code for the float switch 3d printed parts for the water level detector for the Cheap Chinese Laser. It is made in two parts: the head and the base. You also need 4 pieces of 1/4-20 all thread to connect the two of them and 8 nuts. The base is internally threaded. The head needs nuts top and bottom. Washers would be good too.

File:Float-switch-head.stl rendered on 5/1/2017

File:Float-switch-base.stl rendered on 5/7/2017

low water level detector
safety interlock for cheap Chinese laser at Hac DC
This water level detector is a two piece assembly connected by threaded rod.  This model uses 1/4-20 rod.  The lower foot has a 40mm home in the bottom to insert a pingpong ball as the float.
James Sullivan
Mk 5 - removed tolerance variable and adjusted threads, ppbd, and head threaded rod holes diameters
OpenSCAD version 2015.03-1 
ppbd=41;    //ping pong ball diameter, includes 1mm tolerance
ppbw=2.7;   //ping pong ball weight in grams
shd=2;  //switch hole diameter
shp=10; //switch hole pitch, i.e. center to center spacing of mounting holes on microswitch
wlh=200;    //water level height
sbw=6;  //switch body width
nfw=4;  //nut face width, switch mounting nuts
nt=1;   //nut thickness, switch mounting nuts
thick=5;    //thickness
eps=0.1;    //epsilon
br=50;      //base radius
rod=25.4/4; //rod outer diameter
tpi=20;     //threads per inch
td=13.74/tpi;   //thread depth
fph=25.4*5/tpi;//foot pillar height
bfw=ppbd+2*thick;  //base flange width
function mod(num,den) = num - floor(num/den)*den; 
//dimensions taken from Front Door Switch Holder
wr=4;			//wrench size for nuts width across flats
nh=1;			//nut height, depth of nut sockets

module head() {
    color("cyan") difference(){
                rotate([0,0,angle]) translate([ppbd/2+rod/2+td,0,0]) cylinder(d=rod+thick*2,h=thick); //leg cylinders
        translate([0,0,-thick/2]) cylinder(h=thick*2,r=ppbd/2+rod/2-3*thick/2);  //center bore to reduce material amount and print time
            rotate([0,0,angle]) translate([ppbd/2+rod/2+td,0,-thick/2]) cylinder(d=rod*1.1,h=thick*2); //leg holes for threaded rods
    translate([sbw/2,(ppbd+rod-2*thick)/(-2),0]) cube([thick,ppbd+rod-2*thick,thick]);  //support for switch mounting block
    translate([sbw/2,shp/2,thick]) difference(){ //switch mounting block, aligned with z-plane and x-plane, centered on y-plane
        translate([0,-shp/2-nfw,0]) color("green") cube([thick,shp+2*nfw,2*nfw]);
        for (y=[-shp/2,shp/2]) {
            translate([thick/2,y,nfw]) rotate([0,90,0]) cylinder(d=shd,h=thick*2,center=true);    //screw holes
            translate([sbw-nh,y,nfw]) union(){  //nut sockets
                for (ang=[0,120,240]) rotate([ang,0,0]) cube([nh*2,wr,wr/sqrt(3)],center=true);
        translate([sbw/2+thick,bfw/2-nfw-shp,nfw]) union(){  //center nut socket
            rotate([120,0,0]) cube([nh*2,wr,wr/sqrt(3)],center=true);
            rotate([240,0,0]) cube([nh*2,wr,wr/sqrt(3)],center=true);

module socket(nd,tpi,tl,thick) {
    //nd = nominal diameter
    //tpi = threads per inch
    //tl = thread length
    ror=nd/2;       //rod outer radius
    pitch=25.4/tpi; //thread pitch in mm
    td=13.74/tpi;   //thread depth in mm
    rir=ror-td;     //rod inner radius
    sor=ror+thick;  //socket outer radius
    vert= [for (ang=[0:360/$fn:720]) ang<=90 ? [cos(ang),sin(ang)]*rir : 
        ang<202.5 ? [cos(ang),sin(ang)]*(rir+td*(ang-90)/112.5) : 
        ang<=247.5 ? [cos(ang),sin(ang)]*ror : 
        ang<360 ?[cos(ang),sin(ang)]*(rir+td*(360-ang)/112.5) : 
    path1=[for(p=[0:$fn]) p<$fn ? p : 0 ];
    path2=[for(p=[$fn:2*$fn]) p<2*$fn ? p : $fn ];
    color("green") difference(){
        translate([0,0,tl-ror*tan(30)]) cylinder(r2=ror,r1=0,h=ror*tan(30));  //inlet chamfer

module foot(){
            translate([0,0,thick/2]) cube([ppbd+2*thick,ppbd+2*thick,thick],center=true);
            for (angle=[45:90:315]){
                    translate([ppbd/2+rod/2+13.74/tpi,0,thick]) socket(rod*1.1,tpi,fph,thick);  //pillar
                    translate([0,-thick,0]) cube([br-thick,thick*2,thick]); //leg
                    translate([br-thick,0,0]) cylinder(r=thick,h=thick);    //foot
                }  //end rotate
            }  //end for
        }  //end union
        translate([0,0,-eps/2]) cylinder(d=ppbd,h=fph+eps+thick); //ping pong ball entry
    }   //end difference
}   //end foot module