Add PT_camera to examples and gallery

examples/PT_camera/PT_camera.scad

@@ -0,0 +1,54 @@
+include <../../vitamins/geared_steppers.scad>
+include <../../core.scad>
+include <../../vitamins/cameras.scad>
+use <../../vitamins/pcb.scad>
+
+module ptc(ang2) {
+  rotate([180,0,0])
+    union(){
+      geared_stepper(28BYJ_48,ang2);
+      rotate([90,0,180-ang2])
+        translate([9.8,-16.5,1.7])
+          rotate([0,0,90])
+            camera(cameras[0]);
+    }
+}
+
+module pt(ang,ang2) {
+  rotate([180,0,0]) geared_stepper(28BYJ_48,ang);
+  rotate([0,0,ang]) rotate([270,0,0]) translate([0,-29.0,-1.5]) ptc(ang2);
+}
+
+deg=90;
+c=90;
+
+if($t<0.125){
+  a=180+$t/0.125*deg;
+  pt(a,c);
+}else if ($t<0.25){
+  a=180+deg-($t-0.125)/0.125*deg;
+  pt(a,c);
+}else if ($t<0.375){
+  b=c+($t-0.25)/0.125*deg;
+  pt(180,b);
+}else if ($t<0.5){
+  b=c+deg-($t-0.375)/0.125*deg;
+  pt(180,b);
+}   
+else if($t<0.625){
+  a=180+($t-0.5)/0.125*deg;
+  b=c+deg-90+($t-0.5)/0.125*deg;
+  pt(a,b);
+}else if ($t<0.75){
+  a=180+deg-($t-0.625)/0.125*deg;
+  b=c+deg-($t-0.625)/0.125*deg;
+  pt(a,b);
+}else if ($t<0.875){
+  a=180-($t-0.75)/0.125*deg;
+  b=c-($t-0.75)/0.125*deg;
+  pt(a,b);
+}else{
+  a=90+($t-0.875)/0.125*deg;
+  b=c+deg-180+($t-0.875)/0.125*deg;
+  pt(a,b);
+}   

gallery/readme.md

@@ -106,6 +106,10 @@ A base and shroud to make PSU safe to sit on a desk
 
 ![](PSU_tube.png)
 
+## PT_camera
+Two 28BYJ_48 geared stepper motors and a Raspberry v1 camera, combined with [4 drops of superglue](https://forums.raspberrypi.com/viewtopic.php?p=1810000#p1810000). Script [PT_camera.scad](../examples/PT_camera/PT_camera.scad) nicely demonstrates new 2nd optional arg (motor shaft angle) of ```geared_stepper()```.  
+![](PT_camera.anim.gif)
+
 ## PotBox
 Potentiometer box with course and fine controls and three 4mm binding posts