change to 10x1206 resistors

README.md

@@ -1,18 +1,51 @@
-# ScopeShunt33
+# ScopeShuntX
 
-![](pcb/ScopeShunt33.jpg)
+![](pcb/ScopeShuntX.jpg)
 
-![](enclosure/ScopeShunt33_enclosure.png)
+![](enclosure/ScopeShuntX_enclosure.png)
 
-BOM https://www.digikey.com/short/n542tnnq
+BOM https://www.digikey.com/short/3z3bj7z3
 
 PCB https://www.pcbway.com/project/shareproject/ScopeShunt33_095d5357.html
 
 PCB Gerbers & Enclusure STLs in [RELEASES](../../releases/)
 
-Be careful soldering the BNC connector. The solid metal body sinks the heat away from the two main legs and makes it difficult to get the legs hot enough to solder, and then by the time you do get them hot enough, the body has heated up to the point where the insulation is melting inside.
-
-For the two main legs, use a large tip with the heat turned up over 400C, and heat the tips of the legs on the bottom side of the pcb as fast as possible, solder, and get out of there and stop adding heat as fast as possible before the rest of the connector heats up and the insulation melts. Don't try to get the solder to flow all the way to the top side of the pcb.
+# Resistor Values -> Current Ranges -> Scope Readings
+The BOM above includes 10 mOhm resistors, which makes a shunt suitable for measuring 1A to 100A (Really only about 20A, see (2) below), which is mostly suitable for automotive work.
+
+To measure other current ranges, substitute one of these other resistors instead.  
+Remember in all cases to use:  
+ * qty 10 resistors (a few spares is recommended also, but the PCB needs 10)  
+ * 1206 size (normal, not "wide" orientation)  
+ * 1% tolerance or less  
+ * Recommend to use the highest power rating you can get, to make it less likely to destroy when accidentally connected to too-high current  
+
+<!-- general search, all resistances https://www.digikey.com/short/wwhwwcjd -->
+
+ | Individual<br>Resistors | Total<br>Resistance | Current<br>Range | Scope<br>Reading | Catasrophic<br>Failure |
+ | --- | --- | --- | --- | --- |
+ | [10 kOhm 1 W](https://www.digikey.com/short/cfbp8cz7) | 1 kOhm | 100 uA | 1 mV = 1 uA | 100mA 100V |
+ | [1 kOhm 3/4 W](https://www.digikey.com/short/vp9hpb5z) | 100 Ohm | 1 mA | 1 mV = 10 uA | 270mA 27V (1) |
+ | [100 Ohm 1 W](https://www.digikey.com/short/dbw91twt) | 10 Ohm | 10 mA | 1 mV = 100 uA | 1A 10V |
+ | [10 Ohm 1 W](https://www.digikey.com/short/b54bzdjr) | 1 Ohm | 100 mA | 1 mV = 1 mA | 3A 3V |
+ | [1 Ohm 3/4 W](https://www.digikey.com/short/f9hpctpn) | 100 mOhm | 1 A | 1 mV = 10 mA | 8.6A 860mV (1) |
+ | [100 mOhm 1 W](https://www.digikey.com/short/brpqvpnv) | 10 mOhm | 10 A | 1 mV = 100 mA | 30A 300mV (2) |
+ | [10 mOhm 1 W](https://www.digikey.com/short/mjnfq7dt) | 1 mOhm | 100 A | 1 mV = 1 A | 100A 100mV (2) |
+
+ (1) Reflects the listed 3/4W resistors because 1W not available. Would be a little higher with 1W parts.
+
+ (2) The practical current limit is much lower for a few reasons. In decreasing order:
+
+ * This design uses size 1206 resistors, which aren't available in power ratings over 1W. 100A would be 100% of the resistors rated capacity, which they can't actually sustain for long. If the resitors were the only consideration, then the practical limit would be more like 75A for continuous use, 100A for brief periods  
+ * The PCB uses zone fills rather than traces for all connections, so it's difficult to calculate the max current the PCB traces can carry. Here is a table based on 4mm wide traces x 2 traces per pin. The PCB has significantly more copper than this, and can probably handle significantly more than these values.  
+ | CU Oz | Amps<br>+10°C | Amps<br>+45°C |
+ | --- | --- | --- |
+ | 1 | 6.4 | 13 |
+ | 2 | 10  | 20 |
+ | 3 | 13.5 | 27.5 |
+ TL,DR: If you're going to be routinely measuring over 10A, be sure to oder the PCB with 2oz copper or more.
+
+ * The terminal block is only rated for 16A
 
 # History / Credits
 Inspired by https://github.com/voltlog/ScopeShunt

ScopeShuntX.bom.csv

@@ -0,0 +1,5 @@
+"Index","Quantity","Part Number","Manufacturer Part Number","Description","Customer Reference","Available","Backorder","Unit Price","Extended Price USD"
+"1","1","732-10955-ND","691137710002","TERM BLK 2POS SIDE ENTRY 5MM PCB","","1","0","0.39000","0.39"
+"2","1","J6536-ND","415-0057-036","CBL ASSY BNC PLUG-PLUG RG59 36""","","1","0","12.49000","12.49"
+"3","1","A32274-ND","5414373-1","CONN BNC JACK R/A 50 OHM PCB","","1","0","3.23000","3.23"
+"4","10","CFN1206-FX-R010ELFCT-ND","CFN1206-FX-R010ELF","RES 0.01 OHM 1% 1W 1206","","10","0","0.43600","4.36"

enclosure/ScopeShunt33_enclosure.scad → enclosure/ScopeShuntX_enclosure.scad

@@ -1,4 +1,4 @@
-// Enclosure for ScopeShunt33
+// Enclosure for ScopeShuntX
 
 // OUTPUT
 /***********************************************************/
@@ -12,20 +12,20 @@ display_assembly();
 // To generate this STL model of the PCB:
 // KiCad -> pcbnew -> File -> Export -> Step -> ScopeShunt33_pcb.step
 // FreeCAD -> File -> open *.step -> select body -> File -> Export -> STL -> ScopeShunt33_pcb.stl
-pcb_model_stl = "../pcb/ScopeShunt33_pcb.stl";
+pcb_model_stl = "../pcb/ScopeShuntX_pcb.stl";
 
 corner_radius = 2.5;
 wall_thickness = 1;
 pcb_thickness = 1.6;
-pcb_length = 35;
-pcb_width = 40;
-pcb_x_offset = -5.5;  // pcb model stl center
-pcb_y_offset = 0;     // "   "     "   "
+pcb_length = 18.5;
+pcb_width = 28;
+pcb_x_offset = 0;  // pcb model stl center
+pcb_y_offset = 0;  // "   "     "   "
 top_components_thickness = 0.8; // resistors 0.65
 bottom_components_thickness = 2;
-top_perimeter_lip = 0.8;
+top_perimeter_lip = 1;
 bottom_perimeter_lip = 1;
-fitment_clearance = 0.1;
+fitment_clearance = 0.2;
 snap_length = 6;
 snap_thickness = wall_thickness;
 snap_clearance = 0.3;
@@ -109,6 +109,7 @@ module shell_top() {
    // holes
    bnc_hole();
    terminal_hole();
+
   } // diff cut
  } // difference
 
@@ -157,7 +158,7 @@ module shell_bottom() {
    sx = 1+sl+1;
    sy = o+st/2+sc;
    sz = st+sc+o;
-   translate([0,0,sz/2-bcz-fc-wt-o]){
+   translate([0,0,sz/2-bcz-fc-wt-o]) {
     mirror_copy([0,1,0])
      translate([0,-py/2-fc/2-o+sy/2,0])
       cube([sx,sy,sz],center=true);
@@ -171,31 +172,43 @@ module shell_bottom() {
 } // shell_bottom()
 
 module terminal_hole() {
- translate([11.5,14,tcoz/2+pz])
-  hull()
-   mirror_copy([0,1,0])
-    translate([0,5,0])
-     mirror_copy([1,0,0]) 
-      translate([5,0,0])
-       cylinder(h=tcoz,r=0.4,center=true);
-  // clearance for the dovetails
-  translate([16.3,14.5,tcoz/2+pz])
-   mirror_copy([0,1,0])
-    translate([0,3.55,0])
-     cylinder(h=tcoz,r=1.2,center=true);
+ x = 11.1; // opening x
+ y = 11.4; // opening y
+ xpos = 2.5; // x position
+ ypos = 6; // y position
+ zpos = tcoz/2+pz; // z position
+ cr = 0.5; // corner radius
+ dcr = 1; // dovetail clearance radius
+ dtx = 0.65; // dovetail hight from side wall
+ translate([xpos,ypos,zpos]) {
+   hull()
+    mirror_copy([0,1,0])
+     translate([0,y/2-cr,0])
+      mirror_copy([1,0,0]) 
+       translate([x/2-cr,0,0])
+        cylinder(h=tcoz,r=cr,center=true);
+   // clearance for the dovetails
+   translate([x/2-dcr+dtx,0,0])
+    mirror_copy([0,1,0])
+     translate([0,3.55,0])
+      hull()
+       mirror_copy([0,1,0])
+        translate([0,dcr,0])
+         cylinder(h=tcoz,r=dcr,center=true);
+  }
 }
 
 module bnc_hole () {
  vw = bnc_diameter + bnc_clearance; // vertical width
  hw = fc + bnc_diameter + fc; // horizontal width
- bxo = 11.5; // bnc x offset
+ bxo = 2.5; // bnc x offset
  cr = 0.4; //corner radius
  // hole in wall
  translate([bxo,-(o+wt+fc+tpl+o)/2-py/2+tpl+o,5.45])
   rotate([90,0,0])
    cylinder(h=o+wt+fc+tpl+o,d=vw,center=true);
  // hole in top
- translate([bxo,-13,tcoz/2+pz])
+ translate([bxo,-7,tcoz/2+pz])
   hull(){
    cylinder(h=tcoz,d=hw,center=true);
    translate([0,cr-7.1,0])