The New Hotness

The folks I’ve been coaching through their plotter build project showed it off at the local MiniMakerFaire this past weekend. Next time around, I’ll insist they secure their circuit boards and use good wiring techniques, so as to avoid destroying more stepper drivers.

To that end, adding mounting holes to my proto board holder seems in order:

Proto Board Holder 90x70 - Flange mounting holes - Slic3r preview — Proto Board Holder 90×70 – Flange mounting holes – Slic3r preview

The board dimensions now live in an associative array, so you just pick the board name from a Configurator drop-down list:

/* [Options] */

PCBSelect = "ArdUno"; // ["20x80","40x60","30x70","50x70","70x90","80x120","ArdDuemil","ArdMega","ArdPro","ArdUno","ProtoneerCNC"]

PCB_NAME = 0;
PCB_DIMENSION = 1;

PCBSizes = [
  ["40x60",[40,60,1.6]],
  ["30x70",[30,70,1.6]],
  ["50x70",[50,70,1.6]],
  ["20x80",[20,80,1.6]],
  ["70x90",[70,90,1.6]],
  ["80x120",[80,120,1.6]],
  ["ArdDuemil",[69,84,1.6]],
  ["ArdMega",[102,53.5,1.6]],
  ["ArdPro",[53,53.5,1.6]],
  ["ArdUno",[69,53.1,1.6]],
  ["ProtoneerCNC",[69,53.1,1.6]],
];

Which seems easier than keeping track of the dimensions in comments.

You can now put the PCB clamp screws and mounting holes on specific corners & sides, allowing oddball locations for Arduino boards with corner cutouts along the right edge:

Proto Board Holder ArdUno - Slic3r preview — Proto Board Holder ArdUno – Slic3r preview

A “selector” notation separates the hole location from the board dimensions & coordinates:

ScrewSites = [
//  [-1,1],[1,1],[1,-1],[-1,-1],        // corners
//  [-1,0],[1,0],[0,1],[0,-1]           // middles
  [-1,1],[-1,-1],[1,0]                  // Arduinos
];

Might not be most obvious way, but it works for me. Most of the time, corner clamps seem just fine, so I’m not sure adding the clamp and mounting hole locations to the dimension array makes sense.

The OpenSCAD source code as a GitHub Gist:

	// Test support frame for proto boards
	// Ed Nisley KE4ZNU – Jan 2017
	// June 2017 – Add side-mount bracket, inserts into bottom
	// 2017-11 – Selectable board sizes, chassis mounting holes

	/* [Options] */

	PCBSelect = "ArdUno"; // ["20×80","40×60","30×70","50×70","70×90","80×120","ArdDuemil","ArdMega","ArdPro","ArdUno","ProtoneerCNC"]

	Layout = "Frame"; // [Frame, Bracket]

	ClampFlange = true; // external flange

	Mounts = true; // frame to chassis screw holes

	Channel = false; // wiring channel cutout

	WasherRecess = false; // cutout around screw head

	/* [Extrusion parameters] */

	ThreadThick = 0.25; // [0.15, 0.20, 0.25]
	ThreadWidth = 0.40;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	/* [Hidden] */

	Protrusion = 0.1;

	HoleWindage = 0.2;

	inch = 25.4;

	Tap4_40 = 0.089 * inch;
	Clear4_40 = 0.110 * inch;
	Head4_40 = 0.211 * inch;
	Head4_40Thick = 0.065 * inch;
	Nut4_40Dia = 0.228 * inch;
	Nut4_40Thick = 0.086 * inch;
	Washer4_40OD = 0.270 * inch;
	Washer4_40ID = 0.123 * inch;

	Tap6_32 = 0.106 * inch;
	Clear6_32 = 0.166 * inch;
	Head6_32 = 0.251 * inch;
	Head6_32Thick = 0.097 * inch;
	Nut6_32Dia = 0.312 * inch;
	Nut6_32Thick = 0.109 * inch;
	Washer6_32OD = 0.361 * inch;
	Washer6_32ID = 0.156 * inch;

	ID = 0;
	OD = 1;
	LENGTH = 2;

	//- PCB sizes
	// the list must contain all the selection names as above

	//* [Hidden] */
	PCB_NAME = 0;
	PCB_DIMENSION = 1;

	PCBSizes = [
	["40×60",[40,60,1.6]],
	["30×70",[30,70,1.6]],
	["50×70",[50,70,1.6]],
	["20×80",[20,80,1.6]],
	["70×90",[70,90,1.6]],
	["80×120",[80,120,1.6]],
	["ArdDuemil",[69,84,1.6]],
	["ArdMega",[102,53.5,1.6]],
	["ArdPro",[53,53.5,1.6]],
	["ArdUno",[69,53.1,1.6]],
	["ProtoneerCNC",[69,53.1,1.6]],
	];

	PCBIndex = search([PCBSelect],PCBSizes)[0];
	PCBSize = PCBSizes[PCBIndex][PCB_DIMENSION];

	//echo(str("PCB Size Table: ",PCBSizes));
	//echo(str("PCB Select: ",PCBSelect));
	//echo(str("PCB Index: ",PCBIndex));
	echo(str("PCB Size: ",PCBSize));

	/* [Sizes] */

	WallThick = 4.0; // basic frame structure

	FrameHeight = 10.0;

	/* [Hidden] */

	Insert = [3.9,4.6,5.8];

	PCBShelf = 1.0; // width of support rim under PCB

	Clearance = 1*[ThreadWidth,ThreadWidth,0]; // around PCB on all sides

	ScrewOffset = ThreadWidth + Insert[OD]/2; // beyond PCB edges
	echo(str("Screw offset: ",ScrewOffset));

	/* [Screw Selectors] */

	// ij selectors for PCB clamp screw holes: -1/0/1 = left/center/right , bottom/center/top

	ScrewSites = [
	// [-1,1],[1,1],[1,-1],[-1,-1], // corners
	// [-1,0],[1,0],[0,1],[0,-1] // middles
	[-1,1],[-1,-1],[1,0] // Arduinos
	];

	// ij selectors for frame mounting holes

	MountSites = [
	[0,-1],[0,1],
	// [-1,0],[1,0]
	];

	function ScrewAngle(ij) = (ij[0]ij[1]) ? ij[0]ij[1]*15 : ((!ij[1]) ? 30 : 0); // align screw sides

	OAHeight = FrameHeight + Clearance[2] + PCBSize[2]; // total frame height
	echo(str("OAH: ",OAHeight));

	BossOD = 2*Washer4_40OD; // make bosses oversized for washers

	FlangeExtension = 4.0 + Washer6_32OD/2 – WallThick; // beyond frame structure

	FlangeThick = IntegerMultiple(2.0,ThreadThick); // plate under frame

	Flange = PCBSize
	+ 2*[ScrewOffset,ScrewOffset,0]
	+ [BossOD,BossOD,0]
	+ [2FlangeExtension,2FlangeExtension,(FlangeThick – PCBSize[2])]
	;

	FlangeRadius = BossOD/4;

	echo(str("Flange: ",Flange));
	NumSides = 4*5;

	WireChannel = [Flange[0],15.0,3.0 + PCBSize[2]]; // ad-hoc wiring cutout
	WireChannelOffset = [
	Flange[0]/2,0,(FrameHeight + PCBSize[2] – WireChannel[2]/2)
	];

	//- Adjust hole diameter to make the size come out right

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes

	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

	FiiDia = Dia / cos(180/Sides);

	cylinder(r=(FiiDia + HoleWindage)/2,h=Height,$fn=Sides);
	}

	//- Build things

	if (Layout == "Frame")
	difference() {
	union() { // body block
	translate([0,0,OAHeight/2])
	cube(PCBSize + Clearance + [2WallThick,2WallThick,FrameHeight],center=true);

	for (ij = ScrewSites) // screw bosses
	if (ij[0] != 0 \|\| ij[1] != 0)
	translate([ij[0]*(PCBSize[0]/2 + ScrewOffset),
	ij[1]*(PCBSize[1]/2 + ScrewOffset),
	0])
	cylinder(d=BossOD,h=OAHeight,$fn=NumSides);

	if (ClampFlange) // flange for work holder & mounting screw holes
	linear_extrude(height=Flange[2])
	hull()
	for (i=[-1,1], j=[-1,1]) {
	translate([i(Flange[0]/2 – FlangeRadius),j(Flange[1]/2 – FlangeRadius)])
	circle(r=FlangeRadius,$fn=NumSides); // convenient rounding size
	}
	}

	for (ij = ScrewSites) { // screw position indeies
	if (ij[0] != 0 \|\| ij[1] != 0) {
	translate([ij[0]*(PCBSize[0]/2 + ScrewOffset),
	ij[1]*(PCBSize[1]/2 + ScrewOffset),
	-Protrusion])
	rotate(ScrewAngle(ij))
	PolyCyl(Clear4_40,(OAHeight + 2*Protrusion),6); // screw clearance holes

	translate([ij[0]*(PCBSize[0]/2 + ScrewOffset),
	ij[1]*(PCBSize[1]/2 + ScrewOffset),
	-Protrusion])
	rotate(ScrewAngle(ij))
	PolyCyl(Insert[OD],OAHeight – PCBSize[2] – 3*ThreadThick + Protrusion,6); // inserts

	if (WasherRecess)
	translate([ij[0]*(PCBSize[0]/2 + ScrewOffset),
	ij[1]*(PCBSize[1]/2 + ScrewOffset),
	OAHeight – PCBSize[2]])
	PolyCyl(1.2*Washer4_40OD,(PCBSize[2] + Protrusion),NumSides); // optional washer recess
	}
	}

	if (Mounts)
	for (ij = MountSites)
	translate([ij[0](Flange[0]/2 – Washer6_32OD/2),ij[1](Flange[1]/2 – Washer6_32OD/2),-Protrusion])
	rotate(ScrewAngle(ij))
	PolyCyl(Clear6_32,(Flange[2] + 2*Protrusion),6);

	translate([0,0,OAHeight/2]) // through hole below PCB
	cube(PCBSize – 2[PCBShelf,PCBShelf,0] + [0,0,2OAHeight],center=true);

	translate([0,0,(OAHeight – (PCBSize[2] + Clearance[2])/2 + Protrusion/2)]) // PCB pocket on top
	cube(PCBSize + Clearance + [0,0,Protrusion],center=true);

	if (Channel)
	translate(WireChannelOffset) // opening for wires from bottom side
	cube(WireChannel + [0,0,Protrusion],center=true);
	}

	// Add-on bracket to hold smaller PCB upright at edge

	PCB2Insert = [3.0,4.9,4.1];
	PCB2OC = 45.0;

	if (Layout == "Bracket")
	difference() {
	hull() // frame body block
	for (i=[-1,1]) // bosses around screws
	translate([i*(PCBSize[0]/2 + ScrewOffset),0,0])
	cylinder(r=Washer4_40OD,h=OAHeight,$fn=NumSides);

	for (i=[-1,1]) // frame screw holes
	translate([i*(PCBSize[0]/2 + ScrewOffset),0,-Protrusion])
	rotate(i180/(26))
	PolyCyl(Clear4_40,(OAHeight + 2*Protrusion),6);

	for (i=[-1,1]) // PCB insert holes
	translate([i*PCB2OC/2,(Washer4_40OD + Protrusion),OAHeight/2])
	rotate([90,0,0])
	cylinder(d=PCB2Insert[OD],h=2*(Washer4_40OD + Protrusion),$fn=6);

	}

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The New Hotness

Prototype Board Holder: Now With Mounting Holes and Common Board Sizes