M2 – Page 37 – The Smell of Molten Projects in the Morning

Cheap WS2812 LEDs: Test Fixture Mount

Mounting the ungainly WS2812 LED test fixture seemed like a Good Idea to keep the electricity out of the usual conductive litter:

WS2812 array test fixture - rear — WS2812 array test fixture – rear

The solid model shows more details:

LED Test Fixture - solid model — LED Test Fixture – solid model

The power wires along the array edges slide into the rear (thinner) slot, with enough friction from a few gentle bends to hold the whole mess in place.

The knockoff Arduino Nano rests on the recessed ledge in the pit, with M2 screws and washers at the corners holding it down (the PCB’s built-in holes might work with 1 mm or 0-90 screws, but that’s just crazy talk). I soldered the power wires directly to the coaxial jack pins under the PCB; they snake out to the LEDs through the little trench. There should be another cutout around the USB connector for in-situ programming, although the existing code works fine.

The front (wider) slot holds a piece of translucent white acrylic to diffuse the light:

WS2812 array test fixture - front flash — WS2812 array test fixture – front flash

It’s painfully bright: a few layers of neutral density filter would be appropriate for a desk toy.

The array runs hot enough at MaxPWM = 255 to produce a gentle upward breeze.

It looks even better without the flash:

WS2812 array test fixture - front dark — WS2812 array test fixture – front dark

You’ll find many easier ways to get RGB LED panels, but that’s not the point here; I’m waiting for these things to die an unnatural death.

The OpenSCAD source code as a GitHub Gist:

	// LED Test Fixture
	// Ed Nisley KE4ZNU – February 2017

	ClampFlange = true;

	Channel = false;

	//- Extrusion parameters – must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

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

	Protrusion = 0.1;

	HoleWindage = 0.2;

	//- Screw sizes

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

	Insert = [2.8,3.5,4.0]; // M2 threaded insert
	ScrewOD = 2.0;
	WasherOD = 5.0;

	//- Component sizes

	PCBSize = [18.0,43.5,1.6]; // microcontroller PCB

	PCBClear = 2*[ThreadWidth,ThreadWidth,0]; // clearance around board

	PCBShelf = [ThreadWidth,ThreadWidth,0]; // shelf under perimeter

	PCBCavity = PCBSize – PCBShelf + [0,0,2.5]; // support shelf around bottom parts

	LEDPanel = [70,40,4.0]; // lying flat, LEDs upward
	LEDWire = [LEDPanel[0],LEDPanel[1] + 2*5.0,2.0]; // power wires along sides

	Diffuser = [LEDPanel[0],LEDPanel[1] + 2*4.0,3.5];
	echo(str("Diffuser panel: ",Diffuser));

	WallThick = 8.0;
	BaseThick = 3*ThreadThick + Insert[LENGTH] + PCBCavity[2];

	Block = [3*WallThick + PCBSize[0] + LEDPanel[2] + Diffuser[2],
	2*WallThick + IntegerMultiple(max(PCBSize[1],LEDWire[1]),5),
	BaseThick + LEDPanel[0]];

	echo(str("Block: ",Block));

	CornerRadius = 5.0;
	NumSides = 4*5;

	//- 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);

	FixDia = Dia / cos(180/Sides);

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

	//- Build it

	difference() {

	hull() // main block with rounded corners
	for (i=[-1,1], j=[-1,1])
	translate([i(Block[0]/2 – CornerRadius),j(Block[1]/2 – CornerRadius),,0])
	cylinder(r=CornerRadius,h=Block[2],$fn=NumSides);

	translate([2*WallThick + PCBSize[0] – Block[0],
	0,
	(Block[2]/2 + BaseThick)])
	cube(Block + [0,2*Protrusion,0],center=true); // cut out over PCB

	translate([WallThick + (PCBSize + PCBClear)[0]/2 – Block[0]/2,
	0,
	0]) {
	translate([0,0,(BaseThick + (Protrusion – PCBSize[2])/2)])
	cube(PCBSize + PCBClear + [0,0,Protrusion],center=true); // PCB recess

	translate([0,0,(BaseThick + (Protrusion – PCBCavity[2])/2)])
	cube(PCBCavity + [0,0,Protrusion],center=true); // cavity under PCB

	translate([PCBSize[0]/2 + WallThick/2 – Protrusion/2,PCBSize[1]/2 – 15/2,BaseThick – PCBCavity[2]/2 + Protrusion/2])
	cube([WallThick + PCBShelf[0] + Protrusion,
	15,PCBCavity[2] + Protrusion],center=true); // wiring cutout

	for (i=[-1,1], j=[-1,1]) // screw inserts
	translate([i(PCBSize[0] + ScrewOD)/2,j(PCBSize[1] + ScrewOD)/2,-Protrusion])
	rotate(180/(2*6))
	PolyCyl(Insert[OD],BaseThick + 2*Protrusion,6);
	}

	resize([2*Block[0],0,LEDPanel[0] + Protrusion]) // LED panel outline
	translate([0,0,BaseThick])
	rotate([0,-90,0])
	translate([(LEDPanel[0] + Protrusion)/2,0,0])
	cube(LEDPanel + [Protrusion,0,0],center=true);

	translate([-Block[0]/2 + 2WallThick + PCBSize[0] + LEDWire[2]/2 + 5ThreadWidth,
	0,BaseThick]) // LED wiring recess
	rotate([0,-90,0])
	translate([(LEDWire[0] + Protrusion)/2,0,0])
	cube(LEDWire + [Protrusion,0,0],center=true);


	translate([Block[0]/2 – Diffuser[2]/2 – 5*ThreadWidth,0,BaseThick]) // diffuser
	rotate([0,-90,0])
	translate([(Diffuser[0] + Protrusion)/2,0,0])
	cube(Diffuser + [Protrusion,0,0],center=true);
	}

view raw WS2812 LED Array Test Fixture.scad hosted with ❤ by GitHub

2017-02-24

Bandsaw Worklight: LED Cable Clips

Adapting the sewing machine cable clips for larger USB cables:

LED Cable Clips - solid model — LED Cable Clips – solid model

The calculation positioning the posts wasn’t quite right; they now touch the cable OD at their midline and converge slightly overhead to retain it.

They’re great candidates for sequential printing:

LED Cable Clips - Slic3r - sequential print — LED Cable Clips – Slic3r – sequential print

With the basement at 14 °C, any cooling is too much: the platform heater can’t keep the bed above the thermal cutout temperature, the firmware concludes the thermistor has failed, and shuts the printer off. So I popped the four finished clips off the platform, removed the skirt, unplugged the fan, rebooted that sucker, and restarted the print.

One clip in the front keeps the cable away from the power switch and speed control directly below the gooseneck mount:

USB Gooseneck Mount - cable clip — USB Gooseneck Mount – cable clip

A few clips in the back route the cable from the COB LED epoxied directly onto the bandsaw frame away from the motor enclosure:

Bandsaw platform COB LED - cable clips — Bandsaw platform COB LED – cable clips

They’re mounted on double-sided foam tape. The COB LED on the frame isn’t anything to write home about, but you can see the foam tape peeking out around the clip base:

Unlike those LED filaments, it seems you can gently bend the aluminum substrate under a COB LED.

The bandsaw platform now has plenty of light: a fine upgrade!

Yeah, you can buy stick-on cable anchors, but what’s the fun in that? These fit exactly, hold securely, and work just fine.

The OpenSCAD source code as a GitHub Gist:

	// LED Cable Clips
	// Ed Nisley – KE4ZNU – October 2014
	// February 2017 – adapted for USB cables

	Layout = "Show"; // Show Build

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2; // extra clearance

	Protrusion = 0.1; // make holes end cleanly

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

	//———————-
	// Dimensions

	Base = [15.0,15.0,6*ThreadThick]; // base over sticky square

	CableOD = 3.8;

	BendRadius = 5.0;

	CornerRadius = Base[0]/5;
	CornerSides = 4*4;

	NumSides = 6*3;

	//– Oval clip with central passage

	module OvalPass() {

	intersection() {
	hull()
	for (i=[-1,1], j=[-1,1])
	translate([i(Base[0]/2 – CornerRadius),j(Base[1]/2 – CornerRadius),0])
	rotate(180/CornerSides)
	cylinder(r=CornerRadius,h=Base[2] + 1.00*CableOD,$fn=CornerSides,center=false);

	union() {
	translate([0,0,Base[2]/2]) // oversize mount base
	scale([2,2,1])
	cube(Base,center=true);

	for (j=[-1,1]) // bending ovals
	translate([0,j(Base[1]/2 – 0.125(Base[1] – CableOD)/2),(Base[2] – Protrusion)])
	resize([Base[0]/0.75,0,0])
	cylinder(d1=0.75*(Base[1]-CableOD),
	d2=(Base[1]-CableOD)/cos(0*180/NumSides),
	h=(CableOD + Protrusion),
	center=false,$fn=NumSides);
	}
	}

	if (Layout == "Show")
	color("Red",0.3)
	translate([0,0,Base[2] + CableOD/2])
	rotate([0,90,0])
	cylinder(d=CableOD,h=2*Base[0],center=true,$fn=48);

	}

	//———————-
	// Build it

	OvalPass();

view raw LED Cable Clips.scad hosted with ❤ by GitHub

2017-02-07

Bandsaw Worklight: USB Gooseneck Mount

The bandsaw now sports a chunky mount for its gooseneck light:

USB Gooseneck Mount - on bandsaw — USB Gooseneck Mount – on bandsaw

The gooseneck ends in a USB Type-A plug, so an ordinary USB extension cable can connect it to the hacked hub supplying 9 VDC:

USB Gooseneck Mount - interior — USB Gooseneck Mount – interior

The plastic came from a slightly earlier version of the solid model, with one foam pad under the gooseneck’s USB plug to soak up the clearance. The four smaller holes, with M3 brass inserts visible in the bottom half (on the right), clamp the gooseneck connector in place against the foam; you could push it out if you were really determined, but you’d have to be really determined.

If I ever build another one, it’ll sandwich the plug between opposing pads:

USB Gooseneck Connector Mount - Slic3r preview — USB Gooseneck Connector Mount – Slic3r preview

The lettering on the block stands out much better in the solid model:

USB Gooseneck Connector Mount - solid model - overview — USB Gooseneck Connector Mount – solid model – overview

Obviously, I need help with the stylin’ thing. This looks better, but with terrible overhangs for printing in the obvious no-support orientation:

USB Gooseneck Connector Mount - solid model - rounded top — USB Gooseneck Connector Mount – solid model – rounded top

Anyhow, the USB extension cable (on the left) has plenty of clearance and pulls straight out of the housing, so I can remove the bandsaw cover without unwiring:

USB Gooseneck Mount - assembled — USB Gooseneck Mount – assembled

The LED ticks along at 40 °C in a 14 °C basement, suggesting a thermal coefficient around 14 °C/W. Even in the summer months, with the basement around 25 °C, there’s no risk of PETG softening at 50 °C.

I’ll epoxy a similar 1.8 W COB LED onto the curve of the bandsaw frame where it can shine on the left and rear part of the table; it doesn’t even need a case.

The OpenSCAD source code as a GitHub Gist:

	// Gooseneck lamp for MicroMark bandsaw
	// Ed Nisley KE4ZNU
	// February 2017

	Layout = "Mount"; // Mount Show Build

	Gap = 5; // distance between halves for Show

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———————-
	// Dimensions

	Tap10_32 = 0.159 * inch;
	Clear10_32 = 0.190 * inch;
	Head10_32 = 0.373 * inch;
	Head10_32Thick = 0.110 * inch;
	Nut10_32Dia = 0.433 * inch;
	Nut10_32Thick = 0.130 * inch;
	Washer10_32OD = 0.381 * inch;
	Washer10_32ID = 0.204 * inch;

	ID = 0; // for round things
	OD = 1;
	LENGTH = 2;

	Insert = [3.0,4.9,2*ThreadThick + IntegerMultiple(4.2,ThreadThick)]; // M3 short brass insert

	CornerRadius = 5.0; // rounded mount block corners for pretty
	CornerSides = 4*4;

	RoundedTop = true; // true for fancy smooth top edges

	USBPlug = [39.0,16.0,8.3]; // plug, X from base of plug
	USBSocket = [28.0,20.0,11.5]; // USB extension, X from tip of socket

	USBMating = [-12.0,0,0]; // offset of plug base relative to block center

	Foam = [35.0,10.0,2.0 – 1.0]; // foam pad to secure USB plug (Z = thickness – compression)

	GooseneckOD = 5.0; // flexy gooseneck diameter

	MountScrewOC = 35.0; // make simple screw hole spacing for bandsaw case

	MountBlock = [10*round((USBPlug[0] + USBSocket[0] + 5.0)/10),
	10*round((MountScrewOC + Washer10_32OD + 5.0)/10),
	// 26ThreadThick + IntegerMultiple(max(USBPlug[2],USBSocket[2]),ThreadThick)];
	16.0]; // thickness = 16 mm M3x0.5 button head screw

	echo(str("Block size: ",MountBlock));

	LegendDepth = 2*ThreadThick; // lettering depth

	//———————-
	// Useful routines

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

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

	FixDia = Dia / cos(180/Sides);

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

	//– Mount

	module Mount() {

	difference() {
	hull()
	if (RoundedTop) {
	for (i=[-1,1], j=[-1,1])
	translate([i(MountBlock[0]/2 – CornerRadius),j(MountBlock[1]/2 – CornerRadius),0]) {
	translate([0,0,-MountBlock[2]/2])
	rotate(180/CornerSides)
	cylinder(r=CornerRadius,h=MountBlock[2]/2,$fn=CornerSides,center=false);
	translate([0,0,MountBlock[2]/2 – CornerRadius])
	rotate(180/CornerSides)
	sphere(r=CornerRadius,$fn=CornerSides,center=true);
	}
	}
	else {
	for (i=[-1,1], j=[-1,1])
	translate([i(MountBlock[0]/2 – CornerRadius),j(MountBlock[1]/2 – CornerRadius),0])
	rotate(180/CornerSides)
	cylinder(r=CornerRadius,h=MountBlock[2],$fn=CornerSides,center=true);
	}
	for (j=[-1,1]) // screws into bandsaw case
	translate([0,j*MountScrewOC/2,-(MountBlock[2]/2 + Protrusion)])
	rotate(180/8)
	PolyCyl(Clear10_32,(MountBlock[2] + 2*Protrusion),8);
	for (i=[-1,1], j=[-1,1]) { // clamp screws
	translate([iMountBlock[0]/4,jMountScrewOC/2,-MountBlock[2]])
	PolyCyl(Insert[ID],2*MountBlock[2],6); // clearance
	translate([iMountBlock[0]/4,jMountScrewOC/2,-(MountBlock[2]/2 + Protrusion)])
	PolyCyl(Insert[OD],Insert[LENGTH] + Protrusion,6); // inserts
	}
	rotate([0,90,0]) // gooseneck flexy cable
	rotate(180/6)
	PolyCyl(GooseneckOD,MountBlock[0],6);

	translate([USBPlug[0]/2,0,0] + USBMating – [Protrusion/2,0,0]) // USB plug outline
	cube(USBPlug + [Protrusion,0,0],center=true);
	translate([-USBSocket[0]/2,0,0] + USBMating) // USB socket outline
	cube(USBSocket,center=true);

	translate([(Foam[0]/2 + 5*ThreadWidth),0,-(Foam[2]/2 + USBPlug[2]/2)] + USBMating – [Protrusion,0,-Protrusion]/2) // foam padding recess
	cube(Foam + [Protrusion,0,Protrusion],center=true); // foam packing
	translate([(Foam[0]/2 + 5*ThreadWidth),0, (Foam[2]/2 + USBPlug[2]/2)] + USBMating – [Protrusion,0, Protrusion]/2) // foam padding recess
	cube(Foam + [Protrusion,0,Protrusion],center=true);

	render(convexity=5)
	translate([0,0,MountBlock[2]/2 – LegendDepth])
	linear_extrude(height=LegendDepth + Protrusion) {
	translate([0,5,0])
	text(text="KE4ZNU",size=8,spacing=1.10,font="Bitstream Vera Sans:style=Bold",valign="center",halign="center");
	translate([0,-5,0])
	text(text="4 Feb 2017",size=6,spacing=1.05,font="Bitstream Vera Sans:style=Bold",valign="center",halign="center");
	}
	}
	}

	//———————-
	// Build it

	if (Layout == "Mount") {
	Mount();
	}

	if (Layout == "Show") {
	translate([0,0,-Gap/2])
	difference() {
	Mount();
	translate([0,0,MountBlock[2]])
	cube(2*MountBlock,center=true);
	}
	translate([0,0,Gap/2])
	difference() {
	Mount();
	translate([0,0,-MountBlock[2]])
	cube(2*MountBlock,center=true);
	}
	}

	if (Layout == "Build") {
	translate([0,0.6*MountBlock[1],MountBlock[2]/2])
	difference() {
	Mount();
	translate([0,0,MountBlock[2]])
	cube(2*MountBlock,center=true);
	}
	translate([0,-0.6*MountBlock[1],MountBlock[2]/2])
	rotate([180,0,0])
	difference() {
	Mount();
	translate([0,0,-MountBlock[2]])
	cube(2*MountBlock,center=true);
	}
	}

view raw USB Gooseneck Connector Mount.scad hosted with ❤ by GitHub

2017-02-06

Proto Board Holders: 80×120 mm

Another stack of proto boards arrived, this time 80×120 mm, and I ran off another pair of holders:

Proto Board Holder - 80x120 - tooling — Proto Board Holder – 80×120 – tooling

Not wanting to, ahem, screw around with the lathe, the screws got themselves shortened the old-fashioned way: by hand, with the screw cutter, then filed and passed through a 4-40 die to clean up the threads.

Bah!

2017-02-05

Bandsaw Worklight

Having hacked back the end of the USB gooseneck extension, a tweak of the COB LED heatsink mount for my desk lamp produces a smaller version for a 1.8 W LED:

Chip On Board Heatsink Mount - Bandsaw Lamp - solid model — Chip On Board Heatsink Mount – Bandsaw Lamp – solid model

That fits half of a random heatsink, bandsawed just to the far side of the middle fin and milled flat.

Ream out the 5 mm hole with a #8 drill for a snug fit around the gooseneck, jam gooseneck in place, dab epoxy on the corners of the recess, mash the heatsink in place, solder wires to LED, smear epoxy on the aluminum backplate, clamp while curing:

USB Gooseneck - LED assembly — USB Gooseneck – LED assembly

And it looks pretty good, if I do say so myself:

USB Gooseneck - on bandsaw — USB Gooseneck – on bandsaw

The hook-n-loop tape holding the cable to the bandsaw gotta go, but should suffice until I conjure a better mount.

The alert reader may wonder how a 9 V COB LED runs from a 5 V USB cable with nary a trace of a voltage booster to be seen. Well, that’s not really a USB cable any more; I paralleled the red+white and black+green wires for lower resistance, then hacked a 9 VDC power supply into an old USB hub:

Hacked USB hub - PCB mods — Hacked USB hub – PCB mods

I ripped out the upstream USB plug, hotwired the 9 V supply where the 5 V USB wires used to be, soldered jumpers on the downstream sockets to short the outer two pin pairs together, razor-knifed the power leads going into the epoxy-blobbed USB controller, and declared victory:

Hacked USB hub - in use — Hacked USB hub – in use

Admittedly, that “In Use” LED runs a bit brighter now.

I have a few other tools on that bench in need of LED lights; when I build ’em, they can all plug into this hub. No reason to invent new connectors & cables & all that. It may need a power switch.

Turns your stomach, eh?

The OpenSCAD source code as a GitHub Gist:

	// Chip-on-board LED light heatsink mount for desk lamp
	// Ed Nisley KE4ZNU December 2015
	// February 2017 – rectangular COB, smaller heatsink

	Layout = "Show"; // Show Build

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———————-
	// Dimensions

	ID = 0; // for round things
	OD = 1;
	LENGTH = 2;

	Gooseneck = [3.0,5.0,15.0]; // anchor for end of gooseneck

	COB = [30.0,11.0,2.5]; // Chip-on-board LED module

	Heatsink = [37.1,19.2,10.0]; // overall
	HeatsinkBase = 2.0; // solid base below fins

	HSLip = 1.0; // width of lip under heatsink

	BaseMargin = 22ThreadWidth;
	BaseRadius = 3*ThreadThick + Gooseneck[OD]/2; // defines slab thickness
	BaseSides = 2*4;

	Base = [(Gooseneck[LENGTH] + Gooseneck[OD] + Heatsink[0] + 2*BaseRadius + BaseMargin),
	(Heatsink[1] + 2BaseRadius + 2BaseMargin),
	2*BaseRadius];

	echo(str("Slab thickness: ",Base[2]));

	//———————-
	// Useful routines

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

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

	FixDia = Dia / cos(180/Sides);

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

	//– Lamp heatsink mount

	module Lamp() {

	difference() {
	translate([(Base[0]/2 – BaseRadius – Gooseneck[LENGTH]),0,0])
	hull()
	for (i=[-1,1], j=[-1,1])
	translate([i(Base[0]/2 – BaseRadius),j(Base[1]/2 – BaseRadius),Base[2]/2])
	sphere(r=BaseRadius/cos(180/BaseSides),$fn=BaseSides);

	translate([(Heatsink[0]/2 + Gooseneck[OD]), // main heatsink recess
	0,
	(Base[2] + Heatsink[2]/2 – HeatsinkBase)])
	cube((Heatsink + [HoleWindage,HoleWindage,0.0]),center=true);

	translate([(Heatsink[0]/2 + Gooseneck[OD]),0,HeatsinkBase]) // lower lip to shade lamp module
	scale([1,1,2])
	cube(Heatsink – [2HSLip,2HSLip,0],center=true);

	translate([0,0,Base[2]/2]) // goooseneck insertion
	rotate([0,-90,0]) rotate(180/8)
	PolyCyl(Gooseneck[OD],Base[0],8);

	translate([0,0,Base[2]/2 + Gooseneck[ID]/2]) // wire exit
	rotate([180,0,0])
	PolyCyl(Gooseneck[ID],Base[2],6);

	translate([Gooseneck[OD],0,(Base[2] – HeatsinkBase – Protrusion)/2]) // wire slot
	rotate([180,0,0])
	cube([2*Gooseneck[OD],Gooseneck[ID],(Base[2] – HeatsinkBase + Protrusion)],center=true);

	}

	}

	//———————-
	// Build it

	if (Layout == "Show") {
	Lamp();
	}

	if (Layout == "Build") {

	}

view raw Chip On Board Heatsink Mount.scad hosted with ❤ by GitHub

2017-02-04

60 kHz Preamp: Board Holder

A cleaned up version of my trusty circuit board holder now keeps the 60 kHz preamp off what passes for a floor in the attic:

The solid model became slightly taller than before, due to a serious tangle of wiring below the board, with a narrower flange that fits just as well in the benchtop gripper:

Proto Board - 80x110 — Proto Board – 80×110

Tidy brass inserts epoxied in the corners replace the previous raw screw holes in the plastic:

Proto Board Holder - 4-40 inserts and screws — Proto Board Holder – 4-40 inserts and screws

The screws standing on their heads have washers epoxied in place, although that’s certainly not necessary; the dab of left-over epoxy called out for something. The screws got cut down to 7 mm after curing.

The preamp attaches to a lumpy circle of loop antenna hung from the rafters and returns reasonable results:

WWVB - morning - 2017-01-16 — WWVB – morning – 2017-01-16

The OpenSCAD source code as a GitHub Gist:

	// Test support frame for proto boards
	// Ed Nisley KE4ZNU – Jan 2017

	ClampFlange = true;

	Channel = false;

	//- Extrusion parameters – must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

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

	Protrusion = 0.1;

	HoleWindage = 0.2;

	//- Screw sizes

	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;

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

	Insert = [3.9,4.6,5.8];

	//- PCB sizes

	PCBSize = [110.0,80.0,1.5];
	PCBShelf = 2.0;

	Clearance = 2*[ThreadWidth,ThreadWidth,0];

	WallThick = 5.0;
	FrameHeight = 10.0;

	ScrewOffset = 0.0 + Clear4_40/2;

	ScrewSites = [[-1,1],[-1,1]]; // -1/0/+1 = left/mid/right and bottom/mid/top

	OAHeight = FrameHeight + Clearance[2] + PCBSize[2];

	FlangeExtension = 3.0;
	FlangeThick = IntegerMultiple(2.0,ThreadThick);
	Flange = PCBSize
	+ 2*[ScrewOffset,ScrewOffset,0]
	+ 2*[Washer4_40OD,Washer4_40OD,0]
	+ [2FlangeExtension,2FlangeExtension,(FlangeThick – PCBSize[2])]
	;

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

	WireChannel = [Flange[0],15.0,3.0 + PCBSize[2]];
	WireChannelOffset = [Flange[0]/2,25.0,(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);

	FixDia = Dia / cos(180/Sides);

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

	//- Build it

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

	for (x=[-1,1], y=[-1,1]) { // screw bosses
	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	0])
	cylinder(r=Washer4_40OD,h=OAHeight,$fn=NumSides);
	}

	if (ClampFlange) // flange for work holder
	linear_extrude(height=Flange[2])
	hull()
	for (i=[-1,1], j=[-1,1]) {
	translate([i(Flange[0]/2 – Washer4_40OD/2),j(Flange[1]/2 – Washer4_40OD/2)])
	circle(d=Washer4_40OD,$fn=NumSides);
	}
	}

	for (x=[-1,1], y=[-1,1]) { // screw position indexes

	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	-Protrusion])
	rotate(xy180/(2*6))
	PolyCyl(Clear4_40,(OAHeight + 2*Protrusion),6); // screw clearance holes

	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	OAHeight – PCBSize[2] – Insert[LENGTH]])
	rotate(xy180/(2*6))
	PolyCyl(Insert[OD],Insert[LENGTH] + Protrusion,6); // inserts

	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	OAHeight – PCBSize[2]])
	PolyCyl(1.2*Washer4_40OD,(PCBSize[2] + Protrusion),NumSides); // washers
	}

	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);
	}

view raw Proto Board Holder.scad hosted with ❤ by GitHub

2017-01-24

Loop Antenna Splice Reinforcement

Those solder joints and finicky little wires seem much too fragile on their own:

LF Loop Antenna - complete joint — LF Loop Antenna – complete joint

This should help:

Loop Antenna Splice - assembled — Loop Antenna Splice – assembled

Foam blocks hold the ribbon cable in place and provide a bit of strain relief around the hard plastic edge:

Loop Antenna Splice - hardware — Loop Antenna Splice – hardware

The brass inserts in the bottom block (on the left) got epoxied in place, because they must provide quite a bit of force to clamp the foam. Their larger knurled end sits flush with the outside surface and the smaller end has one thread thickness of clearance below the inner surface.

A last look at the wiring:

Loop Antenna Splice - wiring — Loop Antenna Splice – wiring

I think the preamp must sit at some distance from the antenna to prevent feedback, but that remains to be seen.

The M2’s nozzle accumulated a huge blob of PETG that turned into a giant smear:

Loop Antenna Splice - PETG booger — Loop Antenna Splice – PETG booger

Fortunately, it’s on the inside where nobody will ever see it. If you know where to look, it’s barely visible from the outside.

The solid model shows off the structure a bit better:

Loop Antenna Splice - show view — Loop Antenna Splice – show view

The inside view:

Loop Antenna Splice - bottom — Loop Antenna Splice – bottom

The OpenSCAD source code as a GitHub Gist:

	// Ribbon cable loop antenna splice
	// Ed Nisley KE4ZNU December 2016

	Layout = "Text";

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———-
	// Dimensions

	Cable = [200,48.0,1.5]; // X = longer than anything else

	Splice = [15.0,53.0,5.0]; // epoxy blob around joints

	Foam = [15.0,Splice[1],2.0];
	CornerRadius = 5.0;

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

	Insert = [3.9,4.6 – 0.1,5.8]; // 4-40 knurled brass insert

	Screw = [2.7,5.5,2.0]; // OD = head LENGTH = head thickness
	Washer = [3.0,8.0,0.8];

	BlockOA = [60.0, // convenient length
	Splice[1] + 4*Washer[OD], // clearance around washer on top
	2(Insert[LENGTH] + 2ThreadThick)]; // insert sets both thicknesses

	NumScrews = 2; // screws along each side of cable
	ScrewOC = [BlockOA[0] / NumScrews,
	BlockOA[1] – 2*Washer[OD],
	2*BlockOA[2] // ensure complete holes
	];

	TextThick = 3*ThreadThick; // depth of text into surface
	TextFit = HoleWindage/2; // clearance around text polygons

	//———————-
	// Useful routines

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
	FixDia = Dia / cos(180/Sides);
	cylinder(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
	}

	//—–
	// Blocky model of cable + splice + wire tap for subtraction

	module Antenna() {
	union() {
	cube(Cable,center=true);
	cube(Splice,center=true);
	for (i=[-1,1])
	translate([0,-Splice[1]/2,0])
	cube([Splice[0]/2,Splice[1],2*Foam[2]],center=true);
	}
	}

	// Outside shape of splice Block, less screw clearance

	module SpliceBlock() {
	difference() {
	hull()
	for (i=[-1,1], j=[-1,1])
	translate([i(BlockOA[0]/2 – CornerRadius),j(BlockOA[1]/2 – CornerRadius),-BlockOA[2]/2])
	cylinder(r=CornerRadius,h=BlockOA[2],$fn=4*8);
	for (i = [0:NumScrews – 1], j=[-1,1])
	translate([-BlockOA[0]/2 + ScrewOC[0]/2 + iScrewOC[0],jScrewOC[1]/2,-(BlockOA[2]/2 + Protrusion)])
	PolyCyl(Screw[ID],BlockOA[2] + 2*Protrusion,6);
	}
	}

	// Splice block less cable

	module ShapedBlock() {
	difference() {
	SpliceBlock();
	Antenna();
	}
	}

	// Bottom

	module BottomPlate() {
	difference() {
	ShapedBlock();
	translate([0,0,BlockOA[2]/2])
	cube(BlockOA + 2*[Protrusion,Protrusion,0],center=true);
	Antenna(Splice);
	for (i = [0:NumScrews – 1], j=[-1,1])
	translate([-BlockOA[0]/2 + ScrewOC[0]/2 + iScrewOC[0],jScrewOC[1]/2,-(BlockOA[2]/2 + Protrusion)])
	PolyCyl(Insert[OD],2*Insert[LENGTH],6);
	for (i=[-1,1])
	translate([i*((BlockOA[0] – Foam[0] + Protrusion)/2),0,(BlockOA[2]/2 – Cable[2]/2 – Foam[2])])
	cube([Foam[0] + Protrusion,Foam[1],BlockOA[2]],center=true);
	}
	}

	// Top

	module TopPlate() {
	difference() {
	ShapedBlock();
	translate([0,0,-BlockOA[2]/2])
	cube(BlockOA + 2*[Protrusion,Protrusion,0],center=true);
	Antenna(Splice);
	for (i=[-1,1])
	translate([i*((BlockOA[0] – Foam[0] + Protrusion)/2),0,-(BlockOA[2]/2 – Cable[2]/2 – Foam[2])])
	cube([Foam[0] + Protrusion,Foam[1],BlockOA[2]],center=true);
	rotate(90) {
	translate([0,6,BlockOA[2]/2 – TextThick])
	TextHack("KE4ZNU",8,0.0,1.15,TextThick + Protrusion);
	translate([0,-6,BlockOA[2]/2 – TextThick])
	TextHack("2016·12",6,0.0,1.20,TextThick + Protrusion);
	}
	}
	}

	module TextHack(Text="sample",Size=10,Offset=0.0,Space=1.0,Thick=ThreadThick) {
	linear_extrude(height=Thick,convexity=10)
	offset(r=Offset)
	text(Text,font=":bold",size=Size,spacing=Space,halign="center",valign="center");
	}


	//———-
	// Build them

	if (Layout == "Antenna")
	Antenna();

	if (Layout == "SpliceBlock")
	SpliceBlock();

	if (Layout == "ShapedBlock")
	ShapedBlock();

	if (Layout == "Bottom")
	BottomPlate();

	if (Layout == "Top")
	TopPlate();

	if (Layout == "Text") {
	translate([0,6,0])
	TextHack("KE4ZNU",8,-TextFit,1.15,TextThick);
	translate([0,-6,0])
	TextHack("2016·12",6,-TextFit,1.20,TextThick);
	}

	if (Layout == "Show") {
	translate([0,0,5])
	TopPlate();
	translate([0,0,-5])
	BottomPlate();
	color("Orange",0.2)
	Antenna();
	}

	if (Layout == "Build") {
	translate([0,-0.6*BlockOA[1],BlockOA[2]/2])
	rotate([180,0,0])
	TopPlate();
	translate([0,0.6*BlockOA[1],BlockOA[2]/2])
	BottomPlate();
	}

view raw Loop Antenna Splice.scad hosted with ❤ by GitHub

2016-12-27

Tag: M2

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Loop Antenna Splice Reinforcement