Improvements – Page 139 – 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

Vacuum Tube Lights: Plate Wire Plug

After replacing the WS2812 LED in the 21HB5A socket, I drilled out the hole in the disk platter for a 3.5 mm stereo jack, wired a nice knurled metal plug onto the plate lead, and it’s all good:

21HB5A - Audio plug cable — 21HB5A – Audio plug cable

The plug had a rather large cable entry that cried out for a touch of brass:

Audio plug - brass trim turning — Audio plug – brass trim turning

Fancy plugs have a helical spring strain relief insert about the size & shape of that brass snout; might have to buy me some fancy plugs.

This time, I got the alignment right by clamping everything in the lathe while the epoxy cured:

Audio plug - brass trim gluing — Audio plug – brass trim gluing

I flipped the drill end-for-end, which was surely unnecessary.

It’s now sitting on the kitchen table, providing a bit of light during supper while I wait for a WS2812 controller failure. Again.

2017-02-21

Screw Cutting Fixture vs. Lathe Ways

A length of aluminum hex bar became a nice 10-32 screw trimmer:

Screw cutting fixture - 10-32 - first cut — Screw cutting fixture – 10-32 – first cut

The hex neatly fits a 5/8 inch wrench, so I can tighten the jam nuts enough to run the lathe forward, part off the screw, and clean up the end just fine.

Unfortunately, the second test cut didn’t work nearly so well:

Screw cutting fixture - 10-32 - wrecked — Screw cutting fixture – 10-32 – wrecked

With the cross-slide gib adjusted to the snug side of easy, the cut put enough pressure on the parting tool to lift the way on the tailstock side about 4 mil = 0.1 mm. The parting tool submarined under the cut, dislodged the fixture, and didn’t quite stall the motor while the chuck jaws ate into the aluminum.

Well, that was a learning experience.

After tightening the cross-slide gib to the far side of hard-to-turn:

Put a longer screw in the fixture
Grab it in the tailstock drill chuck
Crunch the hex end of the fixture in the spindle chuck
Remove the screw through the spindle (*)
Put a slight taper on the end of the fixture threads with a center drill
Deploy the live center to support the fixture

Like this:

Screw cutting fixture - 10-32 - rechucked — Screw cutting fixture – 10-32 – rechucked

Turns out that angling the bit by 10° dramatically reduces chatter. If I had BR and BL turning tools, I’d be using them with the QCTP set to 0°, but they weren’t included in the set that came with the lathe.

It’s a good thing I’m not fussy about the diameter of that cylindrical section:

Screw cutting fixture - 10-32 - reshaped — Screw cutting fixture – 10-32 – reshaped

I knew the craptastic lathe ways needed, mmmm, improvement and it’s about time to do something.

(*) By concatenating all my ¼ inch socket extension bars into an absurd noodle capped with square-to-hex adapter holding a Philips bit.

2017-02-17

Improved Cable Clips

Those ugly square cable clips cried out for a cylindrical version:

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

Which prompted a nice button:

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

Which suggested the square version needed some softening:

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

Apart from the base plate thickness, all the dimensions scale from the cable OD; I’ll be unsurprised to discover small cables don’t produce enough base area for good long-term foam tape adhesion. Maybe the base must have a minimum size or area?

I won’t replace the ones already on the saw, but these will look better on the next project…

The OpenSCAD source code as a GitHub Gist:

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

	Layout = "Show"; // Show Build

	Style = "Button"; // Square Round Button

	//- 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

	CableOD = 3.8; // cable jacket

	Base = [4CableOD,4CableOD,3*ThreadThick]; // overall base and slab thickness

	CornerRadius = CableOD/2; // radius of square corners
	CornerSides = 4*4; // total sides on square corner cylinders

	NumSides = 6*3; // total sides for cylindrical base

	//– Oval clip with central passage

	module CableClip() {

	intersection() {
	if (Style == "Square")
	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] + CableOD/2,$fn=CornerSides,center=false);
	translate([0,0,Base[2] + CableOD/2])
	sphere(d=CableOD,$fn=CornerSides);
	}
	else if (Style == "Round")
	cylinder(d=Base[0],h=Base[2] + 1.00*CableOD,$fn=NumSides);
	else if (Style == "Button")
	resize(Base + [0,0,2*(Base[2] + CableOD)])
	sphere(d=Base[0],$fn=NumSides);

	union() {
	translate([0,0,Base[2]/2]) // base defines slab thickness
	cube(Base,center=true);

	for (j=[-1,1]) // retaining 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("Green",0.2)
	translate([0,0,Base[2] + CableOD/2])
	rotate([0,90,0])
	cylinder(d=CableOD,h=2*Base[0],center=true,$fn=48);

	}

	//———————-
	// Build it

	CableClip();

view raw Cable Clips.scad hosted with ❤ by GitHub

2017-02-16

Screw Cutting Fixture: Full-thread Aluminum

By and large, when you follow the recipe, you get the expected result:

Screw cutting fixture - M3x0.5 aluminum - side view — Screw cutting fixture – M3x0.5 aluminum – side view

That’s another length of the same aluminum rod, this time with a full-length M3x0.5 thread down the middle, and a screw with a neatly trimmed end.

Running the lathe spindle in reverse prevents the screw from loosening the jam nuts on the left:

Screw cutting fixture - M3x0.5 aluminum - in lathe chuck — Screw cutting fixture – M3x0.5 aluminum – in lathe chuck

Running the spindle forward does move the screw enough to loosen the nuts. Perhaps I should put wrench flats on the big end of the fixture so I can really torque the nuts.

That front nut was mostly decorative, rather than tight, because I didn’t expect the first attempt to work nearly as well as it did. A bit of filing to taper the end of the thread and it was all good.

That was easy…

2017-02-14

Blog Backup: Incremental Media

The recipe for incrementally copying media files since the previous blog backup works like this:

grep attachment_url *xml > attach.txt
sed 's/^.*http/http/' attach.txt | sed 's/<\/wp.*//' > download.txt
wget -nc -w 2 --no-verbose --random-wait --force-directories --directory-prefix=Media/ -i download.txt

The -nc sets the “no clobber” option, which (paradoxically) simply avoids downloading a duplicate of an existing file. Otherwise, it’d download the file and glue on a *.1 suffix, which isn’t a desirable outcome. The myriad (thus far, 0.6 myriad) already-copied files generate a massive stream of messages along the lines of File ‘mumble’ already there; not retrieving.

Adding --no-verbose will cut the clutter and emit some comfort messages.

There seems no way to recursively fetch only newer media files directly from the WordPress file URL with -r -N; the site redirects the http:// requests to the base URL, which doesn’t know about bare media files and coughs up a “not found” error.

2017-02-11

MicroMark Bandsaw: Blackened Table

The really bright LED worklights I added to the MicroMark bandsaw produced plenty of glare from the raw aluminum table top:

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

No good deed goes unpunished, I suppose.

While rooting around for something else, I rediscovered my bottle of Birchwood Casey Aluminum Black (basically selenium dioxide) that’s intended for touchup work on small parts, not blackening an entire aluminum plate. Well, having had that bottle forever, it’s not like I’ll miss a few milliliters.

If this didn’t work, I could always sand the table down to the original aluminum finish.

So I applied a sanding block in hopes of smoothing the tooling marks:

MicroMark Bandsaw - sanded table — MicroMark Bandsaw – sanded table

Looked pretty good, I thought, so:

Wipe it down with alcohol (per the bottle instructions)
Slather on a generous dose of Aluminum Black
Let that chew on the table for a minute
Rinse off with water, wipe dry
Perch atop the furnace for thorough drying
Spray with Topsaver oil, wipe down
Put it back on the bandsaw

Aaaaand it looks great:

MicroMark Bandsaw - blackened table — MicroMark Bandsaw – blackened table

Well, in terms of metal finishing, that blackening job looks downright crappy. Aluminium Black is intended for decorative work and will surely wear quickly on the bandsaw table, but it’s entirely good enough for my simple needs: the glare from those lights is gone.

After I took the picture, I blackened the brass screw in the slot. Came out a weird mottled green-bronze, might look antique in a different context, suits me just fine.

Done!

2017-02-10