Tag: Sewing

Fabric arts and machines

Epoxy Joint: Test to Destruction

Some years ago, I put the LED power supply for one of the Kenmore 158 machines atop a plastic project box with an adjustable boost supply inside:

Needle LEDs power supply – exterior

The LEDs connected through a coaxial power jack on the far side of the box, held in place with a generous blob of epoxy:

Needle LEDs power supply – interior

A closer look:

Kenmore 158 COB LED – power supply jack

I’m adding a light bar, similar to the one now going onto the Juki TL-2010Q, which needs a direct connection to the 12 VDC supply. Rather than add another coaxial jack, I ripped out the existing jack and installed a DE-9 connector (serial ports being a fading memory by now), giving me an opportunity to test the epoxy joint:

Kenmore 158 COB LED – power supply jack – epoxy bond

Which required grabbing the connector with a pair of pliers and twisting / bending / abusing until it popped free. I don’t know how much grip the scored lines added to the joint, but the connector definitely didn’t give up without a fight; it wasn’t going to fall off on its own.

To be fair, the epoxy had a better grip on the coaxial jack than on the plastic plate, perhaps because the bottom of the jack had all manner of nooks and pins intended for PCB mounting. Ya use what ya got, sez I.

The new connector looks exactly like it should and, because it’s held in place by a pair of screws, should last forever, too:

Kenmore 158 COB LED – power supply

More about all that, later …

2019-02-03

Juki TL-2010Q: COB LED Light Bar

Mary needed more light under the arm of her Juki TL-2010Q sewing machine, so I proposed a 12 V 6 W COB LED module instead of the high-density LED strips I used on her Kenmore 158s:

Kenmore 158 Sewing Machine - Cool white LEDs - rear no flash — Kenmore 158 Sewing Machine – Cool white LEDs – rear no flash

Because the COB LEDs dissipate 6W, far more power than I’m comfortable dumping into a 3D printed structure, I redefined a length of aluminum shelf bracket extrusion to be a heatsink and epoxied the module’s aluminum back plate thereto:

Juki TL-2010Q COB LED - test lighting — Juki TL-2010Q COB LED – test lighting

Unlike the flexible LED strips, the COB LED modules have no internal ballast resistors and expect to run from a constant-current supply. Some preliminary testing showed we’d want less than the maximum possible light output, so a constant-voltage supply and a few ohms of ballast would suffice:

Juki TL-2010Q COB LED - ballast resistor test — Juki TL-2010Q COB LED – ballast resistor test

With all that in hand, the heatsink extrusion cried out for smooth endcaps to control the wires and prevent snagging:

TL-2010Q COB LED Light Bars - end caps - Show layout — TL-2010Q COB LED Light Bars – end caps – Show layout

The central hole in the left cap passes 24 AWG silicone wires from the power supply, with 28 AWG silicone wires snaking down through the L-shaped rectangular cutouts along the extrusion to the LED module’s solder pads.

The model includes built-in support:

TL-2010Q COB LED Light Bars - end caps - Build layout — TL-2010Q COB LED Light Bars – end caps – Build layout

Assuming the curved ends didn’t need support / anchors holding them down turned out to be completely incorrect:

Juki TL-2010Q COB LED - curled endcaps — Juki TL-2010Q COB LED – curled endcaps

Fortunately, those delicate potato chips lived to tell the tale and, after a few design iterations, everything came out right:

Juki TL-2010Q COB LED - heatsink endcap - internal connections — Juki TL-2010Q COB LED – heatsink endcap – internal connections

The “connector”, such as it is, serves to make the light bar testable / removable and the ballast resistor tweakable, without going nuts over the details. The left side is an ordinary pin header strip held in place with hot melt glue atop the obligatory Kapton tape, because the heatsink doesn’t get hot enough to bother the glue. The right side is a pair of two-pin header sockets, also intended for PCB use. The incoming power connects to one set and the ballast resistor to the other, thusly:

Juki TL-2010Q COB LED - light bar connector diagram — Juki TL-2010Q COB LED – light bar connector diagram

The diagram is flipped top-to-bottom from the picture, but you get the idea. Quick, easy, durable, and butt-ugly, I’d say.

The next step was to mount it on the sewing machine and steal some power, but that’s a story for another day.

The relevant dimensions for the aluminum extrusion:

Aluminum shelf bracket extrusion - dimensions — Aluminum shelf bracket extrusion – dimensions

The OpenSCAD source code as a GitHub Gist:

	// Juki TL-2010Q Sewing Machine – COB LED Light Bars
	// Ed Nisley – KE4ZNU
	// 2019-01

	/* [Layout Options] */

	Layout = "Build"; // [Bracket,Endcap,Show,Build]

	Wiring = [1,0]; // left and right wire holes

	BuildSupport = true;

	/* [Extrusion Parameters] */

	ThreadWidth = 0.40;
	ThreadThick = 0.20;

	HoleWindage = 0.2;

	Protrusion = 0.1;

	//—–
	// Shelf bracket used as LED heatsink

	/* [Hidden] */

	LEDPlate = [15.0,2.4]; // 2D coords from end of LED

	BktOuter = [15.9,12.6 + LEDPlate.y]; // 2D coords as seen from end of extrusion
	BktWalls = [1.3,2.2 + LEDPlate.y]; // … extend base to cover LED
	BktCap = [2.5,3.0];

	BracketPoints = [
	[0,0],
	[BktOuter.x,0],
	[BktOuter.x,BktOuter.y],
	[(BktOuter.x – BktCap.x),BktOuter.y],
	[(BktOuter.x – BktCap.x),(BktOuter.y – BktCap.y)],
	[(BktOuter.x – BktWalls.x),(BktOuter.y – BktCap.y)],
	[(BktOuter.x – BktWalls.x),BktWalls.y],
	[BktWalls.x,BktWalls.y],
	[BktWalls.x,(BktOuter.y – BktCap.y)],
	[BktCap.x,(BktOuter.y – BktCap.y)],
	[BktCap.x,BktOuter.y],
	[0,BktOuter.y],
	[0,0]
	];

	BracketPlugInsert = 10.0; // distance into bracket end

	WireOD = 1.6; // COB LED jumpers – 24 AWG silicone
	WireOC = BktOuter.x – 2*BktWalls.x – WireOD;
	echo(str("Wire OC: ",WireOC));

	CableOD = 4.0; // power entry cable

	CapSides = 234;

	//—–
	// 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);
	}

	//—–
	// Endcap with smooth rounding
	// Wires = true to punch holes for LED wires

	module Endcap(Wires = true) {

	// arc length to flatten inside of cap
	// not needed to build in normal orientation

	m = BktOuter.x/2 – sqrt(pow(BktOuter.x/2,2) – pow(BktOuter.x – 2*BktCap.x,2)/4);

	difference() {
	translate([0,0,BktOuter.y/2]) // basic endcap shape
	intersection() {
	cylinder(d=BktOuter.x,h=BktOuter.y,$fn=CapSides,center=true);
	rotate([90,0,0])
	rotate(180/CapSides)
	cylinder(d=BktOuter.y,h=BktOuter.x,$fn=CapSides,center=true);
	}

	translate([-BracketPlugInsert,0,0]) // extrusion + LED plate
	Bracket(BracketPlugInsert);

	if (false) // flatten inner end
	translate([-BktOuter.y + m,0,BktOuter.y/2])
	cube([BktOuter.y,BktOuter.x,BktOuter.y],center=true);

	if (Wires) {
	for (j=[-1,1]) // COB LED connections
	translate([WireOD – BktOuter.x/2,j*WireOC/2,(BktWalls.y + WireOD – Protrusion)/2])
	rotate([0,00,0])
	cube([BktOuter.x,WireOD + Protrusion,BktWalls.y + WireOD + Protrusion],center=true);
	translate([0,0,BktOuter.y/2]) // power entry / exit
	rotate([0,90,0])
	translate([0,0,-BktOuter.x])
	rotate(180/6)
	PolyCyl(CableOD,2*BktOuter.x,6);
	}
	}
	}

	// Totally ad-hoc support structures

	module Support(Wiring = false) {

	Spacing = 4*ThreadWidth;
	NumBars = floor((BktOuter.y/2) / Spacing);
	echo(str("Support bars: ",NumBars));

	color("Yellow") {
	render() difference() {
	union() {
	for (i=[1:NumBars]) // inside extrusion
	translate([-i*Spacing,0,(BktWalls.y + WireOD)/2])
	cube([2ThreadWidth,BktOuter.x – 0BktWalls.x,BktWalls.y + WireOD],center=true);

	if (true)
	for (j=[-1:1]) // reduce outside curve uplift
	translate([0.3BktOuter.y,jBktOuter.x/3,BktOuter.y/10])
	cube([BktOuter.y/3,2*ThreadWidth,BktOuter.y/5],center=true);
	}
	minkowski() { // all-around clearance
	Endcap(Wiring);
	cube(2.0*ThreadThick,center=true);
	}
	if (Wiring) {
	translate([0,0,BktOuter.y/2]) // remove rubble from wire bore
	rotate([0,90,0])
	translate([0,0,-BktOuter.x])
	rotate(180/6)
	PolyCyl(CableOD,2*BktOuter.x,6);
	}
	}

	if (false)
	translate([-(BktOuter.x/4 + ThreadWidth),0,ThreadThick/2]) // adhesion pad
	cube([BktOuter.x/2,BktOuter.x – BktWalls.x,ThreadThick],center=true);

	// translate([BktOuter.x/3,0,ThreadThick/2]) // adhesion pad
	// cube([0.3BktOuter.x,0.7BktOuter.x,ThreadThick],center=true);

	if (false)
	for (j = [-1:1]) // tie pad to bottom of cap
	translate([-(4ThreadWidth)/2,j(BktOuter.x – 2*ThreadWidth)/2,ThreadThick/2])
	cube([4ThreadWidth,2ThreadWidth,ThreadThick],center=true);
	}
	}

	//—–
	// Heatsink extrusion + LED plate
	// Centered on Y with Length extending in +X

	module Bracket(Length = 10)
	translate([0,-BktOuter.x/2,0])
	rotate([90,0,90])
	linear_extrude(height = Length,convexity=3)
	polygon(points=BracketPoints);

	//—–
	// Build things

	if (Layout == "Bracket")
	Bracket();

	if (Layout == "Endcap")
	Endcap();

	if (Layout == "Show") {
	translate([BktOuter.x,0,0])
	Endcap(Wiring[1]);
	translate([-BktOuter.x,0,0])
	rotate(180)
	Endcap(Wiring[0]);
	color("Yellow",0.35)
	translate([-BktOuter.x/2,0,0])
	Bracket(BktOuter.x);
	}

	if (Layout == "Build") {
	translate([BktOuter.y,0,0]) {
	Endcap(Wiring[0]);
	if (BuildSupport)
	Support(Wiring[0]);
	}
	translate([-BktOuter.y,0,0]) {
	Endcap(Wiring[1]);
	if (BuildSupport)
	Support(Wiring[1]);
	}
	}

view raw TL-2010Q COB LED Light Bars.scad hosted with ❤ by GitHub

2019-01-31

Halogen Desk Lamp Conversion

As part of converting the halogen desk lamp to LEDs, I replaced the hulking iron transformer with a flatter counterweight:

Halogen Desk Lamp – 12 V 20 W transformer

Under normal circumstances, you’d use something like steel or lead sheets, but Tiny Bandsaw™ can’t cut any appreciable thickness of steel and I gave away my entire lead stockpile, so I sawed disks from a pile of non-stick pancake griddles and drilled suitable mounting holes:

Parallel clamps in action

Another disk (from a formal aluminum sheet!) goes into the lamp head, with a trio of 3W COB LEDs epoxied in place:

Ex-Halogen Desk Lamp – 3x3W COB LED assembly

The other side of the disk sports a heatsink harvested from a PC, also epoxied in place:

Ex-halogen Desk Lamp – heatsink fitting

Realizing the head required only a little filing to accommodate the heatsink sealed both their fates.

A test firing showed the heatsink needed more airflow, which didn’t come as much of a surprise, so I milled slots in the lamp head:

Ex-halogen Desk Lamp – vent slot milling

Deburring the holes, blackening the sides with a Sharpie, and tucking a bit of black window screen behind the opening made the vents look entirely professional.

The small dome in the base originally cleared the transformer and now holds the entire 10 W LED driver, along with all the wiring, atop the counterweight sheets:

Ex-halogen Desk Lamp – base wiring

A cork pad covers the base for a bit of non-skid action:

Ex-halogen Desk Lamp – cork pad

I couldn’t convince myself filling in those sectors would improve anything, so I didn’t.

And then It Just Worked:

Ex-halogen Desk Lamp – in use

All without a trace of solid modeling or G-Code …

2018-12-07
Kenmore Model 158 Pedal: Graphite Disk Refill

The pedal on one of Mary’s Kenmore Model 158 sewing machines lost most of its speed control abilities, which past experience has shown indicates its carbon / graphite disks have deteriorated. Fortunately, I still have a supply of disks from the Crash Test Dummy machine and have gotten pretty good at dismantling the pedal housing.

While I had the pedal apart, I filed the brass contact plates smooth again:

Kenmore 158 Pedal – graphite disk contact

Most of the deterioration happens within half a dozen disks snuggled up against those contacts, a few more on the other end of the stack against the graphite button applying the pressure, and an occasional grimy disk in the middle of the stack.

I filled both stacks flush to the top of the ceramic housing, then removed one disk from each to let the brass contacts slightly compress the stacks:

Kenmore 158 Pedal – graphite disk refill

A quick test showed the control range started a bit too fast, so I removed one more disk from the stacks, buttoned it up, and it’s all good again: a slow start with a good range.

2018-08-21
Kenmore 158: First Needle LED Failure

The first white LED fixture built to illuminate one of Mary’s Kenmore 158 sewing machines has been in regular use for the last four years:

Kenmore 158 Sewing Machine – mixed LED lighting

We never found a good time to rip-and-replace the “prototype” with brighter SMD LEDs and one of the LEDs finally gave up.

They’re 10 mm white LEDs with five chips wired in parallel, which is obvious when you look into the remaining LED running at 1 mA:

10 mm white LED – chips

The center chip is just dimmer than the others, which means their QC doesn’t tightly control the forward voltage spec.

The wire bonds on the anode terminal of the failed LED look a bit sketchy:

10 mm white LED – wire bonds

Fortunately, I hadn’t removed the 120 VAC wiring for the original bulb and I have two OEM bulbs from other machines, so I just removed my LED gimcrackery, installed a good old incandescent bulb, and she’s back to sewing with a pleasantly warm machine.

The fixture holding the LEDs broke apart as I extracted it, but it’ll never be used again:

10 mm white LED – fixture

The LEDs are rated at 3.5 V and 200 mA (!), but were reasonably bright in series from a 6 V unregulated supply. Perhaps a power glitch killed the poor thing? We’ll never know.

LEDs are reputed to have lifetimes in the multiple tens of thousands of hours, but I’ve seen plenty of failed automotive LEDs and fancy new LED streetlights out there, not to mention many dead and dying traffic signals. Seeing as how they’re in (presumably) well-engineered fixtures with good power supplies and are at most only a few years old, there shouldn’t be any failures yet.

2018-05-23
Quilting Ruler Pivot Pin Sharpening

Mary mentioned the pivot pin supplied with a quilting ruler tended to hang up on the layers of fabric and batting in the quilt squares she’s been making. A quick look showed the pin bore a remarkable resemblance to an ordinary thumb tack:

Ruler Quilting Pivot Pin – as delivered

I reset the pin shaft perpendicular to the head, grabbed a small brass tube in the lathe tailstock, inserted pin in tube, grabbed the head in the chuck, ignored a slight radial offset, and attacked the pin with fine files and sandpaper:

Ruler Quilting Pivot Pin – sharpened

The lathe chuck seemed the easiest way to firmly hold the head; I rotated the chuck by hand while filing.

Most of the remaining scratches go mostly parallel to the pin, but it really didn’t work much better than before. We decided polishing the pin wouldn’t improve the situation enough to make it worthwhile.

That’s the difference between sharp and keen, which cropped up with the cheap ceramic knife from a while ago. The point may penetrate the fabric, but the shaft can’t get through the tight weave.

She’s now using a scary thin and pointy embroidery pin, having successfully rebuffed my offer to mount it in a suitable base.

2018-02-18
Juki TL-2010Q Sewing Machine: Thread Guide

It turns out the thread guide on Mary’s new Juki TL-2010Q sewing machine has what’s euphemistcally known as “negative clearance” with the ruler foot she uses for quilting patterns. With the foot raised to move the cloth, inadvertently pressing the foot pedal or turning the handwheel can crunch the thread guide against the foot.

As you might expect, the intricately bent wire thread guide doesn’t survive the encounter. Not having a spare ready to hand and not knowing quite what it should look like, I reshaped it as best I could:

Juki thread guide – in vise

It worked moderately well:

Juki thread guide – reshaped installed

The automatic needle threader wasn’t reliable, but she could cope until the replacements arrived.

Comparing the new one (left) with the wrecked one (right) shows I didn’t re-bend the loop tightly enough, putting the end on the right at the wrong angle:

Juki thread guide – new vs reshaped

It’s the kind of shape you can duplicate by the thousands with a production machine, but can’t make at home without entirely too much tedious effort.

The new one works fine, seen here in front of a walking foot, with the auto-threader looming in the upper foreground:

Juki thread guide – new installed

Aaaand now we have spares!

2018-02-04