Improvements – Page 74 – The Smell of Molten Projects in the Morning

LTSpice Diode Models Sorted By Forward Voltage

LTSpice includes a bunch of LEDs I’ll never own, so finding a tabulation of their forward voltages helped match them against various LEDs on hand. The table was sorted by the forward voltage at the diode’s rated average current, which wasn’t helpful for my simple needs, so I re-sorted it on the Vf @ If = 20 mA column over on the right:

Part #       Mfg             Is         N      Iavg Vf@Iavg  Vd@If
QTLP690C     Fairchild    1.00E-22    1.500    0.16   1.90    1.82
PT-121-B     Luminous     4.35E-07    8.370   20.00   3.84    2.34
LUW-W5AP     OSRAM        6.57E-08    7.267    2.00   3.26    2.39
LXHL-BW02    Lumileds     4.50E-20    2.600    0.40   2.95    2.75
W5AP-LZMZ-5K Lumileds     3.50E-17    3.120    2.00   3.13    2.76
LXK2-PW14    Lumileds     3.50E-17    3.120    1.60   3.11    2.76
AOT-2015     AOT          5.96E-10    6.222    0.18   3.16    2.80
NSSW008CT-P  Nichia       2.30E-16    3.430    0.04   2.92    2.86
NSSWS108T    Nichia       1.13E-18    3.020    0.04   2.99    2.94
NSPW500BS    Nichia       2.70E-10    6.790    0.03   3.27    3.20
NSCW100      Nichia       1.69E-08    9.626    0.03   3.60    3.50

The currents come from plugging the various constants into the Schockley Diode Equation and turning the crank.

One could, of course, measure the constants for the diodes on hand to generate a proper Spice model, but that seems like a lot of work for what’s basically a blinking LED.

2020-08-28

Quilting Hexagon Template Generator: Knobless Half-Triangle

Although I’d put the same knob on the half-triangle end piece template as on the equilateral triangle template for piecing hexagons into strips, Mary decided a flat chip would be easier to use:

Quilting Hex Template - family - knobless half-triangle — Quilting Hex Template – family – knobless half-triangle

Bonus: you can now flip it over to cut the other half-triangles, if you haven’t already figured out how to cut two layers of fabric folded wrong sides together.

While I was at it, the knob on the triangle became optional, too. Flipping that one doesn’t buy you much, though.

The OpenSCAD source as a GitHub Gist has been ever so slightly tweaked:

	// Quilting – Hexagon Templates
	// Ed Nisley KE4ZNU – July 2020
	// Reverse-engineered to repair a not-quite-standard hexagon quilt
	// Useful geometry:
	// https://en.wikipedia.org/wiki/Hexagon

	/* [Layout Options] */

	Layout = "Build"; // [Build, HexBuild, HexPlate, TriBuild, TriPlate, EndBuild, EndPlate]

	//——-
	//- Extrusion parameters must match reality!
	// Print with 2 shells

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleFinagle = 0.2;
	HoleFudge = 1.00;

	function HoleAdjust(Diameter) = HoleFudge*Diameter + HoleFinagle;

	Protrusion = 0.1; // make holes end cleanly

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

	inch = 25.4;

	//——-
	// Dimensions

	/* [Layout Options] */

	FinishedWidthInch = 2.75;
	FinishedWidth = FinishedWidthInch * inch;

	SeamAllowanceInch = 0.25;
	SeamAllowance = SeamAllowanceInch * inch;

	TemplateThick = 3.0;

	TriKnob = true;
	EndKnob = false;

	/* [Hidden] */

	FinishedSideInch = FinishedWidthInch/sqrt(3);
	FinishedSide = FinishedSideInch * inch;

	echo(str("Finished side: ",FinishedSideInch," inch"));

	CutWidth = FinishedWidth + 2*SeamAllowance;

	CutSide = CutWidth/sqrt(3);
	echo(str("Cut side: ",CutSide / inch," inch"));

	// Make polygon-circles circumscribe the target widths

	TemplateID = FinishedWidth / cos(180/6);
	TemplateOD = CutWidth / cos(180/6);

	/* [Hidden] */

	TriRadius = FinishedSide/sqrt(3);

	TriPoints = [[TriRadius,0],
	[TriRadiuscos(120),TriRadiussin(120)],
	[TriRadiuscos(240),TriRadiussin(240)]
	];
	echo(str("TriPoints: ",TriPoints));

	EndPoints = [[TriRadius,0],
	[TriRadiuscos(120),TriRadiussin(120)],
	[TriRadius*cos(120),0]
	];
	echo(str("EndPoints: ",EndPoints));

	TipCutRadius = 2*(TriRadius + SeamAllowance); // circumscribing radius of tip cutter
	TipPoints = [[TipCutRadius,0],
	[TipCutRadiuscos(120),TipCutRadiussin(120)],
	[TipCutRadiuscos(240),TipCutRadiussin(240)]
	];

	HandleHeight = 1 * inch;
	HandleLength = (TemplateID + TemplateOD)/2;
	HandleThick = IntegerMultiple(3.0,ThreadWidth);
	HandleSides = 12*4;

	StringDia = 4.0;
	StringHeight = 0.6*HandleHeight;

	DentDepth = HandleThick/4;
	DentDia = 15 * DentDepth;
	DentSphereRadius = (pow(DentDepth,2) + pow(DentDia,2)/4)/(2*DentDepth);

	KnobOD = 15.0; // Triangle handle
	KnobHeight = 20.0;

	//——-

	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=HoleAdjust(FixDia)/2,h=Height,$fn=Sides);
	}


	//——-
	// Hex template

	module HexPlate() {

	difference() {
	cylinder(r=TemplateOD/2,h=TemplateThick,$fn=6);
	translate([0,0,-Protrusion])
	cylinder(r=TemplateID/2,h=(TemplateThick + 2*Protrusion),$fn=6);
	}

	for (i=[1:6/2])
	rotate(i*60)
	translate([0,0,TemplateThick/2])
	cube([HandleLength,HandleThick,TemplateThick],center=true);
	}

	module HexHandle() {

	difference() {
	rotate([90,0,0])
	scale([1,HandleHeight/(TemplateOD/2),1])
	rotate(180/HandleSides)
	cylinder(d=HandleLength,h=HandleThick,center=true,$fn=HandleSides);
	translate([0,0,-HandleHeight])
	cube([2TemplateOD,2TemplateOD,2*HandleHeight],center=true);
	translate([0,HandleThick,StringHeight])
	rotate([90,090,0])
	rotate(180/8)
	PolyCyl(StringDia,2*HandleThick,8);
	for (j=[-1,1]) {
	translate([0,j*(DentSphereRadius + HandleThick/2 – DentDepth),StringHeight])
	rotate(180/48)
	sphere(r=DentSphereRadius,$fn=48);
	}
	}

	}

	module HexTemplate() {
	HexPlate();
	HexHandle();
	}

	//——-
	// Triangle template

	module TriPlate() {

	linear_extrude(height=TemplateThick)
	intersection() {
	offset(delta=SeamAllowance) // basic cutting outline
	polygon(points=TriPoints);
	rotate(180)
	polygon(points=TipPoints);
	}
	}


	module TriTemplate() {

	union() {
	if (TriKnob)
	cylinder(d=KnobOD,h=KnobHeight,$fn=HandleSides);
	TriPlate();
	}

	}

	//——-
	// End piece template

	module EndPlate() {

	linear_extrude(height=TemplateThick)
	intersection() {
	offset(delta=SeamAllowance) // basic cutting outline
	polygon(points=EndPoints);
	rotate(180)
	polygon(points=TipPoints);
	}
	}

	module EndTemplate() {

	union() {
	if (EndKnob)
	translate([0,(TriRadius/2)*sin(30),0])
	cylinder(d=KnobOD,h=KnobHeight,$fn=HandleSides);
	EndPlate();
	}

	}



	//——-
	// Build it!

	if (Layout == "HexPlate")
	HexPlate();

	if (Layout == "HexBuild")
	HexTemplate();

	if (Layout == "TriPlate")
	TriPlate();

	if (Layout == "TriBuild")
	TriTemplate();

	if (Layout == "EndPlate")
	EndPlate();

	if (Layout == "EndBuild")
	EndTemplate();

	if (Layout == "Build") {
	translate([1.5*TriRadius,-TriRadius,0])
	rotate(180/6)
	TriTemplate();
	translate([-1.5*TriRadius,-TriRadius,0])
	rotate(180/6)
	EndTemplate();
	translate([0,TemplateOD/2,0])
	HexTemplate();
	}

view raw Quilting Hex Template.scad hosted with ❤ by GitHub

2020-08-17

Shuttles Game: Tapered Pegs

As is all too common with 3D printed replacement parts done remotely, the first Shuttles game pegs didn’t quite fit into the game board’s holes. Fortunately, living in the future means rapid prototyping and quick turnaround:

Shuttles Game pegs - tapered - solid model — Shuttles Game pegs – tapered – solid model

They’re slightly smaller, tapered toward the bottom, and take slightly less time to print.

The OpenSCAD code in the GitHub Gist now has has the tweaks.

2020-08-06

Finding & Copying Only The New Music Files

Given a collection of music files in various subdirectories, find all the mp3 files that aren’t in the target directory and copy them. The only catch: don’t use rsync, because the target directory is on a Google Pixel phone filesystem which doesn’t support various attributes required by rsync.

The solution goes like this:

cd /mnt/music/Netlabel Mixes
sudo jmtpfs /mnt/pixel -o allow_other,fsname="Pixel"
find . -name \*mp3 -execdir test ! -e  /mnt/pixel/Internal\ shared\ storage/Music/Netlabel/\{\} \; -execdir cp -v -t /mnt/pixel/Internal\ shared\ storage/Music/Netlabel/ \{\} \;
sudo umount /mnt/pixel

The trick is remembering the second execdir operation in find happens only if the first succeeds, so the cp runs when the target file doesn’t exist.

All the backslash escaping gets tedious, but it’s the least awful way to get the job done when the directories contain blanks, which is true for the default directory structure inside the Pixel.

Your choice in music will surely be different …

2020-08-05

Reinforced QD Propane Adapter Tool

Having just emptied a propane tank while making bacon, I couldn’t find any of the wrench adapters I made to remove the QD adapter from the tank’s POL fitting. With memory of the broken garden valve wrench still fresh, I tweaked the solid model to include a trio of 1 mm music wire reinforcements:

Propane QD Adapter Tool - reinforced - Slic3r — Propane QD Adapter Tool – reinforced – Slic3r

Holes that small require clearing with a 1 mm drill, after which ramming the wires in place poses no problem:

Reinforced QD Adapter Tool - inserting wire — Reinforced QD Adapter Tool – inserting wire

Except for the one that got away:

Reinforced QD Adapter Tool - errant wire — Reinforced QD Adapter Tool – errant wire

The music wire came from a coil and each snippet required gentle straightening; perhaps that one wasn’t sufficiently bar-straight.

Anyhow, I printed two tools for that very reason:

Reinforced QD Adapter Tool - side view — Reinforced QD Adapter Tool – side view

They’re now where I can’t miss ’em the next time I need them, although that’s not where the previous ones reside.

The OpenSCAD source code as a GitHub Gist:

	// Propane tank QD connector adapter tool
	// Ed Nisley KE4ZNU November 2012
	// 2018-04-08 toss MCAD includes overboard
	// 2020-07-27 add reinforcing rods

	//- Extrusion parameters must match reality!
	// Print with about half a dozen perimeter threads and 50% infill

	ThreadThick = 0.25;
	ThreadWidth = 2.0 * ThreadThick;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	//———————-
	// Dimensions

	WrenchSize = (5/8) * inch; // across the flats
	WrenchThick = 10;

	NoseDia = 8.6;
	NoseLength = 9.0;

	LockDia = 12.5;
	LockRingLength = 1.0;
	LockTaperLength = 1.5;

	TriDia = 15.1;
	TriWide = 12.2; // from OD across center to triangle side
	TriOffset = TriWide – TriDia/2; // from center to triangle side
	TriLength = 9.8;

	NeckDia = TriDia;
	NeckLength = 4.0;

	RebarOD = 1.0; // music wire pin 1 mm = 39 mil
	RebarLength = WrenchThick + NeckLength + TriLength;

	//———————-
	// 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);
	}


	//——————-
	// Build it…

	$fn = 4*6;

	union() {

	translate([0,0,(WrenchThick + NeckLength + TriLength – LockTaperLength – LockRingLength + Protrusion)])
	cylinder(r1=NoseDia/2,r2=LockDia/2,h=LockTaperLength);

	translate([0,0,(WrenchThick + NeckLength + TriLength – LockRingLength)])
	cylinder(r=LockDia/2,h=LockRingLength);

	difference() {
	union() {

	translate([0,0,WrenchThick/2])
	cube([WrenchSize,WrenchSize,WrenchThick],center=true);

	cylinder(r=TriDia/2,h=(WrenchThick + NeckLength +TriLength));

	cylinder(r=NoseDia/2,h=(WrenchThick + NeckLength + TriLength + NoseLength));
	}

	for (a=[-1:1]) {
	rotate(a*120)
	translate([(TriOffset + WrenchSize/2),0,(WrenchThick + NeckLength + TriLength/2 + Protrusion/2)])
	cube([WrenchSize,WrenchSize,(TriLength + Protrusion)],center=true);
	}

	for (a=[-1:1]) {
	rotate(a*120 + 60)
	translate([NoseDia/2,0,-Protrusion])
	PolyCyl(RebarOD,RebarLength,6);
	}

	}
	}

view raw Propane QD Adapter Tool.scad hosted with ❤ by GitHub

2020-07-31

NPN RGB Astable Multivibrator Timing Adjustment

Back in the beginning of July, I replaced the NP-BX1 battery in the RGB Piranha astable multivibrator with a 18650 lithium cell and a USB charge controller, then watched it blink for the next two weeks on the first charge:

Astable - 10 11 12 uF tweak - 027 — Astable – 10 11 12 uF tweak – 027

However, the blinks looked … odd and some poking around with a Tek current probe showed the red and blue astables had locked together, so they blinked in quick succession. Alas, I don’t have a scope shot to prove it.

I built all three astables with the same parts, figuring the normal tolerance of electrolytic caps would make the astables run at slightly different rates, which they did at first.

This being a prototype, I just soldered a 1 µF cap onto the blue channel’s existing 10 µF cap:

Astable - 11 uF cap - detail — Astable – 11 uF cap – detail

You can barely make out the top of the additional 2.2 µF cap on the red channel, through the maze of components; now, they definitely have different periods.

Aaaand the scope shot to prove it:

Astable NPN - 10 11 12 uF tweak - 10 mA-div — Astable NPN – 10 11 12 uF tweak – 10 mA-div

The bottom trace shows the battery current at 10 mA/div. The first pulse, over on the left, has the red and blue LEDs firing in quick succession with some overlap, but they separate cleanly for their next pulses.

You don’t want to build a battery-powered astable from NPN transistors, because the 8 mA current between blinks is murderously high. In round numbers, each of the three LEDs blinks twice a second for 30 ms at 20 mA, so they average 3.6 mA, less than half the current required to keep the astables running between blinks. Over the course of 14 days, the circuit drew 11.6 mA × 336 hr = 3900 mA·h until the protection circuit shut it down.

The lead photo shows a harvested 18650 cell, but I started with a known-good Samsung 18650 cell rated at 2600 mA·h at a 0.2C = 520 mA rate to 2.75 V. It’s comforting to see more energy trickling out at a 0.005C rate!

I must conjure a holder with contacts for an 18650 cell, support for a trio of 2N7000 MOSFET astables, and some kind of weird spider with the RGB Piranha LED on the top. Even a harvested 18650 cell should last a couple of months with a much longer blink period (500 ms is much too fast), less LED current (this one is shatteringly bright), and a lower average current.

And, yeah, I’ve been misspelling “Piranha” for a while.

2020-07-29

Pan Lid Handle Quieting

A surprisingly heavy stainless steel pan lid from the local ReStore has only one fault: when placed upside-down on the counter while we’re tending the pan contents, it will rock back and forth for nearly a minute. The lid has a rubberized insert for finger protection:

Pan lid - original handle — Pan lid – original handle

However, the inserts cover only the side of the handle, so the metal arch rests on the counter. Setting it up in the shop let me scuff up the handle contact points:

Pan lid - contact point — Pan lid – contact point

Then some Dremel grinding wheel work recessed the handle just barely below the inserts and changed the arch enough to keep it off the counter:

Pan lid - recessed handle crest — Pan lid – recessed handle crest

The lid now stops rocking after a few seconds and is much quieter while doing so. It may require a bit more grinding, but it’s much better after this small intervention.

2020-07-26