Category: Electronics Workbench

Electrical & Electronic gadgets

Alpha Geek Clock: Radome Update

There being nothing like a new problem to take one’s mind off all one’s old problems:

C-Max CMMR-60 WWVB receiver - D cell display holder — C-Max CMMR-60 WWVB receiver – D cell display holder

It’s a variation on the camera battery and AA alkaline holders for various blinky LEDs:

Astable Multivibrator - D cell WWVB — Astable Multivibrator – D cell WWVB

The little flag holding the C-Max CMMR-60 receiver PCB gets glued to the copper upright to keep it from swiveling in the breeze.

The conical caps on the ferrite bar antenna are glued to the uprights and the antenna, in the expectation this is a one-off build-only project.

Rather than buy specialized D-cell contacts, I used 18650 lithium cell contacts and conjured the bridge by soldering two together:

D cell bridge contact from 18650 contacts

It sits on the windowsill, blinks quietly in the dark, and flickers invisibly during the daytime.

Those D cells came from the same batch that powered the previous version for the last five years, so they probably won’t last that long, even with a Nov 2024 date code.

C-Max is apparently out of the WWVB biz, but you can get a similar Canaduino AM WWVB receiver.

The far more complex EverSet ES100-MOD WWVB receiver requires a microcontroller with an I²C interface and very careful power management.

The OpenSCAD source code as a GitHub Gist:

	// Astable Multivibrator
	// Holder for Alkaline cells
	// Ed Nisley KE4ZNU August 2020
	// 2020-09 add LED radome
	// 2020-11 add radome trim
	// 2021-11 D cells and WWVB receiver

	/* [Layout options] */

	Layout = "Build"; // [Build,Show,Lid,Spider,AntCap,RecFlag]

	CellName = "AA"; // [AA, D]

	Struts = -1; // [0:None, -1:Dual, 1:Quad]

	WWVB = true;

	/* [Hidden] */

	NumCells = 2; // [2]

	// Extrusion parameters

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	//- Basic dimensions

	WallThick = IntegerMultiple(3.0,ThreadWidth);
	CornerRadius = WallThick/2;

	FloorThick = IntegerMultiple(3.0,ThreadThick);

	TopThick = IntegerMultiple(2.0,ThreadThick);

	WireOD = 1.5; // battery & LED wiring
	WireOC = 8.0; // hole spacing in lid

	Gap = 5.0;

	// Cylindrical cell sizes
	// https://en.wikipedia.org/wiki/List_of_battery_sizes#Cylindrical_batteries

	CELL_NAME = 0;
	CELL_OD = 1;
	CELL_OAL = 2;

	// FIXME search() needs special-casing to properly find AAA and AAAA
	// Which is why CellName is limited to AA

	CellData = [
	["AAAA",8.3,42.5],
	["AAA",10.5,44.5],
	["AA",14.5,50.5],
	["C",26.2,50],
	["D",34.2,61.5],
	["A23",10.3,28.5],
	["CR123A",17.0,34.5],
	["18650",18.8,65.2], // bare 18650 with button end
	["18650Prot",19.0,70.0], // protected 18650 = 19670 plus a bit
	];

	CellIndex = search([CellName],CellData,1,0)[0];
	echo(str("Cell index: ",CellIndex," = ",CellData[CellIndex][CELL_NAME]));

	//- Contact dimensions

	CONTACT_NAME = 0;
	CONTACT_WIDE = 1;
	CONTACT_HIGH = 2;
	CONTACT_THICK = 3; // plate thickness
	CONTACT_TIP = 4; // tip to rear face
	CONTACT_TAB = 5; // solder tab width

	ContactData = [
	["AA+",12.2,12.2,0.3,1.7,3.5], // pos bump
	["AA-",12.2,12.2,0.3,5.0,3.5], // half-compressed neg spring
	["AA+-",28.2,12.2,0.3,5.0,0], // pos-neg bridge

	["D+",18.5,16.0,0.3,2.8,5.5],
	["D-",18.5,16.0,0.3,6.0,5.5],
	["D+-",50.0,19.0,0.3,7.0,0], // solder +/- tabs together

	["Li+",18.5,16.0,0.3,2.8,5.5],
	["Li-",18.5,16.0,0.3,6.0,5.5],
	];

	function ConDat(name,dim) = ContactData[search([name],ContactData,1,0)[0]][dim];

	ContactRecess = 2*ConDat(str(CellName,"+"),CONTACT_THICK);
	ContactOC = CellData[CellIndex][CELL_OD];

	WireBay = 6.0; // room for wiring to contacts

	//- Wire struts

	StrutDia = 1.6; // AWG 14 = 1.6 mm
	StrutSides = 3*4;

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

	StrutBase = [StrutDia,StrutDia + 25ThreadWidth, // ID = wire, OD = buildable
	FloorThick + CellData[CellIndex][CELL_OD]]; // LENGTH = base is flush with cell top

	//- Holder dimensions

	BatterySize = [CellData[CellIndex][CELL_OAL] + // cell
	ConDat(str(CellName,"+"),CONTACT_TIP) + // pos contact
	ConDat(str(CellName,"-"),CONTACT_TIP) – // neg contact
	2*ContactRecess, // sink into wall
	NumCells*CellData[CellIndex][CELL_OD],
	CellData[CellIndex][CELL_OD]
	];

	echo(str("Battery space: ",BatterySize));

	CaseSize = [3*WallThick + // end walls + wiring partition
	BatterySize.x + // cell
	WireBay, // wiring bay
	2*WallThick + BatterySize.y,
	FloorThick + BatterySize.z
	];
	echo(str("CaseSize: ",CaseSize));

	BatteryOffset = (CaseSize.x – (2*WallThick +
	CellData[CellIndex][CELL_OAL] +
	ConDat(str(CellName,"-"),CONTACT_TIP))
	) /2 ;

	ThumbRadius = 0.75 * CaseSize.z;


	StrutOC = [IntegerLessMultiple(CaseSize.x – 2CornerRadius -2StrutBase[OD],5.0),
	IntegerMultiple(CaseSize.y + StrutBase[OD],5.0)];

	StrutAngle = atan(StrutOC.y/StrutOC.x);

	echo(str("Strut OC: ",StrutOC));

	LidSize = [2*WallThick + WireBay + ConDat(str(CellName,"+"),CONTACT_THICK), CaseSize.y, FloorThick/2];

	LidScrew = [2.0,3.8,7.0]; // M2 pan head screw (LENGTH = threaded)
	LidScrewOC = CaseSize.y/2 – CornerRadius – LidScrew[OD]; // allow space around screw head

	//- Piranha LEDs

	PiranhaBody = [8.0,8.0,8.0]; // Z = heatsink fins + plastic body + lens

	PiranhaPin = 0.0; // trimmed pin length beyond heatsink
	PiranhaPinsOC = [5.0,5.0]; // pin XY distance

	PiranhaRecess = PiranhaBody.z + PiranhaPin/2; // minimum LED recess depth

	BallOD = 40.0; // radome sphere
	BallSides = 434; // nice smoothness

	PillarOD = norm([PiranhaBody.x,PiranhaBody.y]) + 2*WallThick;

	BallChordM = BallOD/2 – sqrt(pow(BallOD/2,2) – (pow(PillarOD,2))/4);
	echo(str("Ball chord depth: ",BallChordM));

	RadomePillar = [norm([PiranhaBody.x,PiranhaBody.y]), // ID = LED diagonal
	PillarOD,
	FloorThick + PiranhaRecess + BallChordM]; // height to top of ball chord
	echo(str("Pillar: ",RadomePillar));

	RadomeBar = [StrutBase[OD]*cos(180/StrutSides),StrutOC.y,StrutBase[OD]/2];

	Tape = [RadomePillar[ID],16.0,1.0]; // sticky tape disk, OD to match hole punch

	//- WWVB receiver hardware

	Antenna = [10.0 + 0.5,14.0,60.0 + 2.0]; // ferrite antenna bar with clearance

	AntCapSize = [Antenna[ID] + 1.0,Antenna[OD],5.0]; // LENGTH=insertion

	RecPCB = [24.0,16.0,5.0];

	//———————-
	// 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);
	}

	// Spider for single LED atop struts, with the ball

	module DualSpider() {

	difference() {
	union() {
	for (j=[-1,1]) {
	for (k=[-1,1])
	translate([0,jStrutOC.y/2,kRadomeBar.z])
	rotate(180/StrutSides)
	sphere(d=StrutBase[OD]/cos(180/StrutSides),$fn=StrutSides);
	translate([0,j*StrutOC.y/2,0])
	rotate(180/StrutSides)
	cylinder(d=StrutBase[OD],h=2*RadomeBar.z,center=true,$fn=StrutSides);
	}

	cube(RadomeBar,center=true); // connecting bar

	cylinder(d=RadomePillar[OD],h=RadomePillar[LENGTH],$fn=BallSides);

	translate([0,0,-RadomeBar.z/2])
	cylinder(d1=0.9*RadomePillar[OD],d2=RadomePillar[OD],h=RadomeBar.z/2,$fn=BallSides);
	}

	for (j=[-1,1]) // strut wires
	translate([0,jStrutOC.y/2,-3StrutBase[OD]/2])
	rotate(180/StrutSides)
	PolyCyl(StrutBase[ID],2*StrutBase[OD],StrutSides);

	for (k=[-1,1]) // LED wiring through bar
	translate([0,k(StrutOC.x/2 – 2RadomeBar.x),-RadomeBar.z])
	rotate(180/6)
	PolyCyl(StrutBase[ID],2*RadomeBar.z,6);

	translate([0,0,BallOD/2 + RadomePillar[LENGTH] – BallChordM]) // ball inset
	sphere(d=BallOD);

	translate([0,0,BallOD/2 + RadomePillar[LENGTH] – BallChordM – Tape[LENGTH]/2]) // tape inset
	intersection() {
	sphere(d=BallOD);
	cylinder(d=Tape[OD],h=2*BallOD,center=true);
	}

	translate([0,0,RadomePillar.z – PiranhaRecess + RadomePillar.z/2]) // LED inset
	cube(PiranhaBody + [HoleWindage,HoleWindage,RadomePillar.z],center=true); // XY clearance

	translate([0,0,StrutBase[OD]/4 + WireOD/2 + 0*Protrusion]) // wire channels
	cube([WireOD,RadomePillar[OD] + 2*WallThick,WireOD],center=true);

	}
	}

	//– WWVB antenna support cap

	module AntennaBar() {
	rotate([90,0,0])
	union() {
	cylinder(d=Antenna[ID],h=Antenna[LENGTH],$fn=BallSides,center=true);
	cylinder(d=2Antenna[OD],h=Antenna[LENGTH] – 2AntCapSize[LENGTH],$fn=BallSides,center=true);
	}
	}

	module AntennaCap() {
	rotate([90,0,0])
	intersection() {
	translate([0,-Antenna[LENGTH]/2 + AntCapSize[LENGTH],0])
	difference() {
	hull() {
	rotate([90,0,0])
	cylinder(d=AntCapSize[OD],h=Antenna[LENGTH],$fn=BallSides,center=true);
	for (j=[-1,1])
	translate([0,j*StrutOC.y/2,0])
	rotate(180/StrutSides)
	cylinder(d=StrutBase[OD],h=1*StrutBase[OD],$fn=StrutSides,center=true);
	}
	for (j=[-1,1])
	translate([0,j*StrutOC.y/2,-Antenna[OD]/2])
	rotate(180/StrutSides)
	PolyCyl(StrutBase[ID],Antenna[OD],StrutSides);
	AntennaBar();
	}
	rotate([-90,0,0])
	cylinder(d=Antenna[OD],h=Antenna[LENGTH],center=false);
	}
	}


	//– WWVB PCB support flag

	module RecFlag() {

	difference() {
	hull() {
	rotate(180/StrutSides)
	cylinder(d=StrutBase[OD],h=RecPCB.x,$fn=StrutSides);
	translate([0,RecPCB.y,0])
	rotate(180/StrutSides)
	cylinder(d=StrutBase[OD],h=RecPCB.x,$fn=StrutSides);
	}
	translate([0,0,-Protrusion])
	rotate(180/StrutSides)
	PolyCyl(StrutBase[ID],2*RecPCB.x,StrutSides);
	translate([0,StrutBase[OD]/2,-Protrusion])
	cube([StrutBase[OD],RecPCB.y,2*RecPCB.x],center=false);
	}

	}

	//– Overall case with origin at battery center

	module Case() {

	union() {

	difference() {
	union() {
	hull()
	for (i=[-1,1], j=[-1,1])
	translate([i*(CaseSize.x/2 – CornerRadius),
	j*(CaseSize.y/2 – CornerRadius),
	0])
	cylinder(r=CornerRadius/cos(180/8),h=CaseSize.z,$fn=8); // cos() fixes undersize spheres!

	if (Struts)
	for (i = (Struts == 1) ? [-1,1] : -1) { // strut bases
	hull()
	for (j=[-1,1])
	translate([iStrutOC.x/2,jStrutOC.y/2,0])
	rotate(180/StrutSides)
	cylinder(d=StrutBase[OD],h=StrutBase[LENGTH],$fn=StrutSides);

	translate([i*StrutOC.x/2,0,StrutBase[LENGTH]/2])
	cube([2*StrutBase[OD],StrutOC.y,StrutBase[LENGTH]],center=true); // blocks for fairing

	for (j=[-1,1]) // hemisphere caps
	translate([i*StrutOC.x/2,
	j*StrutOC.y/2,
	StrutBase[LENGTH]])
	rotate(180/StrutSides)
	sphere(d=StrutBase[OD]/cos(180/StrutSides),$fn=StrutSides);

	}
	}

	translate([BatteryOffset,0,BatterySize.z/2 + FloorThick]) // cells
	cube(BatterySize + [0,0,Protrusion],center=true);

	translate([BatterySize.x/2 + BatteryOffset + ContactRecess/2 – Protrusion/2, // contacts
	0,
	BatterySize.z/2 + FloorThick])
	cube([ContactRecess + Protrusion,
	ConDat(str(CellName,"+-"),CONTACT_WIDE),
	ConDat(str(CellName,"+-"),CONTACT_HIGH)
	],center=true);

	translate([-(BatterySize.x/2 – BatteryOffset + ContactRecess/2 – Protrusion/2),
	ContactOC/2,
	BatterySize.z/2 + FloorThick])
	cube([ContactRecess + Protrusion,
	ConDat(str(CellName,"+"),CONTACT_WIDE),
	ConDat(str(CellName,"+"),CONTACT_HIGH)
	],center=true);

	translate([-(BatterySize.x/2 – BatteryOffset + ContactRecess/2 – Protrusion/2),
	-ContactOC/2,
	BatterySize.z/2 + FloorThick])
	cube([ContactRecess + Protrusion,
	ConDat(str(CellName,"-"),CONTACT_WIDE),
	ConDat(str(CellName,"-"),CONTACT_HIGH)
	],center=true);

	translate([-CaseSize.x/2 + WireBay/2 + WallThick, // wire bay with screw bosses
	0,
	BatterySize.z/2 + FloorThick + Protrusion/2])
	cube([WireBay,
	2LidScrewOC – LidScrew[ID] – 24*ThreadWidth,
	BatterySize.z + Protrusion
	],center=true);

	for (j=[-1,1]) // screw holes
	translate([-CaseSize.x/2 + WireBay/2 + WallThick,
	j*LidScrewOC,
	CaseSize.z – LidScrew[LENGTH] + Protrusion])
	PolyCyl(LidScrew[ID],LidScrew[LENGTH],6);


	for (j=[-1,1])
	translate([-(BatterySize.x/2 – BatteryOffset + WallThick/2), // contact tabs
	j*ContactOC/2,
	BatterySize.z + FloorThick – Protrusion])
	cube([2*WallThick,
	ConDat(str(CellName,"+"),CONTACT_TAB),
	(BatterySize.z – ConDat(str(CellName,"+"),CONTACT_HIGH))
	],center=true);

	if (false)
	translate([0,0,CaseSize.z]) // finger cutout
	rotate([90,00,0])
	cylinder(r=ThumbRadius,h=2*CaseSize.y,center=true,$fn=22);

	if (Struts)
	for (i2 = (Struts == 1) ? [-1,1] : -1) { // strut wire holes and fairing
	for (j=[-1,1])
	translate([i2StrutOC.x/2,jStrutOC.y/2,FloorThick])
	rotate(180/StrutSides)
	PolyCyl(StrutBase[ID],2*StrutBase[LENGTH],StrutSides);

	for (i=[-1,1], j=[-1,1]) // fairing cutaways
	translate([iStrutBase[OD] + (i2StrutOC.x/2),
	j*StrutOC.y/2,
	-Protrusion])
	rotate(180/StrutSides)
	PolyCyl(StrutBase[OD],StrutBase[LENGTH] + 2*Protrusion,StrutSides);
	}

	translate([0,0,ThreadThick – Protrusion]) // recess around name
	cube([51.0,15,2*ThreadThick],center=true);

	}

	linear_extrude(height=2*ThreadThick + Protrusion,convexity=10) {
	translate([0,-3.5,0])
	mirror([0,1,0])
	text(text="softsolder",size=6,spacing=1.20,font="Arial:style:Bold",halign="center",valign="center");
	translate([0,3.5,0])
	mirror([0,1,0])
	text(text=".com",size=6,spacing=1.20,font="Arial:style:Bold",halign="center",valign="center");
	}
	}
	}


	module Lid() {

	difference() {
	hull()
	for (i=[-1,1], j=[-1,1], k=[-1,1])
	translate([i*(LidSize.x/2 – CornerRadius),
	j*(LidSize.y/2 – CornerRadius),
	k*(LidSize.z – CornerRadius)]) // double thickness for flat bottom
	sphere(r=CornerRadius/cos(180/8),$fn=8);

	translate([0,0,-LidSize.z]) // remove bottom
	cube([(LidSize.x + 2Protrusion),(LidSize.y + 2Protrusion),2*LidSize.z],center=true);

	for (j=[-1,1]) // wire holes
	translate([0,j*WireOC/2,-Protrusion])
	PolyCyl(WireOD,2*LidSize.z,6);

	for (j=[-1,1])
	translate([0,j*LidScrewOC,-Protrusion])
	PolyCyl(LidScrew[ID],2*LidSize.z,6);

	}
	}


	//——————-
	// Show & build stuff

	if (Layout == "Case")
	Case();

	if (Layout == "Lid")
	Lid();

	if (Layout == "AntCap")
	AntennaCap();

	if (Layout == "RecFlag")
	RecFlag();

	if (Layout == "Spider")
	if (Struts == -1)
	DualSpider();
	else
	cube(10,center=true);

	if (Layout == "Build") {
	rotate(90)
	Case();
	translate([0,-(CaseSize.x/2 + LidSize.x/2 + Gap),0])
	rotate(90)
	Lid();
	if (Struts == -1) {
	difference() {
	union() {
	translate([CaseSize.x/2 + RadomePillar[OD],0,0])
	DualSpider();
	translate([-(CaseSize.x/2 + RadomePillar[OD]),0,0])
	rotate([180,0,0])
	DualSpider();
	}
	translate([0,0,-2*CaseSize.z])
	rotate(90)
	cube(4*CaseSize,center=true);
	}
	}
	if (WWVB) {
	for (i=[-1,1])
	translate([i*(Antenna[LENGTH]/2 – AntCapSize[LENGTH]),CaseSize.x/2 + Antenna[OD],0])
	AntennaCap();
	translate([0,CaseSize.x/2 + Antenna[OD],0])
	RecFlag();
	}
	}

	if (Layout == "Show") {
	Case();
	for (j=[-1,1])
	color("Brown",0.3)
	translate([-StrutOC.x/2,j*StrutOC.y/2,Protrusion])
	cylinder(d=StrutDia[ID],h=3*CaseSize.z,$fn=StrutSides);
	translate([-(CaseSize.x/2 – LidSize.x/2),0,(CaseSize.z + Gap)])
	Lid();
	if (Struts == -1)
	translate([-StrutOC.x/2,0,3*CaseSize.z])
	DualSpider();
	if (WWVB) {
	for (j=[-1,1])
	translate([-StrutOC.x/2,,j(Antenna[LENGTH]/2 – AntCapSize[LENGTH]),1.5CaseSize.z])
	rotate([-j*90,0,0])
	AntennaCap();
	translate([-StrutOC.x/2,,-(StrutOC.y/2),2*CaseSize.z])
	RecFlag();
	}
	}

view raw Astable Multivibrator – Alkaline Batteries.scad hosted with ❤ by GitHub

2021-11-17

LED-ified Halogen Desk Lamp: DC LED Driver

Feeding half-wave rectified 12 V AC into the 4 W LED lamp I hung on the end of the halogen desk lamp worked at human scale, but produced dark bars across images made with my Pixel phones. Having solved that problem for the LED lighting on Mary’s sewing machines, I replaced the OEM transformer with a 12 VDC power supply:

LED Desk Lamp – Driver installed

The steel lump inside the base is the OEM weight that, in addition to two pounds of transformer, kept the whole affair from toppling over.

The transformer inside the DC supply weighs basically nothing:

LED Desk Lamp – Driver PCB

The original 12 VAC transformer powered a 50 W halogen bulb and loafed along at 14.7 VAC (yes, RMS) into the 4 W LED. The light is somewhat dimmer at 12 VDC, but not enough to worry about.

Aaaaand the photo bars are gone!

2021-11-16
Alpha Geek Clock: Battery Refresh

A pair of D cells can power an obsolete / out of production C-Max CMMR-60 WWVB receiver for about five years and, having the plastic pieces for a blinkie at hand, junking the faded case in favor of a test lashup seemed appropriate:

C-Max CMMR-60 WWVB receiver – AA alkaline test setup

Given the fragility of that ferrite bar, I should conjure a wide D-cell base, a bar holder to cover the ends, and a PCB mount of some sort.

The receiver data pin drives the red LED of an RGB piranha through a 2.2 kΩ SMD resistor, so it’s visible in a dim room. Given that the thing flickers constantly during WWVB’s poor-reception daylight hours, reducing the LED current counts for almost everything.

The antenna has a cap under that heatshrink tubing, which called for a resonance check:

C-Max CMMR-60 WWVB receiver – antenna peaking – driver coil

The blue dingus is an RF sniffer driven three orders of magnitude below its frequency spec:

C-Max CMMR-60 WWVB receiver – antenna peaking – function generator

The antenna response peaks where you’d expect:

C-Max CMMR-60 WWVB receiver – antenna peaking – scope

Given the broad peak and typical tolerances, it’s spot on.

2021-11-15
Alpatronix iPhone XS Max Wireless Charging Case: Battery Capacity

Mostly because I have the technology, here’s a battery rundown test for the (guts of the) Alpatronix iPhone case:

Alpatronix iPhone XS case – battery test setup

Bypassing the entire battery controller doesn’t tell you when it thinks the lights should go out, but does give an indication of the raw battery capacity:

Alpatronix iPhoneXS Charger – 2021-11-06

Multiplying the nominal 3.7 V by the nominal 5 A·hr capacity says it should have a nominal 18.5 W·hr capacity at some unrealistically low discharge rate. Given that I found it at the end of the driveway with no provenance, I didn’t expect much.

To my utter astonishment, it delivered 17 W·hr at 500 mA!

It really ought to be good for something …

2021-11-12
Shopvac QSP Motor Commutator Cleaning

The Greatest Shopvac emitted an intense smell of electrical death while inhaling fuzzballs from the Basement Shop stairs, prompting me to tear it down. For the record, it’s a Genuine Shop·Vac QSP 10 (Quiet Super Power):

Shopvac QSP – label

Removing the handle and upper plate reveals a slab of (presumably) sound-deadening foam over the motor cooling fan. As far as I can tell, the last job this vacuum had before the previous owner discarded it was inhaling drywall dust without a filter:

Shopvac QSP – upper sound baffle

Flipping the motor assembly over and removing the bottom plate revealed a pair of equally solidified foam slabs baffling the main exhaust path:

Shopvac QSP – sound baffle foam

They eventually became Clean Enough™ after protracted rinsing, so maybe the thing now runs as quietly as the name would lead you to believe, if you believed in names.

Disconnecting and extracting the motor revealed the razor-sharp impeller disk. A shop rag prevents lacerations while torquing off the nut holding it to the shaft:

Shopvac QSP – impeller nut

Rust on the washer below the impeller, along with the layer of caked white cement, suggested water accompanied the drywall dust:

Shopvac QSP – impeller washer

Gentle suasion from the Designated Prydriver eventually eased the washer off the shaft and freed the motor:

Shopvac QSP – motor brush layout

It’s an old-school series-wound brushed universal motor. The plastic plate in the middle of the picture has a helical spring pressing the carbon brush against the commutator:

Shopvac QSP – motor brush detail

The rotor turned … reluctantly with the brushes in place and spun freely without them, suggesting the horrible smell of electrical death came from arcing across the gunk accumulated on the commutator:

Shopvac QSP – commutator as found

Many iterations of diligent scrubbing with denatured alcohol on cotton swabs and old t-shirt snippets got rid of the crud, although that commutator will never look all shiny-clean again:

Shopvac QSP – commutator cleaned

At least the brushes aren’t glued to it!

Reassembly is in reverse order, although I took the liberty of splicing a few inches of wire into the switch leads, because I’m not working under factory conditions with all the proper assembly fixtures:

Shopvac QSP – extended wires

The motor passed the smoke test and no longer smells like death, so it’s at least as good as it ever was.

It may run quieter with clean foam baffles, but I still turn off my power ears or don hearing protection when I fire up any shop vacuum.

2021-11-11
Wireless Numeric Keypad vs. AmazonBasics AAA Alkaline

One of the streaming media players behaved funny, which always results in a numeric keypad battery replacement. This AmazonBasics AAA alkaline was down to about 0.5 V and long past its best-used-by date:

Numeric keypad – 5 year Amazon AAA Alkaline

Nigh onto six years isn’t bad, particularly as it hasn’t leaked electrolyte all over the negative terminal.

Suggestions that Amazon monitors their Marketplace sellers to figure out what’s profitable, then promote a Good Enough house brand product to kill off the competition, seem to describe the situation just about perfectly.

2021-11-10
Alpatronix iPhone XS Max Wireless Charging Case Teardown

A battered Alpatronix iPhone XS Max wireless charging case emerged from the ground cover at the end of the driveway:

Alpatronix iPhone XS case – overview

The iPhone was nowhere to be found, so harvesting its organs seemed appropriate:

Alpatronix iPhone XS case – opened

I assume the four steel disks aligned the coil with the wireless charger.

A few hours of steady tension relieved enough of the sticky tape to release the battery:

Alpatronix iPhone XS case – battery removal

Although its bag now sports a few wrinkles:

Alpatronix iPhone XS case – battery adhesion

The alert reader will note the outside of case proudly proclaimed “Capacity: 5000 mAh” while the underside of the battery says “4920 mAh”, but that’s surely close enough for consumer electronics these days.

The battery charges through either the Qi coil or a (mercifully standard Micro-B) USB jack and everything seems to work.

Not sure what I’ll do with a bare lithium cell and its charger, but they ought to come in handy for something around here.

2021-11-08