The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Machine Shop

Mechanical widgetry

Amazon EK3211 Kitchen Scale

An unfortunate incident put enough water inside our kitchen scale to, ummm, render it inoperative. After a day of drying proved unavailing, I had nothing to lose by disassembling it.

The central label on the back conceals two screws holding the platform to the aluminum beam:

Amazon EK3211 Scale – platform underside

The metal plate twist-locks into the plastic platform. The hot-melt glue holding it in position suggests my construction techniques aren’t all that far off the mark.

The beam cantilevers from a metal structure spreading the load across the plastic base:

Amazon EK3211 Scale – interior overview

These are “after” pictures. Suffice it to say the interior was wet, including water droplets between the LCD panel and its plastic cover. Everything came apart easily, including the LCD with its attached zebra connector, and dried out thoroughly over the next day; I parked the panel atop my monitor for some gentle heating.

After reassembly, it still didn’t work, which turned out to be due to both wires from the battery snapping off at their PCB solder joints. I didn’t think I’d handled it that roughly, but ya never know.

With the wires soldered in place, the scale lit right up again:

Amazon EK3211 Scale – display PCB switches

The display flashed CAL at one point during the proceedings, although the rather thin manual had nothing to say about recalibration and the PCB didn’t have any obvious test points / jumpers / labels to that effect.

Two days of relentless spelunking produced my test weights:

Amazon EK3211 Scale – test weights

Given the provenance of those weights, a 0.2% error might not be the scale’s fault, even if it cost barely 10 bucks.

2017-04-06
Bosch Laser Rangefinder Corrosion

A few days after using my Bosch GLR225 Laser Rangefinder, it wouldn’t light up.

This came as no surprise:

Bosch GLR225 battery contact – corrosion

Some vinegar, a bit of scrubbing, some rinsing, and it’s all good:

Bosch GLR225 battery contact – cleaned

The OEM batteries seem to have survived nigh onto four years, so I guess I can’t complain.

Mutter & similar remarks.

2017-04-05
Kensington Expert Mouse Cable Replacement

My posts about troubles with the Kensington Expert Mouse scroll ring remain disturbingly popular. My most recent warranty replacement has been running fine for several years, so I suspect they had a bad lot of IR detectors go their production line and into the field.

In any event, a recent email asked about where to get the little connector inside the mouse to replace a worn-out USB cable:

Kensington Expert Mouse – internal USB connector

Maybe you’d be lucky enough to find an identical connector inside an old mouse in a junk box, but that’s not the way to bet.

Given that you need not only the proper plastic shell, but also the pins and the crimper for a proper repair, I suggested just chopping the wires an inch from the connector and splicing the new cable onto the wires.

Not an elegant solution, but it works for me …

2017-04-03
AADE LC Meter: AT26 Crystal Capacitance Fixture

Crystals (or resonators) in AT26 packages have vanishingly small capacitances, so I conjured a little fixture for my AADE L/C Meter IIB (*) that holds them securely under little fingers snipped from an EMI shield:

AT26 crystal capacitance fixture – Cpar detail

The finger on the right sits atop a snippet of rectangular brass tube so it need not bend so far.

The base is a snippet of double-sided PCB with copper tape soldered around the edges. I drilled the holes slightly oversize and soldered copper tape there, giving the top foil a direct connection to the terminals. The raggedy slot looks like it came from a hacksaw; no false advertising there.

The meter reports 6.5 pF of stray capacitance and nulls it to zero as usual. Without the fixture, it shows 2.5 pF.

With the crystal in that position, the meter measures Cpar, the parasitic capacitance from both terminals to the can, which should be (roughly) twice the capacitance from either terminal to the can.

Two more clips measure C0, the plate-to-plate capacitance:

AT26 crystal capacitance fixture – C0 detail

The meter drive is about 200 mV at 700 kHz, far away from resonance. Assuming the resonator’s effective series resistance is 25 kΩ (tuning forks aren’t crystals!), it’s dissipating 1.5 µW (and less as the ESR goes up). That may be slightly hot for some resonators, but it’s surely survivable.

Some preliminary data on five 32.768 kHz crystals shows Cpar = 0.4 pF and C0 = 0.9 pF. I don’t trust those numbers very much, but they’re reproducible within 0.1-ish pF.

(*) Almost All Digital Electronics and its website vanished after the owner died; the meter continues to work fine. The cheap knockoffs flooding eBay and Amazon may get you close to the goal.

2017-03-27
Quartz Tuning Fork Resonator Teardown

Thinking of a 60 kHz crystal filter front end for the WWVB receiver brought a little bag of 32.768 kHz crystals to the surface; I figured I could use them as crash test dummies while a bag of 60 kHz crystals travels around the planet. Come to find out they don’t behave quite like crystals and a bit of investigation shows the little cans contain tuning fork resonators, not crystal slabs.

I had to see that, so I grabbed the base of one in a pin vise:

Quartz resonator – pin vise

I don’t know the part number for those resonators, but it’s something like AT26, where the “26” means a cylindrical can 2 mm OD and 6 mm long, more or less.

Notching the can at the chuck with a triangular file, then wiggling the can with needle-nose pliers, eventually broke it off:

Quartz resonator – A side

The other side:

Quartz resonator – B side

A look through the microscope show they’re transparent, with laser trim scars on the ends:

Quartz resonator – detail

The “holes” are unplated quartz areas, clear as the finest glass.

Not what I was expecting to see, at all!

2017-03-24

Vacuum Tube Lights: Duodecar Rebuild

You’ll recall the LED atop the 21HB5A tube failed, shortly after replacing the bottom LED and rewiring the ersatz plate lead, which led me to rebuild the whole thing with SK6812 RGBW LEDs. So I printed all the plastic parts again, because the duodecar tube socket’s pin circle can fit into a hard drive platter’s unmodified 25 mm hole, then drilled another platter to suit:

The hole under the drill fits the 3.5 mm stereo socket for the ersatz plate lead, so it’s bigger than before.

I’ve switched from Arduino Pro Minis with a separate USB converter to Arduino Nanos with an on-board CH340 USB chip, because the fake FTDI chips on the converters are a continuing aggravation:

21HB5A base - interior — 21HB5A base – interior

Adding those wire slots to the sockets definitely helps tidy things up; the wires no longer need a crude cable tie anchoring them to the socket mounting screws.

I wanted to drive the LEDs from the A7 pin, rather than the A3 pin I’d been using on the Pro Minis, to keep the wires closer together, but it turns out that A6 and A7 can’t become digital output pins. So I used A5, although I may come to regret the backward incompatibility.

In any event, the 21HB5A tube looks spiffy with its new LEDs in full effect:

21HB5A with RBGBW LEDs - cyan violet phase — 21HB5A with RBGBW LEDs – cyan violet phase

I dialed the white LED PWM down to 32, making the colors somewhat pastel, rather than washed-out.

The Arduino source code as a GitHub Gist:

	// Neopixel mood lighting for vacuum tubes
	// Ed Nisley – KE4ANU – June 2016
	// September 2016 – Add Morse library and blinkiness
	// October 2016 – Set random colors at cycle end
	// March 2017 – RGBW SK6812 LEDs

	#include <Adafruit_NeoPixel.h>
	#include <morse.h>
	#include <Entropy.h>

	//———-
	// Pin assignments

	const byte PIN_NEO = A5; // DO – data out to first Neopixel

	const byte PIN_HEARTBEAT = 13; // DO – Arduino LED

	#define PIN_MORSE 12

	//———-
	// Constants

	// number of pixels
	#define PIXELS 2

	// index of the Morse output pixel and how fast it sends
	boolean Send_Morse = false;
	#define PIXEL_MORSE (PIXELS – 1)
	#define MORSE_WPM 10

	// lag between adjacent pixel, degrees of slowest period
	#define PIXELPHASE 45

	// update LEDs only this many ms apart (minus loop() overhead)
	#define UPDATEINTERVAL 50ul
	#define UPDATEMS (UPDATEINTERVAL – 1ul)

	// number of steps per cycle, before applying prime factors
	#define RESOLUTION 500

	//———-
	// Globals

	// instantiate the Neopixel buffer array

	Adafruit_NeoPixel strip = Adafruit_NeoPixel(PIXELS, PIN_NEO, NEO_GRBW + NEO_KHZ800);

	uint32_t FullWhite = strip.Color(255,255,255,255);
	uint32_t FullOff = strip.Color(0,0,0,0);
	uint32_t MorseColor;

	struct pixcolor_t {
	unsigned int Prime;
	unsigned int NumSteps;
	unsigned int Step;
	float StepSize;
	float Phase;
	byte MaxPWM;
	};

	unsigned int PlatterSteps;

	byte PrimeList[] = {3,5,7,13,19,29};

	// colors in each LED
	enum pixcolors {RED, GREEN, BLUE, WHITE, PIXELSIZE};

	struct pixcolor_t Pixels[PIXELSIZE]; // all the data for each pixel color intensity

	uint32_t UniColor;

	unsigned long MillisNow;
	unsigned long MillisThen;

	// Morse code

	char * MorseText = " cq cq cq de ke4znu";

	LEDMorseSender Morse(PIN_MORSE, (float)MORSE_WPM);

	uint8_t PrevMorse, ThisMorse;

	//– Figure PWM based on current state

	byte StepColor(byte Color, float Phi) {

	byte Value;

	Value = (Pixels[Color].MaxPWM / 2.0) * (1.0 + sin(Pixels[Color].Step * Pixels[Color].StepSize + Phi));

	// Value = (Value) ? Value : Pixels[Color].MaxPWM; // flash at dimmest points for debug

	return Value;
	}

	//– Select three unique primes for the color generator function
	// Then compute all the step parameters based on those values

	void SetColorGenerators(void) {

	Pixels[RED].Prime = PrimeList[random(sizeof(PrimeList))];

	do {
	Pixels[GREEN].Prime = PrimeList[random(sizeof(PrimeList))];
	} while (Pixels[RED].Prime == Pixels[GREEN].Prime);

	do {
	Pixels[BLUE].Prime = PrimeList[random(sizeof(PrimeList))];
	} while (Pixels[BLUE].Prime == Pixels[RED].Prime \|\|
	Pixels[BLUE].Prime == Pixels[GREEN].Prime);
	do {
	Pixels[WHITE].Prime = PrimeList[random(sizeof(PrimeList))];
	} while (Pixels[WHITE].Prime == Pixels[RED].Prime \|\|
	Pixels[WHITE].Prime == Pixels[GREEN].Prime \|\|
	Pixels[WHITE].Prime == Pixels[BLUE].Prime);


	printf("Primes: %d %d %d %d\r\n",Pixels[RED].Prime,Pixels[GREEN].Prime,Pixels[BLUE].Prime,Pixels[WHITE].Prime);

	Pixels[RED].MaxPWM = 255;
	Pixels[GREEN].MaxPWM = 255;
	Pixels[BLUE].MaxPWM = 255;
	Pixels[WHITE].MaxPWM = 32;

	unsigned int PhaseSteps = (unsigned int) ((PIXELPHASE / 360.0) *
	RESOLUTION * (unsigned int) max(max(max(Pixels[RED].Prime,Pixels[GREEN].Prime),Pixels[BLUE].Prime),Pixels[WHITE].Prime));
	printf("Pixel phase offset: %d deg = %d steps\r\n",(int)PIXELPHASE,PhaseSteps);


	for (byte c=0; c < PIXELSIZE; c++) {
	Pixels[c].NumSteps = RESOLUTION * Pixels[c].Prime; // steps per cycle
	Pixels[c].StepSize = TWO_PI / Pixels[c].NumSteps; // radians per step
	Pixels[c].Step = random(Pixels[c].NumSteps); // current step
	Pixels[c].Phase = PhaseSteps * Pixels[c].StepSize;; // phase in radians for this color

	printf(" c: %d Steps: %d Init: %d Phase: %d deg",c,Pixels[c].NumSteps,Pixels[c].Step,(int)(Pixels[c].Phase * 360.0 / TWO_PI));
	printf(" PWM: %d\r\n",Pixels[c].MaxPWM);
	}
	}

	//– Helper routine for printf()

	int s_putc(char c, FILE *t) {
	Serial.write(c);
	}

	//——————
	// Set the mood

	void setup() {

	pinMode(PIN_HEARTBEAT,OUTPUT);
	digitalWrite(PIN_HEARTBEAT,LOW); // show we arrived

	Serial.begin(57600);
	fdevopen(&s_putc,0); // set up serial output for printf()

	printf("Vacuum Tube Mood Light – RGBW\r\nEd Nisley – KE4ZNU – March 2017\r\n");

	Entropy.initialize(); // start up entropy collector

	// set up pixels

	strip.begin();
	strip.show();

	// lamp test: a brilliant white flash

	printf("Lamp test: flash white\r\n");

	for (byte i=0; i<5 ; i++) {
	for (int j=0; j < strip.numPixels(); j++) { // fill LEDs with white
	strip.setPixelColor(j,FullWhite);
	}
	strip.show();
	delay(500);

	for (int j=0; j < strip.numPixels(); j++) { // fill LEDs with black
	strip.setPixelColor(j,FullOff);
	}
	strip.show();
	delay(500);
	}

	// get an actual random number

	uint32_t rn = Entropy.random();

	printf("Random seed: %08lx\r\n",rn);
	randomSeed(rn);

	// set up the color generators

	SetColorGenerators();

	// set up Morse generator

	Morse.setup();
	Morse.setMessage(String(MorseText));
	MorseColor = strip.Color(255,random(32,64),random(16),0);

	PrevMorse = ThisMorse = digitalRead(PIN_MORSE);

	printf("Morse enabled: %d at %d wpm color: %08lx\n [%s]\r\n",Send_Morse,MORSE_WPM,MorseColor,MorseText);

	MillisNow = MillisThen = millis();

	}

	//——————
	// Run the mood

	void loop() {

	if (!Morse.continueSending()) {
	printf("Restarting Morse message\r\n");
	Morse.startSending();
	}
	ThisMorse = digitalRead(PIN_MORSE);

	MillisNow = millis();
	if (((MillisNow – MillisThen) >= UPDATEMS) \|\| // time for color change?
	(PrevMorse != ThisMorse)) { // Morse output bit changed?

	digitalWrite(PIN_HEARTBEAT,HIGH);

	if (Send_Morse && ThisMorse) { // if Morse output high, overlay flash
	strip.setPixelColor(PIXEL_MORSE,MorseColor);
	}
	PrevMorse = ThisMorse;
	strip.show(); // send out precomputed colors

	boolean CycleRun = false; // check to see if all cycles have ended
	for (byte c=0; c < PIXELSIZE; c++) { // compute next increment for each color
	if (++Pixels[c].Step >= Pixels[c].NumSteps) {
	Pixels[c].Step = 0;
	printf("Cycle %d steps %d at %8ld delta %ld ms\r\n",c,Pixels[c].NumSteps,MillisNow,(MillisNow – MillisThen));
	}
	else {
	CycleRun = true; // this color is still cycling
	}
	}

	// If all cycles have completed, reset the color generators

	if (!CycleRun) {
	printf("All cycles ended: setting new color generator values\r\n");
	SetColorGenerators();
	}

	for (int i=0; i < strip.numPixels(); i++) { // for each pixel
	byte Value[PIXELSIZE];
	for (byte c=0; c < PIXELSIZE; c++) { // … for each color
	Value[c] = (Pixels[c].MaxPWM / 2.0) * (1.0 + sin(Pixels[c].Step * Pixels[c].StepSize – i*Pixels[c].Phase));
	}
	UniColor = strip.Color(Value[RED],Value[GREEN],Value[BLUE],Value[WHITE]);
	strip.setPixelColor(i,UniColor);
	}

	MillisThen = MillisNow;
	digitalWrite(PIN_HEARTBEAT,LOW);
	}

	}

view raw TubeMorse.ino hosted with ❤ by GitHub

2017-03-22

Kitchen Sink Faucet Deck Sealing

I had to replace the faucet on a kitchen sink (not our own, for reasons not relevant here) after the steel nuts & washers holding the base to the sink deck rotted completely away. Why faucet manufacturers used plain steel in that location remains a mystery; I’m sure it has something to do with cost reduction and damn the consequences after a few years.

Of course, the new faucet didn’t sit quite flat on the sink deck, due to the raised rim around the perimeter. Installing it like that would prevent the (hard plastic) gasket from sealing against the deck, with the inevitable water leak below the sink; we started this project by scrapping a water-soaked shelf under the sink due to the previous faucet’s wrecked seal. Sliding the oval base forward enough to clear the rim would expose the two holes on each side, with similar results.

You can see the problem if you squint hard enough:

Kitchen Sink Faucet – gasket mask

I decided raising the back of the base by maybe two millimeters wouldn’t be particularly visible, particularly if I filled the space with silicone snot (almost) matching the gasket to provide a solid foundation.

The blue tape masks the sink surface around the gasket to prevent silicone mishaps and simplify cleanup. I held the gasket in place, traced around it with new Xacto knife blade, and peeled the inside out just like I knew what I was doing.

Generous beads of snot around all the holes and across the back will provide a firm base and a good seal:

Kitchen Sink Faucet – gasket in place

With that in place, I aligned the faucet over the gasket, gently tightened the nuts holding the base to the deck, and waited a day for the silicone to start curing before completing the plumbing. It’ll take a while to finish, due to the limited area exposed around the edges.

The water lines now have shutoff ball valves, which the next person to work on it will surely appreciate.

2017-03-19

Category: Machine Shop

Amazon EK3211 Kitchen Scale

Bosch Laser Rangefinder Corrosion

Kensington Expert Mouse Cable Replacement

AADE LC Meter: AT26 Crystal Capacitance Fixture

Quartz Tuning Fork Resonator Teardown

Vacuum Tube Lights: Duodecar Rebuild

Kitchen Sink Faucet Deck Sealing