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.

Author: Ed

USB Testers vs. Reality
Set up a test harness with a USB tester between two amputated USB cables:

USB Testers – Keweisi plugged

Input comes from a bench power supply:

USB Testers – 5 V input clips

Output goes to an 8 Ω power resistor:

USB Testers – 8 ohm load

Yes, it’s mounted on the isothermal block from back in the Thing-O-Matic days, disspating barely 2 W. Thermocouples FTW, but in this case I don’t care about the temperature.

Because these are random USB cables, they come with the usual caveats. Indeed, I measured a 9.8 Ω loop resistance (!) at the input end. The resistor is slightly under 8Ω, so the 1.8 Ω wire resistance suggests (at least) one of the USB cables contains very little copper. That’s measured without the USB tester in series, because it tries really hard to power up from the ohmmeter’s source voltage and basically shorts out the resistor.

Both testers accurately report the source voltage with no load, so I presume the voltage shown with current flowing through the resistor represents the actual voltage at the tester. The source cable drops a substantial voltage under load.

The 8 Ω resistor should draw 5 V / 8 Ω = 625 mA at 5 V. The voltmeter probes provide a non-intrusive way to measure the actual current by working backwards: current = volts / 8 Ω. As it turned out, the resistor sees less than 4 V with the bench supply set to 5.0 V.

So, we begin.

With the bench supply at 5.5 V, the Keweisi meter shows 4.9 V and 0.48 A with 4.0 V across the resistor for an actual 500 mA current. The source cable drops 600 mV, indicating a wire resistance of 1.2 Ω, about 2/3 of the total wire resistance.

The anonymous meter produces two different results for an actual 500 mA current, depending on nothing under my control:
- Supply 5.3 V, indicated 5.0 V and 0.5 A
- Supply 5.1 V, indicated 4.76 V and 0.5 A
Both results show about 300 mV source drop, half of the Keweisi meter’s 600 mV, suggesting a wire resistance of 0.6 Ω. The meter displays a blinking ▲, presumably indicating the input voltage is kinda high.

I have no explanation.

After the meters measured an actual 500 mA load for about an hour:
- Keweisi: 1.6 hr → 782 mA·h, should be 800 mA·h
- Anonymous: 1.0 hr → 515 mA·h, should be 500 mA·h
Which roughly agrees with the battery charge data:

USB Testers – Charge vs Runtime

The anonymous meter seems reasonably accurate, the Keweisi meter undershoots by 2.5%, and they’re both Close Enough for simple measurements.

There’s probably a duty cycle effect, too, because the battery charger presents a pulsed load, but I’m just not going to worry about it.
2020-06-08
Robin Nest: Eggs!
After pausing to recover from construction, Ms Robin laid four eggs in four days:
Garage Robin Nest – first egg – 2020-05-28
Garage Robin Nest – 2 eggs – 2020-05-29
Garage Robin Nest – 3 eggs – 2020-05-30
Garage Robin Nest – 4 eggs – 2020-05-31
She’s surprisingly tolerant of our comings and goings, as well as garage door openings and closings:

Garage Robin Nest – robin brooding

We’re trying to stay out of her way as much as possible.

The gallery pix come from my phone, held against the soffit over the nest, and aimed entirely by feel, while standing on the Greater Ladder. If I had access to the top of the soffit, I’d drill a webcam hole, but …
2020-06-07
Tree Stump Removal

This makes writing 3D modeling code and turning threads look downright attractive:

Tree stump – crater

The previous owners apparently surrounded a cedar (?) tree with a ring of large, decorative rocks. The tree vanished long before we arrived, with the stump accreting random stones, bricks, and similar impedimenta ever since; my first task involved (re)moving a couple hundred pounds of rocky debris.

After using the stump as a fulcrum for that steel bar to break the rotted roots and loosen the surrounding soil, it’s out and away:

Tree stump – excavated

Back to the Basement Laboratory …

2020-06-06
Screw Thread Measurement

While I was cutting threads for the Floor Lamp poles, I tried measuring my progress over wires:

Floor Lamp – tube fitting – thread measurement

Those are three lengths of music wire, slightly bent from their storage roll, held in place with a ~~precision clamp~~ metric micrometer. Given the crudity of the setup, the uncalibrated wire diameter, and my lack of thread-fu, the results came out both close and unconvincing.

A set of real thread measuring wires being cheap & readily available, I’m prepared for the next time around this block:

Thread Measuring Wires – eBay set

The 185 mil “wires” (they’re all allegedly ground rod) will let me cut threads matching things like a Jesus nut; they’re suited for 3 TPI / 8 mm pitch screws. Mostly, wires from the front row will be all I ever need.

Which look like this in action:

Thread Measuring Wires – eBay setThread Measuring Wires – detail

The black doodad (the set includes half a dozen for all the wire sizes) fits over the micrometer anvil and holds two wires betwixt anvil and screw, leaving me to manipulate the screw, the third wire, and the micrometer with my remaining hands. Hence the vise holding the micrometer, which is known to be Very Bad Practice.

From the side:

Thread Measuring Wires – overview

All of the smaller wires measure 0.5 mil too thin, which is likely due to my lack of calibrated measurement equipment:

Thread Measuring Wires – scant 24 mil

The few thread pitch diameters I measured also came out slightly too small, again likely due to calibration and screw tolerances.

The LittleMachineShop description of measuring threads over wires seems entirely adequate.

To forestall link rot, a slightly rearranged version of their tables of wire constants:

Thread Wire Measurement Constants

The lower table has metric thread pitches with the wire sizes in inches.

You measure the distance over the recommended wire (in inches or millimeters, as appropriate), subtract the constant, and get the pitch diameter in the same units. Conversely, add the constant to the desired pitch diameter to get the target over-wire distance, carefully cut the thread until it measures a bit less than that, back up sixty seconds, and cut it spot on.

Verily, it is written: there is no UnDo key (⎌) in machine shop work.

2020-06-05
More WS2812 Failures

Even though I’m using what seem to be good-quality parts, one of the WS2812 RGB LEDs in a Glass Tile frame died:

Glass Tile – 2×2 – first WS2812B failure

It passed the Josh Sharpie Test:

Glass Tile – WS2812 failure – PCB unknown

After building the third Glass Tile unit, one of the LEDs didn’t light up due to an easily diagnosed problem:

Glass Tile – WS2812 failure – PCB cold solder – as found

A closer look:

Glass Tile – WS2812 failure – PCB cold solder

Shortly thereafter, the Nissan Fog Lamp developed an obvious beam problem:

Nissan Fog Lamp – failed WS2812 effect

The WS2812 had the proper voltages / signals at all its pins and was still firmly stuck to the central “heatsink”:

Nissan Fog Lamp – failed WS2812 detail

It also passed the Josh Sharpie Test:

Glass Tile – WS2812 failure – tape – unknown

I’m particularly surprised by this one, because eleven of the twelve flex-PCB WS2812s in the Hard Drive Platter light have been running continuously for years with no additional failures.

The alert reader will note the common factor: no matter what substrate the LED is (supposed to be) soldered to, no matter when I bought it, no matter what it’s wired into, a WS2812 will fail.

They’re all back in operation:

Glowing Algorithmic Art

Although nobody knows for how long …

Obviously, it’s time to refresh my programmable RGB LED stockpile!

2020-06-04

PiHole with DNS-over-HTTP: Revised

More than a year later, the PiHole continues to work fine, but the process for installing the Cloudflare DoH machinery has evolved.

(And, yes, it’s supposed to be DNS-over-HTTPS. So it goes.)

To forestall link rot, the key points:

cd /tmp ;  wget https://bin.equinox.io/c/VdrWdbjqyF/cloudflared-stable-linux-arm.tgz
tar -xvzf cloudflared-stable-linux-arm.tgz 
sudo cp cloudflared /usr/local/bin
sudo chmod +x /usr/local/bin/cloudflared
sudo cloudflared -v
sudo useradd -s /usr/sbin/nologin -r -M cloudflared
sudo nano /etc/default/cloudflared
----
CLOUDFLARED_OPTS=--port 5053 --upstream https://1.1.1.1/dns-query --upstream https://1.0.0.1/dns-query 
----
sudo chown cloudflared:cloudflared /etc/default/cloudflared
sudo chown cloudflared:cloudflared /usr/local/bin/cloudflared
sudo nano /etc/systemd/system/cloudflared.service
----
[Unit]
Description=cloudflared DNS over HTTPS proxy
After=syslog.target network-online.target

[Service]
Type=simple
User=cloudflared
EnvironmentFile=/etc/default/cloudflared
ExecStart=/usr/local/bin/cloudflared proxy-dns $CLOUDFLARED_OPTS
Restart=on-failure
RestartSec=10
KillMode=process

[Install]
WantedBy=multi-user.target
----
sudo systemctl enable cloudflared
sudo systemctl start cloudflared
sudo systemctl status cloudflared

Then aim PiHole’s DNS at 127.0.0.1#5053. It used to be on port #54, for whatever that’s worth.

Verify it at https://1.1.1.1/help, which should tell you DoH is in full effect.

To update the daemon, which I probably won’t remember:

wget https://bin.equinox.io/c/VdrWdbjqyF/cloudflared-stable-linux-arm.tgz
tar -xvzf cloudflared-stable-linux-arm.tgz
sudo systemctl stop cloudflared
sudo cp ./cloudflared /usr/local/bin
sudo chmod +x /usr/local/bin/cloudflared
sudo systemctl start cloudflared
cloudflared -v
sudo systemctl status cloudflared

And then It Just Works … again!

2020-06-03

Garden Hose Valve Wrench: Reinforced

After five gardening seasons, my simple 3D printed wrench broke:

Hose Valve Knob - fractured — Hose Valve Knob – fractured

Although Jason’s comment suggesting carbon-fiber reinforcing rods didn’t prompt me to lay in a stock, ordinary music wire should serve the same purpose:

Hose Valve Knob - cut pins — Hose Valve Knob – cut pins

The pins are 1.6 mm diameter and 20 mm long, chopped off with hardened diagonal cutters. Next time, I must (remember to) grind the ends flat.

The solid model needs holes in appropriate spots:

Hose Valve Knob - Reinforced - Slic3r — Hose Valve Knob – Reinforced – Slic3r

Yes, I’m going to put round pins in square holes, without drilling the holes to the proper diameter: no epoxy, no adhesive, just 20 mm of pure friction.

The drill press aligns the pins:

Hose Valve Knob - pin ready — Hose Valve Knob – pin ready

And rams them about halfway down:

Hose Valve Knob - pin midway — Hose Valve Knob – pin midway

Close the chuck jaws and shove them flush with the surface:

Hose Valve Knob - pins installed — Hose Valve Knob – pins installed

You can see the pins and their solid plastic shells through the wrench stem:

Hose Valve Knob - assembled — Hose Valve Knob – assembled

Early testing shows the reinforced wrench works just as well as the previous version, even on some new valves sporting different handles, with an equally sloppy fit for all. No surprise: I just poked holes in the existing model and left all the other dimensions alone.

The OpenSCAD source code as a GitHub Gist:

	// Hose connector knob
	// Ed Nisley KE4ZNU – June 2015
	// 2020-05 add reinforcing rods

	Layout = "Build"; // [Knob, Stem, Show, Build]

	RodHoles = true;

	//- Extrusion parameters – must match reality!

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

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

	Protrusion = 0.1;

	HoleWindage = 0.2;

	//——
	// Dimensions

	/* [Dimensions] */

	RodOD = 1.6;
	RodAngle = 35;

	/* [Hidden] */

	StemOD = 30.0; // max OD for valve-to-valve clearance

	BossOD = 16.0; // single-ended handle boss

	SlotWidth = 13.0;
	SlotHeight = 10.0;

	StemInset = 10.0;
	StemLength = StemInset + SlotHeight + 25.0;
	StemSides = 2*4;

	Align = 0180/StemSides; // 1 produces thinner jaw ends

	KnobOD1 = 70; // maximum dia without chamfer
	KnobOD2 = 60; // top dia

	KnobSides = 4*4;

	DomeHeight = 12; // dome shape above lobes

	KnobHeight = DomeHeight + 2*SlotHeight;

	DomeOD = KnobOD2 + (KnobOD1 – KnobOD2)*(DomeHeight/KnobHeight);

	DomeArcRad = (pow(KnobHeight,2) + pow(DomeOD,2)/4) / (2*DomeHeight);

	RodBCD = (StemOD + BossOD)/2;

	//- 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);
	}

	//– Stem for valve handles

	module Stem() {

	difference() {
	rotate(Align)
	cylinder(d=StemOD,h=StemLength,$fn=StemSides);
	translate([0,0,SlotHeight/2 – Protrusion/2])
	cube([2*StemOD,SlotWidth,(SlotHeight + Protrusion)],center=true);
	translate([0,0,-Protrusion])
	cylinder(d=BossOD,h=SlotHeight,$fn=2*StemSides);
	if (RodHoles)
	for (i=[-1:1])
	rotate(i*RodAngle + 90)
	for (j=[-1,1])
	translate([j*RodBCD/2,0,-Protrusion])
	rotate(180/4)
	PolyCyl(RodOD,2*SlotHeight,4);
	}

	}


	//– Hand-friendly knob

	module KnobCap() {
	difference() {
	scale([1.0,0.75,1.0])
	rotate(180/KnobSides)
	intersection() {
	translate([0,0,(KnobHeight-DomeArcRad)])
	sphere(r=DomeArcRad,$fa=180/KnobSides);
	cylinder(r1=KnobOD1/2,r2=KnobOD2/2,h=KnobHeight,$fn=KnobSides);
	cylinder(r1=KnobOD2/2,r2=KnobOD1/2,h=KnobHeight,$fn=KnobSides);
	}
	translate([0,0,-Protrusion])
	rotate(Align)
	cylinder(d=(StemOD + 2*ThreadWidth),h=(StemInset + Protrusion),$fn=StemSides);
	}
	}

	//- Build it


	if (Layout == "Knob")
	KnobCap();

	if (Layout == "Stem")
	Stem();

	if (Layout == "Build") {
	translate([-KnobOD1/2,0,0])
	KnobCap();
	translate([StemOD/2,0,StemLength])
	rotate([180,0,0])
	Stem();
	}

	if (Layout == "Show") {
	translate([0,0,0])
	Stem();
	translate([0,0,StemLength – StemInset])
	KnobCap();
	}

view raw Hose Connector Knob.scad hosted with ❤ by GitHub

2020-06-02

Author: Ed

USB Testers vs. Reality

Robin Nest: Eggs!

Tree Stump Removal

Screw Thread Measurement

More WS2812 Failures

PiHole with DNS-over-HTTP: Revised

Garden Hose Valve Wrench: Reinforced