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

Blog Backup

Recent news about Dropbox removing its Public folder feature reminded me to do my every-other-month blog backup. Wordpress provides a method to “export” the blog’s text and metadata in their XML-ish format, so you can (presumably) import your blog into another WordPress instance on the server of your choice. However, the XML file (actually, ten of ’em, all tucked into a paltry 8 MB ZIP file) does not include the media files referenced in the posts, which makes sense.

Now, being that type of guy, I have the original media files (mostly pictures) tucked away in a wide variety of directories on the file server. The problem is that there’s no easy way to match the original file to the WordPress instance; I do not want to produce a table by hand.

Fortunately, the entry for each blog post labels the URL of each media file with a distinct XML tag:

		<wp:attachment_url>https://softsolder.com/wp-content/uploads/2008/12/cimg2785-blender-bearings.jpg</wp:attachment_url>

Note the two leading tabs: it’s prettyprinted XML. (Also, should you see escaped characters instead of < and >, then WordPress has chewed on the source code again.)

While I could gimmick up a script (likely in Python) to process those files, this is simple enough to succumb to a Bash-style BFH:

grep attachment_url *xml > attach.txt
sed 's/^.*http/http/' attach.txt | sed 's/&lt;\/wp.*//' > download.txt
wget --no-verbose --wait=5 --random-wait --force-directories --directory-prefix=/where/I/put/WordPress/Backups/Media/ -i download.txt

That fetches 6747 media files = 1.3 GB, tucks them into directories corresponding to their WordPress layout, and maintains their original file dates. I rate-limited the download to an average of 5 s/file in the hope of not being banned as a pest, so the whole backup takes the better part of ten hours.

So I wind up blowing an extra gig of disk space on a neatly arranged set of media files that can (presumably) be readily restored to another WordPress instance, should the occasion arise.

Memo to Self: investigate applying the -r option to the base URL, with the -N option to make it incremental, for future updates.

2016-12-22

Under-cabinet Lamp Brackets: Angled Edition

The LED strip lights have a reasonably diffuse pattern with an on-axis bright area that puts more light on the rear of the counter than seems strictly necessary. Revising the original brackets to tilt the strips moves the bright patch half a foot forward:

Kitchen Light Bracket - angled - solid model — Kitchen Light Bracket – angled – solid model

For lack of anything smarter, the angle puts the diagonal of the LED strip on the level:

Kitchen Light Bracket - angled - Slic3r preview — Kitchen Light Bracket – angled – Slic3r preview

The translucent block represents the strip (double-thick and double-wide), with a peg punching a hole for the threaded brass insert.

Although the source code has an option to splice the middle blocks together, it can also build them separately:

Kitchen Light Bracket - angled - LED block — Kitchen Light Bracket – angled – LED block

Turns out they’re easier to assemble that way; screw ’em to the strips, then screw the strips to the cabinet.

I moved the deck screw holes to the other end of the block, thus putting the strips against the inside of the cabinet face. It turns out the IR sensor responds to the DC level of the reflected light, not short-term changes, which meant the reflection from the adjacent wood blinded it to anything waved below. Adding a strip of black electrical tape killed enough of the reflected light to solve that problem:

Under-cabinet light - IR sensor shield — Under-cabinet light – IR sensor shield

The tape isn’t quite as far off-center as it looks, but I’m glad nobody will ever see it …

The before-and-after light patterns, as viewed on B-size metric graph paper centered on the left-hand strip and aligned with the belly side of the countertop:

Under-cabinet light - straight vs angled patterns — Under-cabinet light – straight vs angled patterns

Those look pretty much the same, don’t they? So much for photography as evidence for anything.

The OpenSCAD source code as a GitHub Gist:

	// Mounting brackets for eShine under-counter LED lights
	// Ed Nisley KE4ZNU December 2016

	Layout = "Build";

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———-
	// Dimensions

	MountHeight = (1 + 03/16) inch; // distance from cabinet bottom

	THREADOD = 0;
	HEADOD = 1;
	LENGTH = 2;

	WoodScrew = [4.0,8.3,41]; // 8×1-5/8 Deck screw
	WoodScrewRecess = 3.0;
	WoodScrewMargin = 1.5 * WoodScrew[HEADOD]; // head OD + flat ring

	Insert = [3.9,4.6,5.8 + 2.0]; // 4-40 knurled brass insert

	JoinerLength = 19.0; // joiner between strips

	LEDEndBlock = [11.0,28.8,9.5]; // LED plastic end block
	LEDScrewOffset = [1.0,8.2,0]; // hole offset from end block center point

	StripAngle = atan2(LEDEndBlock[2],LEDEndBlock[1]);
	echo(str("Strip angle: ",StripAngle));

	MountBlock = [WoodScrewMargin,(WoodScrewMargin + LEDEndBlock[1]*cos(StripAngle)),MountHeight];

	//———————-
	// 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(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
	}

	//—–
	// LED end block with positive insert for subtraction
	// returned with mounting hole end of strip along X axis
	// ready for positioning & subtraction

	module EndBlock(Side = "L") {

	LSO = [((Side == "L") ? 1 : -1)*LEDScrewOffset[0],LEDScrewOffset[1],LEDScrewOffset[2]];

	rotate([-StripAngle,0,0])
	translate([0,LEDEndBlock[1]/2,LEDEndBlock[2]])
	union() {
	cube(LEDEndBlock + [LEDEndBlock[0],0,LEDEndBlock[2]],center=true);
	translate(LSO + [0,0,-(LEDEndBlock[2] + Insert[2])])
	rotate(180/6)
	PolyCyl(Insert[1],2*Insert[2],6);
	}
	}

	//—–
	// End mounting block with proper hole offsets

	module EndMount(Side = "L") {

	translate([0,0,MountBlock[2]/2])
	difference() {
	translate([0,MountBlock[1]/2,0])
	cube(MountBlock,center=true);

	translate([0,WoodScrewMargin,MountBlock[2]/2])
	EndBlock(Side);

	translate([0,WoodScrewMargin/2,-MountBlock[2]])
	rotate(180/6)
	PolyCyl(WoodScrew[THREADOD],2*MountBlock[2],6);

	translate([0,WoodScrewMargin/2,(MountBlock[2]/2 – WoodScrewRecess)])
	rotate(180/6)
	PolyCyl(WoodScrew[HEADOD],WoodScrewRecess + Protrusion,6);

	translate([((Side == "L") ? 1 : -1)MountBlock[0]/2,3MountBlock[1]/4,-MountBlock[2]/4])
	rotate([90,0,((Side == "L") ? 1 : -1)*90])
	translate([0,0,-2*ThreadThick])
	linear_extrude(height=4*ThreadThick,convexity=3)
	text(Side,font=":style=bold",valign="center",halign="center");
	}
	}

	module MidMount() {
	XOffset = (JoinerLength + MountBlock[0])/2;
	BridgeThick = 5.0;

	union() {
	translate([XOffset,0,0])
	EndMount("L");

	translate([0,MountBlock[1]/2,BridgeThick/2])
	cube([JoinerLength,MountBlock[1],BridgeThick] + [2*Protrusion,0,0],center=true);

	translate([-XOffset,0,0])
	EndMount("R");
	}
	}

	//———-
	// Build them

	if (Layout == "EndBlock")
	EndBlock("L");

	if (Layout == "EndMount")
	EndMount("R");

	if (Layout == "MidMount")
	MidMount();

	if (Layout == "BuildJoined") {
	translate([-(JoinerLength + 2*MountBlock[0]),0,0])
	EndMount("L");

	MidMount();

	translate([(JoinerLength + 2*MountBlock[0]),0,0])
	EndMount("R");
	}

	if (Layout == "Build") {
	translate([-MountBlock[0],0,0])
	EndMount("L");

	translate([MountBlock[0],0,0])
	EndMount("R");
	}

view raw

Kitchen Light Bracket – angled.scad

hosted with ❤ by GitHub

2016-12-20

Quilt Blocks: Scan and Montage

Mary has been working on the Splendid Sampler project, with 56 completed blocks (*) stacked on her sewing table. We agreed that those blocks would make a nice background for our Christmas Letter, but the labor involved to photograph all the fabric squares and turn them into a page seemed daunting.

Turned out it wasn’t all that hard, at least after we eliminated all the photography and hand-editing.

The 6½x6½ inch blocks include a ¼ inch seam allowance on all sides and, Mary being fussy about such things, they’re all just about perfect. I taped a template around one block on the scanner glass:

Then set XSane to scan at 150 dpi and save sequentially numbered files, position a square scan area over the middle of the template, and turn off all the image enhancements to preserve a flat color balance.

With “picture taking” reduced to laying each square face-down on the glass, closing the lid, and clicking Scan, the scanner’s throughput became the limiting factor. She scanned the blocks in the order of their release, while tinkering the auto-incremented file number across the (few) gaps in her collection, to produce 56 files with unimaginative auto-generated names along the lines of Block 19.jpg, thusly:

The “square” images were 923×933 pixels, just slightly larger than the ideal finished size of 6 inch × 150 dpi = 900 pixel you’d expect, because we allowed a wee bit (call it 1/16 inch) on all sides to avoid cutting away the sharp points and, hey, I didn’t get the scan area exactly square.

With the files in hand, turning them into a single page background image requires a single Imagemagick incantation:

montage -verbose B*jpg -density 150 -geometry "171x173+0+0" -tile "7x" Page.jpg

I figured the -geometry value to fill the 8 inch page width at 150 dpi, which is good enough for a subdued background image: 8 inch × 150 dpi / 7 images = 171 pixels. Imagemagick preserves the aspect ratio of the incoming images during the resize, so, because these images are slightly higher than they are wide, the height must be slightly larger to avoid thin white borders in the unused space. With all that figured, you get a 1197×1384 output image.

Bumping the contrast makes the colors pop, even if they’re not quite photo-realistic:

Quilt block montage - contrast — Quilt block montage – contrast

I’ll lighten that image to make the Christmas Letter text (in the foreground, atop the “quilt”) readable, which is all in the nature of fine tuning.

She has 40-odd blocks to go before she can piece them together and begin quilting, with a few other projects remaining to be finished:

(*) She’s a bit behind the block schedule, having had a year of gardening, bicycling, and other quilting projects, plus whatever else happens around here. Not a problem, as we see it.

2016-12-19

60 kHz Preamp: Simulation

This circuitry descends directly from a QEX article (Nov/Dec 2015, p 13) by John Magliacane, KD2BD: A Frequency Standard for Today’s WWVB. The key part, at least for me, is a 60 kHz preamplifier using a resonant-tuned loop antenna and an instrumentation amplifier to reject common-mode interference from local electrostatic fields.

I tinkered up an LTSpice IV simulation using somewhat more contemporary parts (clicky for more dots):

60 kHz Preamp - LTSpice schematic — 60 kHz Preamp – LTSpice schematic

The simulation quickly revealed that the original schematic interchanged the filter amp’s pins 2 and 3; the filter doesn’t work at all when you swap the + and – inputs.

The stuff in the dotted box fakes the loop antenna parameters, with a small differential AC signal that injects roughly the right voltage to simulate a nominal 100 µV/m WWVB field strength. I biased the center tap to the DC virtual ground at + 10 V and bypassed it to circuit common, so the RF should produce a nice differential signal about the virtual ground. The 5 kΩ resistors provide ESD protection and should help tamp down damage from nearby lightning strikes and suchlike.

It works pretty much as you’d expect:

60 kHz Preamp - Frequency Response — 60 kHz Preamp – Frequency Response

The LT1920 is mostly flat with 40 dB gain out through 60 kHz, although the actual hardware becomes a nice oscillator with that much gain; my layout and attention to detail evidently leaves a bit to be desired. The LF353 implements a multiple-feedback bandpass filter with about 20 dB of gain; its 4 MHz GBW gives it enough headroom. The LT1010 can drive 150 mA and, with a bit of luck and AC coupling, will feed a 50 Ω SDR input just fine.

This obviously turns into a Circuit Cellar column: March 2017, if you’re waiting by the mailbox.

2016-12-16

Kenmore Progressive Vacuum Tool Adapters: Second Failure

Pretty much as expected, the dust brush nozzle failed again, adjacent to the epoxy repair:

Dust brush adapter - second break — Dust brush adapter – second break

A bit of rummaging turned up some ¾ inch Schedule 40 PVC pipe which, despite the fact that no plumbing measurement corresponds to any physical attribute, had about the right OD to fit inside the adapter’s ID:

Dust brush - PVC reinforcement — Dust brush – PVC reinforcement

The enlarged bore leaves just barely enough space for a few threads around the circumference. Fortunately, the pipe OD is a controlled dimension, because it must fit inside all the molded PVC elbows / tees / caps / whatever.

The pipe ID isn’t a controlled dimension and, given that the walls seemed far too thick for this purpose, I deployed the boring bar:

Dust brush adapter - reinforced tube - boring — Dust brush adapter – reinforced tube – boring

That’s probably too much sticking out of the chuck, but sissy cuts saved the day. The carriage stop keeps the boring bar 1 mm away from the whirling chuck.

Bandsaw it to length and face the ends:

Dust brush adapter - reinforcement — Dust brush adapter – reinforcement

The PVC tube extends from about halfway along the steep taper from the handle fitting out to the end, with the section closest to the handle making the most difference.

Ram it flush with the end:

Dust brush adapter - reinforced tube - detail — Dust brush adapter – reinforced tube – detail

I thought about gluing it in place, but it’s a sufficiently snug press fit that I’m sure it won’t go anywhere.

Natural PETG probably isn’t the right color:

Dust brush adapter - reinforced tube - installed — Dust brush adapter – reinforced tube – installed

Now, let’s see how long that repair lasts …

The OpenSCAD source code as a GitHub Gist:

	//——————-
	// eBay horsehair dusting brush
	// Hacked for 3/4" Schedule 40 PVC stiffening tube

	module DustBrush() {

	union() {
	translate([0,0,40.0])
	rotate([180,0,0])
	difference() {
	union() {
	cylinder(d1=EndStop[OD1],d2=31.8,h=10.0);
	translate([0,0,10.0 – Protrusion])
	cylinder(d1=32.0,d2=30.0,h=30.0 + Protrusion);
	}
	translate([0,0,-Protrusion])
	cylinder(d1=26.0,d2=24.0,h=100);
	translate([0,0,-Protrusion]) // 3/4 inch Sch 40 PVC
	PolyCyl(27.0,100);
	}
	translate([0,0,40.0 – Protrusion])
	MaleFitting();
	}
	}

view raw Kenmore Wand Bushings – Reinforced Dust Brush Adapter.scad hosted with ❤ by GitHub

2016-11-29

Cropping Images in a PDF

For reasons not relevant here, I had a PDF made from scanned page images with far too much whitespace around the Good Stuff. As with all scanned pages, the margins contain random artifacts that inhibit automagic cropping, so manual intervention was required.

Extract the images as sequentially numbered JPG files:

pdfimages -j mumble.pdf mumble

Experimentally determine how much whitespace to remove, then:

for f in mumble-0??.jpg ; do convert -verbose $f -shave 225x150 ${f%%.*}a.jpg ; done

You could use mogrify to shave the images in-place. However, not modifying the files simplifies the iteration process by always starting with the original images.

Stuff the cropped images back into a PDF:

convert mumble-0??a.jpg mumble-shaved.pdf

Profit!

2016-11-18

Compose Key Sequences for Useful Unicode Characters

If you activate a Compose key on your keyboard:

Then you can insert Unicode characters without memorizing their hex values. Of course, you must memorize the Compose key sequences. Fortunately, they’re more-or-less mnemonic for the ones I occasionally use, which are hereby cherrypicked from that list.

Press-and-release the Compose key (right-Win), then type the characters as shown to get the symbol in quotes:

o o “°” degree # DEGREE SIGN
o r “®” registered # REGISTERED SIGN
t m “™” U2122 # TRADE MARK SIGN
s m “℠” U2120 # SERVICE MARK
. . “…” ellipsis # HORIZONTAL ELLIPSIS
. – “·” periodcentered # MIDDLE DOT
. = “•” enfilledcircbullet # BULLET
+ – “±” plusminus # PLUS-MINUS SIGN (∓ MINUS-PLUS is U2213)
x x “×” multiply # MULTIPLICATION SIGN
< < “«” guillemotleft # LEFT-POINTING DOUBLE ANGLE QUOTATION MARK
> > “»” guillemotright # RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
c / “¢” cent # CENT SIGN
– – . “–” U2013 # EN DASH
– – – “—” U2014 # EM DASH
< – “←” U2190 # LEFTWARDS ARROW
| ^ “↑” U2191 # UPWARDS ARROW
– > “→” U2192 # RIGHTWARDS ARROW
| v “↓” U2193 # DOWNWARDS ARROW
= > “⇒” U21D2 # RIGHTWARDS DOUBLE ARROW
? ! “‽” U203D # INTERROBANG
p o o “💩” U1F4A9 # PILE OF POO
m u “µ” mu # MICRO SIGN
d i “⌀” U2300 # DIAMETER SIGN
1 4 “¼” onequarter # VULGAR FRACTION ONE QUARTER
1 2 “½” onehalf # VULGAR FRACTION ONE HALF
3 4 “¾” threequarters # VULGAR FRACTION THREE QUARTERS
1 1 0 “⅒” U2152 # VULGAR FRACTION ONE TENTH (and similar)
^ 1 “¹” onesuperior # SUPERSCRIPT ONE (also 0 2 3 + -…)
_ 1 “₁” U2081 # SUBSCRIPT ONE (also 0 2 3 + -…)
e ‘ “é” eacute # LATIN SMALL LETTER E WITH ACUTE
e ` “è” egrave # LATIN SMALL LETTER E WITH GRAVE

Producing Greek letters requires a “dead_greek” key, so it’s easier to start with bare hex Unicode values at U0391 (Α) and U03b1 (α) and work upward until you find what you need:

U03A3 Σ uppercase sigma
U03a9 Ω uppercase omega
U03C3 σ lowercase sigma
U03c9 ω lowercase omega
U03c4 τ lowercase tau
U03c0 π lowercase pi
U0394 Δ uppercase delta
U03F4 ϴ uppercase theta
U03B8 θ lowercase theta
U03D5 ϕ phi math symbol
U03A6 Φ uppercase phi
U03C6 φ lowercase phi

Odds and ends:

U00a0 | | non-breaking space
U2007 | | figure space (invisible digit space)
U202F | | narrow space
U2011 ‑ non-breaking hyphen
U2030 ′ prime (not quote)
U2033 ″ double-prime (not double-quote)
U2018 ‘ left single quote
U2019 ’ right single quote
U201C “ left double quote
U201D ” right double quote
U2245 ≅ approximately equal
U2264 ≤ less-than or equal
U2265 ≥ greater-than or equal
U221A √ square root
U221B ∛ cube root
U221C ∜ fourth root (yeah, right)
U221D ∝ proportional to
U2300 ⌀ diameter
U25CA ◊ lozenge

If you set the keyboard layout to US International With Dead Keys, maybe you (definitely not I) could remember all the dead keys.

2016-11-16