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

Under-cabinet Lamp Brackets: Close-fit Power Plug
Adding a little tab to the angled brackets prevents them from pivoting while you’re tightening the mounting screw into the brass insert:

Kitchen Light Bracket – angled lip – Slic3r preview

The trick with those tabs is to chop ’em off halfway to the tip, because there’s no point trying to print a wedge that ends with a sharp edge:

Kitchen Light Bracket – angled – tab cutoff – solid model

Generating & positioning that block goes a little something like this:
```
translate([0,
           2*MountBlock[1] - LEDEndBlock[2]*sin(StripAngle),
           MountBlock[2]/2 + MountHeight - 0.5*LEDEndBlock[2]*cos(StripAngle)])
    cube(2*MountBlock,center=true);
```
As a rule of thumb, there’s no point in fussing with smaller shapes when a big one will suffice…

This LED strip fits under the cabinet over the butcher block countertop next to the stove, which turns out to be Just Barely longer than the strip itself:

Under-cabinet light – cramped power plug

The OEM straight-on coaxial plug (near the bottom of the picture) attached to the wall wart cable obviously wouldn’t fit in the available space, so I gimmicked up a right-angle adapter by the simple expedient of shortening the solder lugs of a plug from the heap (which, admittedly, doesn’t quite fully seat in the socket), bending them sideways, soldering a pair of wires, heatshrinking appropriately, then coating wires + plug with JB Kwik epoxy. The other end of the wires gets a coaxial jack that miraculously fits the OEM plug, styled up with more heatshrink tubing. Not pretty, but nobody will ever see it.

Unlike the LED strip under the other cabinet, this IR proximity sensor doesn’t mind having a wood edge next to it and, thus, didn’t need a strip of tape to keep it happy.
2016-12-21

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:

Quilt block in scanner template

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:

Block 19

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

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:

Mary quilting

(*) 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
Left on Maloney Rd from Rt 376: Eyes Right!

We’re waiting for oncoming traffic to clear before making the left turn from Rt 376 onto Maloney, on our way to the rail trail:

Maloney Rd Intersection Conflict – 2016-12-07 – waiting

Traffic’s clear, we have the green, we’re turning, and the car exiting the gas station starts accelerating directly at us:

Maloney Rd Intersection Conflict – 2016-12-07 – turning

Mary shouts, I jam to a stop, the driver jams to a stop, I proceed, the driver then proceeds to turn in front of the truck behind us:

Maloney Rd Intersection Conflict – 2016-12-07 – rear view

There’s no signal aimed into the gas station, so you must use your best judgement to determine when to enter the intersection. I’m not in enough of a hurry to (try to) ace out a truck, but ya never know …

2016-12-18
Vista Point of Sale Terminal Boot Screen

Spotted this behind the Customer Service desk at the local movie theater (or whatever you call ’em these days):

Vista POS boot screen

I suppose those are the three things you do a lot of…

The next time we passed by, the screen displayed a more-or-less standard screensaver.

2016-12-17
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

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

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
Monthly Image: Red Squirrel

This red squirrel has the reddest tail of all:

Red squirrel on patio – front

Those white eye rings help carry off the whole “insufferably cute” thing:

Red squirrel on patio – side

We often see them scampering through the pine treee out back, where they pause to strip the seeds off unopened pine cones and toss the empties on the driveway.

Taken through two layers of wavy 1955-era glass with the Sony DSC-H5.

2016-12-15