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Archive for August, 2013

Survey Registration Number: Faceplant

A giant envelope containing one of those “political surveys” that’s actually a thinly disguised fundraiser arrived, with this confidence-inspiring ID in the upper-right corner:

Survey Registration Number

Survey Registration Number

The questions were all examples of false dichotomies.

A pox on their backsides, sez I.

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Why I Won’t Fix Your Windows PC

Got a call from a friend who was having trouble getting BitDefender to accept its new license key, so I drove over; she’s at the top of a killer hill and I’d already biked my two dozen miles for the day. Solving that problem was straightforward, if you happen to know that they use “authorization” and “license” as synonyms and that you access the key entry dialog by clicking on a text field that doesn’t look at all clickable.

I should have declared victory and returned to the Basement Laboratory, but, no, I had to be a nice guy.

BitDefender kvetched that it had been 777 days since its last scan, so I set up some regularly scheduled scans and automagic updates for everything in sight; we agreed she’d just let the thing run overnight on Mondays to get all that done.

BitDefender also suggested a handful of critical Windows XP updates, plus the usual Adobe Flash and Reader updates, plus some nonsense about Windows Live Messenger that seemed to require downloading and installing a metric shitload of Microsoft Bloatware. Rather than leave all that for next Monday’s unattended update, I unleashed the critical ones, did the Flash and Reader updates, and stuffed the Messenger update back under the rug.

Then AOL recommended an urgent update to AOL Desktop 9.7. She has a couple of AOL email addresses, mostly for historic reasons, and I asked if she ever used the AOL Desktop. She wasn’t sure, so I lit up the installed AOL Desktop 9.6: “Oh, that’s how I get all my email!” OK, so we’ll update that, too.

After all the thrashing was done, the system rebooted and presented us with the single most unhelpful error message I’ve ever seen:

Windows Error - Ordinal Not Found

Windows Error – Ordinal Not Found

No, you chowderheads, that is not OK…

Searching on the obvious terms indicated this had something to do with Internet Explorer 8 (remember IE 8?) and produced a number of irrelevant suggestions. The least awful seemed to involve running the Microsoft System File Checker utility:

sfc /scannow

Which I did.

It ran for the better part of an hour, then suggested a reboot. During the shutdown, it replaced 29 files at an average of about 5 minutes per file.

After which, Windows restarted and displayed exactly the same error message. Actually, a series of them; various programs couldn’t locate a fairly wide selection of ordinals in several DLLs.

OK. I give up.

We located a tech who does this sort of thing for a living. I’ve offered to split the cost of getting the box up and running again, with the understanding that it may be easier to start with a fresh off-lease Dell box running Windows 7 than to exhume an aging Windows XP installation.

I stopped caring about Windows toward the end of the last millennium and now keep a Token Windows Box only for hardware like the HOBOWare dataloggers and software like TurboTax.

Other than that, well…

I. Don’t. Care.

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Tour Easy: Another Kickstand Plate

I managed to lose another kickstand platesooo

Kickstand plate

Kickstand plate

The horrible paint crazing came from “priming” the bare plywood scrap (yes, that’s a stray hole from its previous life) with a specialty white paint intended for plastic lawn furniture; it apparently gets along poorly with the forget-me-not fluorescent red topcoat. Doesn’t matter in this application and uses up more of both rattlecans, so it’s all good.

Of course, after tucking it in the bike’s underseat bag, I spotted the lost plate along the DCRT: now I have a spare!

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Creating a Curvelicious Cookie Cutter

So, for reasons I need not go into, I needed an OpenSCAD solid model of a custom cookie cutter produced on an Afinia 3D printer from a Trimble Sketchup model:

Afinia Robot Cutter - on raft

Afinia Robot Cutter – on raft

The cutter is still attached to the raft that, it seems, is required for passable results on the Afinia’s platform.

Having already figured out how to wrap a cutter around a shape, the most straightforward procedure starts by extracting the cutter’s shape. So, lay the cutter face down on the scanner and pull an image into GIMP:

Afinia Robot - scan

Afinia Robot – scan

Blow out the contrast to eliminate the background clutter, then posterize to eliminate shadings:

Afinia Robot - scan enhanced

Afinia Robot – scan enhanced

Select the black interior region, grow the selection by a pixel or two, then shrink it back to eliminate (most of) the edge granularity, plunk it into a new image, and fill with black:

Afinia Robot - scan filled

Afinia Robot – scan filled

Now the magic happens…

Import the bitmap image into Inkscape. In principle, you can auto-trace the bitmap outline and clean it up manually, but a few iterations of that convinced me that it wasn’t worth the effort. Instead, I used Inkscape’s Bézier Curve tool to drop nodes (a.k.a. control points) at all the inflection points around the image, then warped the curves to match the outline:

Afinia Robot - Bezier spline fitting

Afinia Robot – Bezier spline fitting

If you’re doing that by hand, you could start with the original scanned image, but the auto-trace function works best with a high-contrast image and, after you give up on auto-tracing, you’ll find it’s easier to hand-trace a high-contrast image.

Anyhow, the end result of all that is a smooth path around the outline of the shape, without all the gritty details of the pixelated version. Save it as an Inkscape SVG file for later reference.

OpenSCAD can import a painfully limited subset of DXF files that, it seems, the most recent versions of Inkscape cannot produce (that formerly helpful tutorial being long out of date). Instead, I exported (using “Save as”) the path from Inkscape to an Encapsulated Postscript file (this is a PNG, as WordPress doesn’t show EPS files):

Afinia Robot - Bezier Curves.eps

Afinia Robot – Bezier Curves.eps

It’s not clear what the EPS file contains; I think it’s just a list of points around the path that doesn’t include the smooth Bézier goodness. That may account for the grittiness of the next step, wherein the pstoedit utility converts the EPS file into a usable DXF file:

pstoedit dxf:-polyaslines Afinia\ Robot\ -\ Bezier\ Curves.eps Afinia\ Robot\ -\ outline.dxf

Unfortunately, either the EPS file doesn’t have enough points on each curve or pstoedit automatically sets the number of points and doesn’t provide an override: contrary to what you (well, I) might think, the -splineprecision option doesn’t apply to whatever is in the EPS file. In any event, the resulting DXF file has rather low-res curves, but they were good enough for my purposes and OpenSCAD inhaled the DXF and emitted a suitable STL file:

Afinia Robot - shape slab

Afinia Robot – shape slab

To do that, you set the Layout variable to “Slab”, compile the model, and export the STL.

Being interested only in the process and its results, not actually cutting and baking cookies, I tweaked the OpenSCAD parameters to produce stumpy “cutters”:

Afinia Robot - solid model

Afinia Robot – solid model

You do that by setting the Layout variable to “Build”, compile the model, and export yet another STL. In the past, this seemed to be a less fragile route than directly importing and converting the DXF at each stage, but that may not be relevant these days. In any event, having an STL model of the cookie may be useful in other contexts, so it’s not entirely wasted effort.

Run the STL through Slic3r to get the G-Code as usual.

The resulting model printed in about 20 minutes apiece on the M2:

Robot Cutter - stumpy version

Robot Cutter – stumpy version

As it turns out, the fact that the M2 can produce ready-to-use cutters, minus the raft, is a strong selling point.

Given a workable model, the next step was to figure out the smallest possible two-thread-wide cutter blade, then run variations of the Extrusion Factor to see how that affected surface finish. More on that in a while.

The OpenSCAD source isn’t much changed from the original Tux Cutter; the DXF import required different scale factors:

// Robot cookie cutter using Minkowski sum
// Ed Nisley KE4ZNU - Sept 2011
// August 2013 adapted from the Tux Cutter

Layout = "Build";				// Build Slab

//- Extrusion parameters - must match reality!

ThreadThick = 0.25;
ThreadWidth = 0.40;

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

MaxSize = 150;				// larger than any possible dimension ...

Protrusion = 0.1;

//- Cookie cutter parameters

Size = 95;

TipHeight = IntegerMultiple(3.0,ThreadThick);
TipThick = 1.5*ThreadWidth;			// 1.5* = thinnest 2-thread wall, 1.0* thread has gaps

WallHeight = IntegerMultiple(1.0,ThreadThick);
WallThick = 4.5*ThreadWidth;

LipHeight = IntegerMultiple(1.0,ThreadWidth);
LipThick = IntegerMultiple(5,ThreadWidth);

//- Wrapper for the shape of your choice

module Shape(Size) {
  Robot(Size);
}

//- A solid slab of Tux goodness in simple STL format
// Choose magic values to:
//		center it in XY
//		reversed across Y axis (prints with handle on bottom)
//		bottom on Z=0
//		make it MaxSize from head to feet

module Tux(Scale) {
  STLscale = 250;
  scale(Scale/STLscale)
	translate([105,-145,0])
	  scale([-1,1,24])
		import(
		  file = "/mnt/bulkdata/Project Files/Thing-O-Matic/Tux Cookie Cutter/Tux Plate.stl",
		  convexity=5);
}

module Robot(Scale) {
    STLscale = 100.0;
    scale(Scale / STLscale)
			scale([-1,1,10])
				import("/mnt/bulkdata/Project Files/Thing-O-Matic/Pinkie/M2 Challenge/Afinia Robot.stl",
					convexity=10);
}

//- Given a Shape(), return enlarged slab of given thickness

module EnlargeSlab(Scale, WallThick, SlabThick) {

	intersection() {
	  translate([0,0,SlabThick/2])
		cube([MaxSize,MaxSize,SlabThick],center=true);
	  minkowski(convexity=5) {
		Shape(Scale);
		cylinder(r=WallThick,h=MaxSize,$fn=16);
	  }
	}

}

//- Put peg grid on build surface

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  RangeX = floor(100 / Space);
  RangeY = floor(125 / Space);

	for (x=[-RangeX:RangeX])
	  for (y=[-RangeY:RangeY])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

//- Build it

ShowPegGrid();

if (Layout == "Slab")
	Shape(Size);

if (Layout == "Build")
	difference() {
	union() {
		translate([0,0,(WallHeight + LipHeight - Protrusion)])
		EnlargeSlab(Size,TipThick,TipHeight + Protrusion);
		translate([0,0,(LipHeight - Protrusion)])
		EnlargeSlab(Size,WallThick,(WallHeight + Protrusion));
		EnlargeSlab(Size,LipThick,LipHeight);
	}
	Shape(Size);					// punch out cookie hole
	}

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Soldering Project: Astable Multivibrator

We’ve been kicking around ideas for introductory soldering / electronics projects at Squidwrench, which prompted me to come up with a classic astable multivibrator circuit:

Astable Multivibrator - simulation

Astable Multivibrator – simulation

Everything is totally non-critical: it should oscillate as long as the base resistors are small enough to lightly saturate the transistors. The LEDs let you know it’s actually working.

You’d probably want a few decades of caps and a decade’s worth of resistors on pin headers, so as to cover the range from visible blinkiness to nasty audio squeal.

The pulse generator and cap at the bottom apply a jolt at T=0 to knock the circuit off balance. Otherwise, the simulation will just sit there and do nothing; in the real world, of course, nothing stays balanced for very long.

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Basement Safe: Foam Door Seal

A bit of rummaging in the Big Box o’ Weatherstripping produced the stub end of a spool bearing 1/4 x 1/8 foam tape that exactly fills the gap between the Basement Safe’s door and liner:

Basement Safe - Foam door seal - latch side

Basement Safe – Foam door seal – latch side

The hinge side of the door has tape between the door liner and the safe wall, because that closes in compression rather than shear:

Basement Safe - Foam door seal - hinge side

Basement Safe – Foam door seal – hinge side

There should be a big bump in the humidity record marking that installation, but I don’t expect any immediate difference. If the silica gel lasts more than two months, I’ll consider it a win.

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Giant Swallowtail Butterfly: Up and Away!

The Giant Swallowtails once again returned to the Butterfly Bush at the front window this year:

Giant Swallowtail - Liftoff

Giant Swallowtail – Liftoff

Their wings never stop fluttering while they feed:

Giant Swallowtail - feeding

Giant Swallowtail – feeding

I’ve never seen butterfly wings in this position:

Giant Swallowtail - Downstroke

Giant Swallowtail – Downstroke

All hand-held with the Sony DSC-H5 and no additional lenses. The top picture was underexposed by two stops to remove the background. The bottom picture has fill flash in addition to full sun backlight.

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