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.

Tag: Improvements

Making the world a better place, one piece at a time

Tektronix Circuit Computer: Layout Analysis
Following a linkie I can no longer find led me to retrieve the Tektronix Circuit Computer in my Box o’ Slide Rules:

Tektronix Circuit Computer – front

I’m pretty sure it came from Mad Phil’s collection. One can line up the discolored parts of the decks under their cutout windows to restore it to its previous alignment; most likely it sat at the end of a row of books (remember books?) on his reference shelf.

The reverse side lists the equations it can solve, plus pictorial help for the puzzled:

Tektronix Circuit Computer – rear

Some searching reveals the original version had three aluminum disks, shaped and milled and photo-printed, with a honkin’ hex nut holding the cursor in place. The one I have seems like laser-printed card stock between plastic laminating film; they don’t make ’em like that any more, either.

TEK PN 003-023 (the paper edition) runs about thirty bucks (modulo the occasional outlier) on eBay, so we’re not dealing in priceless antiquity here. The manual is readily available as a PDF, with photos in the back.

Some doodling produced key measurements:

Tektronix Circuit Computer – angle layout

All the dimensions are hard inches, of course.

Each log decade spans 18°, with the Inductive Frequency scale at 36° for the square root required to calculate circuit resonance.

Generating the log scales requires handling all possible combinations of:
- Scales increase clockwise
- Scales increase counterclockwise
- Ticks point outward
- Ticks point inward
- Text reads from center
- Text reads from rim
I used the 1×10⁰ tick on the outer scale of each deck as the 0° reference for the other scales on that deck. The 0° tick appears at the far right of plots & engravings & suchlike.

The L/R Time Constant (tau = τ) pointer on the top deck and the corresponding τL scale on the bottom deck has (what seems like) an arbitrary -150° offset from the 0° reference.

The Inductive Frequency scale has an offset of 2π, the log of which is 0.79818 = 14.37°.

The risetime calculations have a factor of 2.197, offsetting those pointers from their corresponding τ pointer by 0.342 = log(2.197) = 6.15°.

A fair bit of effort produced a GCMC program creating a full-size check plot of the bottom deck on the MPCNC:

Tektronix Circuit Computer – Bottom Deck – scale check plot

By the conservation of perversity, the image is rotated 90° to put the 1 H tick straight up.

The 3018 can’t handle a 7.75 inch = 196 mm disk, but a CD-size (120 mm OD) engraving came out OK on white plastic filled with black crayon:

Tek CC bottom – ABS 160g 2400mm-min

The millimeter scale over on the right shows the letters stand a bit under 1 mm tall. And, yes, the middle scale should read upside-down.

Properly filling the engraved lines remains an ongoing experiment. More downforce on the diamond or more passes through the G-Code should produce deeper trenches, perhaps with correspondingly higher ridges along the sides. Sanding & polishing the plastic without removing the ink seems tedious.

The Great Dragorn of Kismet observes I have a gift for picking projects at the cutting edge of consumer demand.

More doodles while figuring the GCMC code produced a summary of the scale offsets:

Tektronix Circuit Computer – scale angle tabulation

Musings on the parameters of each scale:

Tektronix Circuit Computer – scale parameters

How to draw decades of tick marks:

Tektronix Circuit Computer – decade tick doodles

It turned out easier to build vectors of tick mark values and their corresponding lengths, with another list of ticks to be labeled, than to figure out how to automate those values.

More on all this to come …
2019-11-22
Soundbar Power

A Dell soundbar under the landscape monitor suffices for my simple audio needs, and, when the Dell U2711 went toes-up, I conjured a 12 V wart from the heap. A recent cleanup made a smaller wart available, but required mating two coaxial plugs:

Coax power plugs – brass tube connector

A snippet of brass tube suffices for the center pin. The outer shell is a larger brass tube, slit lengthwise, trimmed to fit the plug circumference and rolled around a smaller drill bit to make it springy in the right direction.

A wrap of silicone tape and it’s all good:

Dell Sound Bar power splice

Ugly, but good.

2019-11-20

CNC 3018-Pro: Collet Pen Holder

Along the same lines as the MPCNC pen holder, I now have one for the 3018:

CNC3018 - Collet pen holder - assembled — CNC3018 – Collet pen holder – assembled

The body happened to be slightly longer than two LM12UU linear bearings stacked end-to-end, which I didn’t realize must be a constraint until I was pressing them into place:

CNC 3018-Pro Collet Holder - LM12UU - solid model — CNC 3018-Pro Collet Holder – LM12UU – solid model

In the unlikely event I need another one, the code will sprout a max() function in the appropriate spot.

Drilling the aluminum rod for the knurled ring produced a really nice chip:

CNC3018 - Collet pen holder - drilling knurled ring — CNC3018 – Collet pen holder – drilling knurled ring

Yeah, a good drill will produce two chips, but I’ll take what I can get.

There’s not much left of the original holder after turning it down to 8 mm so it fits inside the 12 mm rod:

CNC3018 - Collet pen holder - turning collet OD — CNC3018 – Collet pen holder – turning collet OD

Confronted by so much shiny aluminum, I realized I didn’t need an 8 mm hole through the rod, so I cut off the collet shaft and drilled out the back end to clear the flanges on the ink tubes:

CNC3018 - Collet pen holder - drilling out collet — CNC3018 – Collet pen holder – drilling out collet

I figured things would eventually go badly if I trimmed enough ink-filled crimps:

Collet holder - pen cartridge locating flanges — Collet holder – pen cartridge locating flanges

The OpenSCAD source code as a GitHub Gist:

	// Collet Pen Holder in LM12UU linear bearings for CNC3018
	// Ed Nisley KE4ZNU – 2019-10-30

	Layout = "Build"; // [Build, Show, Base, Mount, Plate]

	/* [Hidden] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 0.40; // [0.40, 0.40]

	/* [Hidden] */

	Protrusion = 0.1; // [0.01, 0.1]

	HoleWindage = 0.2;

	inch = 25.4;

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

	ID = 0;
	OD = 1;
	LENGTH = 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);
	}

	//- Dimensions

	PenOD = 3.5; // pen cartridge diameter

	Bearing = [12.0,21.0,30.0]; // linear bearing body

	SpringSeat = [0.56,10.0,3*ThreadThick]; // wire = ID, coil = OD, seat depth = length

	WallThick = 4.0; // minimum thickness / width

	Screw = [3.0,6.75,25.0]; // holding it all together, OD = washer

	Insert = [3.0,5.5,8.2]; // brass insert
	//Insert = [4.0,6.0,10.0];

	Clamp = [43.2,44.5,34.0]; // tool clamp ring, OD = clearance around top

	LipHeight = IntegerMultiple(2.0,ThreadThick); // above clamp for retaining

	BottomExtension = 25.0; // below clamp to reach workpiece

	MountOAL = LipHeight + Clamp[LENGTH] + BottomExtension; // total mount length
	echo(str("Mount OAL: ",MountOAL));

	Plate = [1.5PenOD,Clamp[ID] – 02*WallThick,WallThick]; // spring reaction plate

	NumScrews = 3;
	ScrewBCD = Bearing[OD] + Insert[OD] + 2*WallThick;

	echo(str("Retainer max OD: ",ScrewBCD – Screw[OD]));

	NumSides = 9*4; // cylinder facets (multiple of 3 for lathe trimming)

	// Basic mount shape

	module CNC3018Base() {

	translate([0,0,MountOAL – LipHeight])
	cylinder(d=Clamp[OD],h=LipHeight,$fn=NumSides);
	translate([0,0,MountOAL – LipHeight – Clamp[LENGTH] – Protrusion])
	cylinder(d=Clamp[ID],h=(Clamp[LENGTH] + 2*Protrusion),$fn=NumSides);
	cylinder(d1=Bearing[OD] + 2*WallThick,d2=Clamp[ID],h=BottomExtension + Protrusion,$fn=NumSides);

	}

	// Mount with holes & c

	module Mount() {

	difference() {
	CNC3018Base();

	translate([0,0,-Protrusion]) // bearing
	PolyCyl(Bearing[OD],2*MountOAL,NumSides);

	for (i=[0:NumScrews – 1]) // clamp screws
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,MountOAL – Clamp[LENGTH]])
	rotate(180/8)
	PolyCyl(Insert[OD],Clamp[LENGTH] + Protrusion,8);
	}

	}

	module SpringPlate() {

	difference() {
	cylinder(d=Plate[OD],h=Plate[LENGTH],$fn=NumSides);

	translate([0,0,-Protrusion])
	PolyCyl(Plate[ID],2*MountOAL,NumSides);

	translate([0,0,Plate.z – SpringSeat[LENGTH]]) // spring retaining recess
	PolyCyl(SpringSeat[OD],SpringSeat[LENGTH] + Protrusion,NumSides);

	for (i=[0:NumScrews – 1]) // clamp screws
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,-Protrusion])
	rotate(180/8)
	PolyCyl(Screw[ID],2*MountOAL,8);
	}

	}


	//—–
	// Build it

	if (Layout == "Base")
	CNC3018Base();

	if (Layout == "Mount")
	Mount();

	if (Layout == "Plate")
	SpringPlate();

	if (Layout == "Show") {
	Mount();
	translate([0,0,1.25*MountOAL])
	rotate([180,0,0])
	SpringPlate();
	}

	if (Layout == "Build") {

	translate([0,-0.75*Clamp[OD],MountOAL])
	rotate([180,0,0])
	Mount();
	translate([0,0.75*Plate[OD],0])
	SpringPlate();
	}

view raw CNC 3018-Pro Collet Holder – LM12UU.scad hosted with ❤ by GitHub

2019-11-18

Monthly Science: Weight

After another two months:

Weight Chart 2019-10 – Ed

The trend is definitely not uniformly downward, perhaps due to my increasing ability to accelerate (small) masses against the local gravity vector and, definitely, garden harvest season. My pants still fit fine, if that’s any indication.

I’ll add a skin-fold caliper dot to the weekly record after I can get repeatable measurements, perhaps by marking the test spot with a Sharpie.

2019-11-01
ID3 Tagging From File Names
The Forester can play MP3 files from a USB flash drive and, given the utter craptitude of radio stations around here, I dumped a bunch of CD tracks onto a drive. For historic reasons, very few of the tracks had ID3 tags, so the Forester’s display showed only gnarly file names for the last few years.

This burst of Bash line noise runs through the directory of album directories, extracts the relevant information from the directory and track names, then pops the tags in place:
```
for d in * ; do for f in $(ls $d) ; do art=$(echo $d | cut -d- -f1 | tr '_' ' ' | sed 's/-/ - /g') ; alb=$(echo $d | cut --complement -d- -f1 | tr '_' ' ' | sed 's/-/ - /g') ; t=$(echo $f | cut -d- -f1) ; s=$(echo ${f%.*} | cut --complement -d- -f1 | tr '_' ' ' | sed 's/-/ - /g') ; id3tag -2 -a"$art" -A"$alb" -s"$s" -t$t $d/$f ; done ; done
```
It’s (marginally) easier to see this way:
```
for d in * ; do 
 for f in $(ls $d) ; do 
  art=$(echo $d | cut -d- -f1 | tr '_' ' ' | sed 's/-/ - /g')
  alb=$(echo $d | cut --complement -d- -f1 | tr '_' ' ' | sed 's/-/ - /g')
  t=$(echo $f | cut -d- -f1)
  s=$(echo ${f%.*} | cut --complement -d- -f1 | tr '_' ' ' | sed 's/-/ - /g')
  id3tag -2 -a"$art" -A"$alb" -s"$s" -t$t $d/$f
 done
done
```
What’s going on:
- cut – extracts track number and song title
- tr – convert underscores to spaces
- sed – put spaces around hyphens
The id3tag program can install either ID3V1 or ID3V2 tags on each pass, so I just recalled the command, edited the -1 to -2, and ran the whole mess again.

After a bit of manual cleanup, things looked pretty good.

Although the id3ren program seemed as though it could do the trick, it’s really intended to rename files from existing tags. Making it go the other way rapidly became a steel-cage death match; I gave up.
2019-10-28
Manjaro Linux VNC Setup

I installed the XFCE flavor of Manjaro Linux (beside Win 8.1 Pro) on a new-to-me Dell Latitude 7250 serving as our new Token Windows box and carry-along-able Linux laptop.

Manjaro being an offshoot of Arch, they have plenty of guides and references, with How to Set up X11VNC Server being most useful at the moment. This box needs only a VNC server and apparently works with ‑xdamage for faster updates.

With the laptop plugged into an external display and Manjaro set up to use both displays, the X11VNC server feeds both to the client with the proper positioning, producing a truly panoramic, albeit scaled, view:

WinFlip – X11VNC dual screen

TightVNC on Windows does much the same thing, although (AFAICT) Windows doesn’t allow different background pictures on the two screens; that’s irrelevant to my mmmm use case.

2019-10-23
Monthly Image: Spider vs. Marmorated Stink Bug

Fortunately, Brown Marmorated Stink Bugs haven’t been as catastrophic as predicted when they arrived a few years ago, perhaps because native critters have learned to deal with them:

Spider vs. Marmorated Stink Bug

Looks like a week’s worth of spider chow!

2019-10-15

Tag: Improvements

Tektronix Circuit Computer: Layout Analysis

Soundbar Power

CNC 3018-Pro: Collet Pen Holder

Monthly Science: Weight

ID3 Tagging From File Names

Manjaro Linux VNC Setup

Monthly Image: Spider vs. Marmorated Stink Bug