Software – Page 57 – The Smell of Molten Projects in the Morning

Rubber Soaker Hose Repair

A soaker hose leaped under a descending garden fork and accumulated a nasty gash:

Soaker Hose Splice - gashed — Soaker Hose Splice – gashed

Mary deployed a spare and continued the mission, while I pondered how to fix such an odd shape.

For lack of anything smarter, I decided to put a form-fitting clamp around the hose, with silicone caulk buttered around the gash to (ideally) slow down any leakage:

Soaker Hose Splice - Solid Model - Assembled — Soaker Hose Splice – Solid Model – Assembled

As usual, some doodling got the solid model started:

Soaker Hose Splice - Dimension doodle 1 — Soaker Hose Splice – Dimension doodle 1

A hose formed from chopped rubber doesn’t really have consistent dimensions, so I set up the model to spit out small test pieces:

Soaker Hose Splice - Test Fit - Slic3r — Soaker Hose Splice – Test Fit – Slic3r

Lots and lots of test pieces:

Soaker Hose Splice - test pieces — Soaker Hose Splice – test pieces

Each iteration produced a better fit, although the dimensions never really converged:

Soaker Hose Splice - Dimension doodle 2 — Soaker Hose Splice – Dimension doodle 2

The overall model looks about like you’d expect:

Soaker Hose Splice - Complete - Slic3r — Soaker Hose Splice – Complete – Slic3r

The clamp must hold its shape around a hose carrying 100 psi (for real!) water, so I put 100 mil aluminum backing plates on either side. Were you doing this for real, you’d shape the plates with a CNC mill, but I just bandsawed them to about the right size and transfer-punched the hole positions:

Soaker Hose Splice - plate transfer punch — Soaker Hose Splice – plate transfer punch

Some drill press action with a slightly oversize drill compensated for any misalignment and Mr Disk Sander rounded the corners to match the plastic block:

Soaker Hose Splice - plate corner rounding — Soaker Hose Splice – plate corner rounding

A handful of stainless steel 8-32 screws holds the whole mess together:

Soaker Hose Splice - installed — Soaker Hose Splice – installed

These hoses spend their lives at rest under a layer of mulch, so I’m ignoring the entire problem of stress relief at those sharp block edges. We’ll see how this plays out in real life, probably next year.

I haven’t tested it under pressure, but it sure looks capable!

The OpenSCAD source code as a GitHub Gist:

	// Rubber Soaker Hose Splice
	// Ed Nisley KE4ZNU July 2018

	Layout = "Build"; // Hose Block Show Build

	TestFit = false; // true to build test fit slice from center

	//- 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
	// Hose lies along X axis

	Hose = [200,27.0,12.0]; // X = longer than anything else

	Block = [80.0,50.0,4.0 + Hose.z]; // overall splice block size
	echo(str("Block: ",Block));

	Kerf = 0.1; // cut through middle to apply compression

	ID = 0;
	OD = 1;
	LENGTH = 2;

	// 8-32 stainless screws
	Screw = [4.1,8.0,3.0]; // OD = head LENGTH = head thickness
	Washer = [4.4,9.5,1.0];
	Nut = [4.1,9.7,6.0];

	CornerRadius = Washer[OD]/2;

	NumScrews = 3; // screws along each side of cable
	ScrewOC = [(Block.x – 2*CornerRadius) / (NumScrews – 1),
	Block.y – 2*CornerRadius,
	2*Block.z // ensure complete holes
	];

	echo(str("Screw OC: x=",ScrewOC.x," y=",ScrewOC.y));

	//———————-
	// 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);
	}

	// Hose shape
	// This includes magic numbers measured from reality

	module HoseProfile() {

	RimThick = 10.0; // outer sections
	RimOD = RimThick;
	RimFlatRecess = -0.7; // recess to front flat surface

	OuterOC = Hose.y – RimOD; // outer tube centers

	RecessM = 1.5; // back recess chord
	RecessC = OuterOC;
	RecessR = (pow(RecessM,2) + pow(RecessC,2)/4) / (2*RecessM);

	RidgeM = 1.0; // front ridge chord
	RidgeC = 8.0;
	RidgeR = (pow(RidgeM,2) + pow(RidgeC,2)/4) / (2*RidgeM);

	NumSides = 12*4;

	rotate([0,-90,0])
	translate([0,0,-Hose.x/2])
	linear_extrude(height=Hose.x,convexity=4)
	difference() {
	union() {
	for (j=[-1,1]) // outer channels
	translate([0,j*OuterOC/2])
	circle(d=RimOD,$fn=NumSides);
	translate([-RimOD/4,0]) // rear flat fill
	square([RimOD/2,OuterOC],center=true);
	translate([(RimOD/4 + RimFlatRecess),0]) // front flat fill
	square([RimOD/2,OuterOC],center=true);
	intersection() {
	translate([Hose.z/2,0])
	square([Hose.z,OuterOC],center=true);
	translate([-RidgeR + RimOD/2 + RimFlatRecess + RidgeM,0])
	circle(r=RidgeR,$fn=NumSides);
	}
	}
	translate([-(RecessR + RimOD/2 – RecessM),0])
	circle(r=RecessR,$fn=2*NumSides);
	}
	}

	// Outside shape of splice Block
	// Z centered on hose rim circles, not overall thickness through center ridge

	module SpliceBlock() {
	difference() {
	hull()
	for (i=[-1,1], j=[-1,1]) // rounded block
	translate([i(Block.x/2 – CornerRadius),j(Block.y/2 – CornerRadius),-Block.z/2])
	cylinder(r=CornerRadius,h=Block.z,$fn=4*8);
	for (i = [0:NumScrews – 1], j=[-1,1]) // screw holes
	translate([-(Block.x/2 – CornerRadius) + i*ScrewOC.x,
	j*ScrewOC.y/2,
	-(Block.z/2 + Protrusion)])
	PolyCyl(Screw[ID],Block.z + 2*Protrusion,6);
	cube([2Block.x,2Block.y,Kerf],center=true); // slice through center
	}
	}

	// Splice block less hose

	module ShapedBlock() {
	difference() {
	SpliceBlock();
	HoseProfile();
	}
	}




	//———-
	// Build them

	if (Layout == "Hose")
	HoseProfile();

	if (Layout == "Block")
	SpliceBlock();

	if (Layout == "Bottom")
	BottomPlate();

	if (Layout == "Top")
	TopPlate();

	if (Layout == "Show") {
	difference() {
	SpliceBlock();
	HoseProfile();
	}
	color("Green",0.25)
	HoseProfile();
	}

	if (Layout == "Build") {
	SliceOffset = TestFit && !NumScrews%2 ? ScrewOC.x/2 : 0;
	intersection() {
	translate([SliceOffset,0,Block.z/4])
	if (TestFit)
	cube([ScrewOC.x/2,4*Block.y,Block.z/2],center=true);
	else
	cube([4Block.x,4Block.y,Block.z/2],center=true);
	union() {
	translate([0,0.6*Block.y,Block.z/2])
	ShapedBlock();
	translate([0,-0.6*Block.y,Block.z/2])
	rotate([0,180,0])
	ShapedBlock();
	}
	}
	}

view raw Soaker Hose Splice.scad hosted with ❤ by GitHub

2018-07-25

Tour Easy Front Fender Clip: Longer and Stronger

We negotiated the Belmar Bridge ~~connection~~ stairway from the Allegheny River Trail to the Sandy Creek trail:

Belmar Bridge Stairs - Overview — Belmar Bridge Stairs – Overview

We’re maneuvering Mary’s bike, but you get the general idea. Our bikes aren’t built for stairways, particularly ones with low overheads:

Belmar Bridge Stairs - Low Overhead — Belmar Bridge Stairs – Low Overhead

The front fender clip on my Tour Easy snapped (at the expected spots) when the mudflap snagged on one of the angles:

Belmar Bridge Stairs - First Turn — Belmar Bridge Stairs – First Turn

For some inexplicable reason, I didn’t have a roll of duct tape in my packs, so the temporary repair required a strip of tape from a battery pack, two snippets of hook-and-loop tape, and considerable muttering:

Tour Easy front fender clip - expedient repair — Tour Easy front fender clip – expedient repair

It was good for two dozen more miles to the end of our vacation, so I’d say that was Good Enough.

The new version has holes in the ferrules ten stay diameters deep, instead of six, which might eliminate the need for heatstink tubing. I added a small hole at the joint between the curved hooks and the ferrules to force more plastic into those spots:

Front Fender Clip - Slic3r — Front Fender Clip – Slic3r

I also bent the hanger extension to put the fender’s neutral position closer to the wheel.

We’ll see how long this one lasts. By now, I now have black double-sticky foam tape!

The OpenSCAD source code as a GitHub Gist:

	// Tour Easy front fender clip
	// Ed Nisley KE4ZNU July 2017

	Layout = "Build"; // Build Profile Ferrule Clip

	//- 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

	// special case: fender is exactly half a circle!

	FenderC = 51.0; // fender outside width = chord
	FenderM = 21.0; // height of chord

	FenderR = (pow(FenderM,2) + pow(FenderC,2)/4) / (2 * FenderM); // radius
	echo(str("Fender radius: ", FenderR));
	FenderD = 2*FenderR;

	FenderA = 2 * asin(FenderC / (2*FenderR));
	echo(str(" … Arc: ",FenderA," deg"));

	FenderThick = 2.5; // fender thickness, assume dia of edge

	ClipHeight = 15.0; // top to bottom, ignoring rakish tilt
	ClipThick = IntegerMultiple(2.5,ThreadWidth); // thickness of clip around fender
	ClipD = FenderD; // ID of clip against fender
	ClipSides = 4 * 8; // polygon sides around clip circle

	BendReliefD = 2.5; // bend arch diameter
	BendReliefA = 2/3 * FenderA/2; // … angle from dead ahead
	BendReliefCut = 1.5; // factor to thin outside of bend

	ID = 0;
	OD = 1;
	LENGTH = 2;

	StayDia = 3.3; // fender stay rod diameter
	StayOffset = 15.0; // stay-to-fender distance
	StayPitch = -5; // angle from stay to fender arch

	DropoutSpace = 120; // stay spacing at wheel hub
	StayLength = 235; // stay length: hub to fender
	StaySplay = asin((DropoutSpace – FenderC)/(2*StayLength)); // outward angle to hub

	echo(str(" … Pitch: ",StayPitch," deg"));
	echo(str(" … Splay: ",StaySplay," deg"));

	FerruleSides = 2*4;
	Ferrule = [StayDia,3FenderThick/cos(180/FerruleSides),10StayDia + StayOffset]; // ID = stay rod OD
	FerruleHoleD = 0.1; // small hole to create solid plastic at ferrule joint

	//———————-
	// 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(r=(FixDia + HoleWindage)/2,
	h=Height,
	$fn=Sides);
	}

	//———————-
	// Clip profile around fender
	// Centered on fender arc

	module Profile(HeightScale = 1) {

	linear_extrude(height=HeightScale*ClipHeight,convexity=5) {
	difference() {
	offset(r=ClipThick) // outside of clip
	union() {
	circle(d=ClipD,$fn=ClipSides);
	for (i=[-1,1])
	rotate(i*BendReliefA) {
	translate([ClipD/2 + BendReliefD/2,0,0])
	circle(d=BendReliefD,$fn=6);
	}
	}
	union() { // inside of clip
	circle(d=ClipD,$fn=ClipSides);
	for (i=[-1,1])
	rotate(i*BendReliefA) {
	translate([ClipD/2 + BendReliefCut*BendReliefD/2,0,0])
	circle(d=BendReliefD/cos(180/6),$fn=6);
	translate([ClipD/2,0,0])
	square([BendReliefCut*BendReliefD,BendReliefD],center=true);
	}
	}
	translate([(FenderR – FenderM – FenderD/2),0]) // trim ends
	square([FenderD,2*FenderD],center=true);
	}

	for (a=[-1,1]) // hooks around fender
	rotate(a*(FenderA/2))
	translate([FenderR – FenderThick/2,0]) {
	difference() {
	rotate(1*180/12)
	circle(d=FenderThick + 2*ClipThick,$fn=12);
	rotate(1*180/8)
	circle(d=FenderThick,$fn=8);
	rotate(a * -90)
	translate([0,-2*FenderThick,0])
	square(4*FenderThick,center=false);
	}
	}
	}
	}


	//———————-
	// Ferrule body

	module FerruleBody() {

	translate([0,0,Ferrule[OD]/2 * cos(180/FerruleSides)])
	rotate([0,-90,0]) rotate(180/FerruleSides)
	difference() {
	cylinder(d=Ferrule[OD],h=Ferrule[LENGTH],$fn=FerruleSides,center=false);
	translate([0,0,StayOffset + Protrusion])
	PolyCyl(Ferrule[ID],Ferrule[LENGTH] – StayOffset + Protrusion,FerruleSides);

	}

	}

	//———————-
	// Generate entire clip at mounting angle

	module FenderClip() {

	difference() {
	union() {
	translate([FenderR,0,0])
	difference() { // angle and trim clip
	rotate([0,StayPitch,0])
	translate([-(FenderR + ClipThick),0,0])
	Profile(2); // scale upward for trimming
	translate([0,0,-ClipHeight]) // trim bottom
	cube(2*[FenderD,FenderD,ClipHeight],center=true);
	translate([0,0,ClipHeight*cos(StayPitch)+ClipHeight]) // trim top
	cube(2*[FenderD,FenderD,ClipHeight],center=true);
	}
	for (j = [-1,1]) // place ferrules
	translate([Ferrule[OD]sin(StayPitch) + (Ferrule[OD]/2)sin(StaySplay),j*(FenderR – FenderThick/2),0])
	rotate(-j*StaySplay)
	FerruleBody();
	}
	for (i=[-1,1]) // punch stiffening holes
	translate([FenderThick/2,-i*(FenderR – FenderThick/2),Ferrule[OD]/2])
	rotate([0,-90,i*StaySplay])
	PolyCyl(FerruleHoleD,Ferrule[OD],FerruleSides);

	}
	}

	//———————-
	// Build it


	if (Layout == "Profile") {
	Profile();
	}

	if (Layout == "Ferrule") {
	FerruleBody();
	}

	if (Layout == "Clip") {
	FenderClip();
	}

	if (Layout == "Build") {
	FenderClip();
	}

view raw Front Fender Clip.scad hosted with ❤ by GitHub

As a bonus for paging all the way to the end, here’s the descent on the same stairway:

Belmar Bridge Stairs - Descent — Belmar Bridge Stairs – Descent

No, I wasn’t even tempted …

2018-07-24

Copying Action Camera Video: Now With UUIDs

Having tired of manually decoding UDEV’s essentially random device names produced for the various USB action cameras and card readers, I put the device UUIDs in /etc/fstab and let the device names fall where they may:

UUID=B40C6DD40C6D9262	/mnt/video	ntfs	noauto,uid=ed 0 0
UUID=0FC4-01AB	/mnt/Fly6	vfat	noauto,nodiratime,uid=ed	0	0
UUID=0000-0001	/mnt/M20	vfat	noauto,nodiratime,uid=ed	0	0
LABEL=AS30V	/mnt/AS30V	exfat	noauto,nodiratime,uid=ed	0	0

You get those by plugging everything in, running blkid, and sorting out the results.

The 64 GB MicroSD card from the Sony AS30V camera uses Microsoft’s proprietary exfat file system, which apparently doesn’t associate a UUID/GUID with the entire device, so you must use a partition label. The Official SD Card Formatter doesn’t (let you) set one, so:

exfatlabel /dev/sdd1 AS30V

It turns out you can include spaces in the partition label, but there’s no way to escape them (that I know of) in /etc/fstab, so being succinct counts for more than being explanatory.

One could name the partition in the Windows device properties pane, which would make sense if one knew it was necessary while the Token Windows Laptop was booted with the card in place.

I think this is easier then trying to persuade UDEV to create known device names based on the USB hardware characteristics, because those will depend on which USB card / device / reader I use. I can force the UUIDs to be whatever I want, because they’re just bits in the disk image.

With all that in place, you plug in All. The. Gadgets. and run the script (as seen below). The general idea is to verify the bulk video drive mounted OK, attempt to mount each memory card and fire off a corresponding rsync copy, wait until they’re all done, tidy the target filenames, then delete all the source files to get ready for the next ride.

Funneling all three copies to a single USB hard drive probably isn’t the smartest thing, but the overall write ticks along at 18 MB/s, which is Good Enough for my simple needs. If the drive thrashes itself to death, I won’t do it again; I expect it won’t fail until well outside the 1 year limited warranty.

If any of the rsync copies fail, then nothing gets deleted. I’m a little queasy about automagically deleting files, but it’s really just video with very little value. Should something horrible happen, I’d do the copies by hand, taking great care to not screw up.

After all, how many pictures like this do we need?

The Bash script as a GitHub Gist:

	UUID=B40C6DD40C6D9262 /mnt/video ntfs noauto,uid=ed 0 0
	UUID=0FC4-01AB /mnt/Fly6 vfat noauto,nodiratime,uid=ed 0 0
	UUID=0000-0001 /mnt/M20 vfat noauto,nodiratime,uid=ed 0 0
	LABEL=AS30V /mnt/AS30V exfat noauto,nodiratime,uid=ed 0 0

view raw fstab hosted with ❤ by GitHub

	#!/bin/bash
	# This uses too many bashisms for dash

	thisdate=$(date –rfc-3339=date)
	echo Date is $thisdate
	date

	# MicroSD / readers / USB drive defined in fstab
	# … with UUID or PARTID as appropriate
	echo Mounting bulk video drive
	sudo mount /mnt/video
	if [ $? -ne 0 ]; then
	echo '** Cannot mount video storage drive'
	exit
	fi
	# Show starting space available
	df -h /mnt/video

	#– Sony AS30V
	printf "\n— AS30V\n"
	as30v=/mnt/AS30V
	sudo mount $as30v
	if [ $? -eq 0 ]; then
	echo " start AS30V transfer on $as30v"
	mkdir /mnt/video/AS30V/$thisdate
	rsync -ahu –progress –exclude "*THM" $as30v/MP_ROOT/100ANV01/ /mnt/video/AS30V/$thisdate &
	pid1=$!
	echo " PID is $pid1"
	else
	echo " skipping"
	as30v=
	fi

	#– Cycliq Fly6
	printf "\n— Fly6\n"
	fly6=/mnt/Fly6
	sudo mount $fly6
	if [ $? -eq 0 ]; then
	echo " start Fly6 transfer on $fly6"
	rsync -ahu –progress $fly6 /mnt/video &
	pid2=$!
	echo " PID is $pid2"
	else
	echo " skipping"
	fly6=
	fi

	#– SJCAM M20
	printf "\n— M20\n"
	m20=/mnt/M20
	sudo mount $m20
	if [ $? -eq 0 ]; then
	echo " start M20 transfer on $m20"
	mkdir /mnt/video/M20/$thisdate
	# See if any still images exist to avoid error messages
	n=$( ls $m20/DCIM/Photo/* 2> /dev/null \| wc -l )
	if [ $n -gt 0 ] ; then
	echo " copy M20 photos first"
	rsync -ahu –progress $m20/DCIM/Photo/ /mnt/video/M20/$thisdate
	fi
	rsync -ahu –progress $m20/DCIM/Movie/ /mnt/video/M20/$thisdate &
	pid3=$!
	echo " PID is $pid3"
	else
	echo " skipping"
	m20=
	fi

	printf "\n—– Waiting for all rsync terminations\n"
	rc=0
	for p in $pid1 $pid2 $pid3 ; do
	wait -n
	rc=$(( rc+$? ))
	echo RC so far: $rc
	done
	date

	if [ $rc -eq 0 ] ; then
	echo '—– Final cleanups'
	echo Fix capitalized extensions
	find /mnt/video -name \*AVI -print0 \| xargs -0 rename -v -f 's/AVI/avi/'
	find /mnt/video -name \*MP4 -print0 \| xargs -0 rename -v -f 's/MP4/mp4/'

	if [ "$as30v" ]; then
	echo Remove files on $as30v
	rm $as30v/MP_ROOT/100ANV01/*
	sudo umount $as30v
	fi

	if [ "$fly6" ]; then
	echo Remove files on $fly6
	rm -rf $fly6/DCIM/*
	sudo umount $fly6
	fi

	if [ "$m20" ]; then
	echo Remove files on $m20
	rm $m20/DCIM/Movie/* $m20/DCIM/Photo/*
	sudo umount $m20
	fi

	echo '—– Space remaining on video drive'
	df -h /mnt/video
	sudo umount /mnt/video
	echo Done!
	else
	echo Whoopsie! Total RC: $rc
	fi

view raw savevideo.sh hosted with ❤ by GitHub

2018-07-17

Xubuntu 18.04 vs. VNC

For unknown reasons, the Gnome-ish vino-server package for Xubuntu 18.04 no longer installs vino-preferences, so it’s not obvious how to configure the server.

After considerable flailing, I installed good old x11vnc, set up a password, then started it in .xprofile:

x11vnc -forever -find -no6 -avahi -usepw

I don’t mind having programs change, but it’d be nice if features like, say, configuration wouldn’t just vanish.

2018-06-27

Tour Easy Front Derailleur Cable Clamp

In addition to sawing through the side of the cable ferrule, the front derailleur cable began breaking at the edge of the derailleur arm:

Tour Easy Front Derailleur Cable - frayed — Tour Easy Front Derailleur Cable – frayed

It wouldn’t have survived another ride!

Dan pointed out CNC machined aluminum cable clamps are a thing, but those are sized for larger frame tubes than the 1.0 inch steel used on our Tour Easy ‘bents and, although I’ve shimmed everything else on the frame, I wanted to tweak the cable angle to match the arm on the derailleur.

A bit of OpenSCAD wrangling produces a likely candidate:

Front Derailleur Cable Clamp - Slic3r — Front Derailleur Cable Clamp – Slic3r

That’s a bulked-up revision of the prototype:

Tour Easy Front Derailleur Cable Clamp - installed — Tour Easy Front Derailleur Cable Clamp – installed

Done up in orange PETG, it demonstrated the idea worked, but two perimeter threads wrapped around 15% infill isn’t quite up to the task. Note the split along the screw on the far half and various irregularities around the ferrule.

The cable angle isn’t quite right, either, as the proper compound angle would, alas, aim the cable into the pedal crank. The bulky bushings get in the way of putting the ferrule where it should be with the screws aligned in a tidy manner, so I must get used to the jaunty angle.

The bulkier version, done with 50% infill and four perimeter threads, has the same tilt angle, but the ferrule sits further from the screws:

Tour Easy Front Derailleur Cable Clamp V2 - rear quarter view — Tour Easy Front Derailleur Cable Clamp V2 – rear quarter view

The view from the left side shows the cable angles slightly to the rear, but the smaller angle should make it happier:

Tour Easy Front Derailleur Cable Clamp V2 - side view — Tour Easy Front Derailleur Cable Clamp V2 – side view

Probably should have used black PETG. Next time, for sure!

The OpenSCAD source code as a GitHub Gist:

	// Tour Easy Derailleur Cable Clamp
	// Ed Nisley KE4ZNU – June 2017

	/* [Build Options] */

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

	/* [Extrusion] */

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

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

	/* [Hidden] */

	Protrusion = 0.01; // [0.01, 0.1]

	HoleWindage = 0.2;

	ID = 0;
	OD = 1;
	LENGTH = 2;

	/* [Cable Clamp] */

	FrameOD = 25.7; // Tour Easy has hard inch tubing + paint

	Ferrule = [1.5,5.1,12.0]; // cable ferrule

	EntryPoint = [0,13,60]; // cable entry to derailleur, +Y to rear of bike

	CableTilt = -20; // tilt from parallel to frame tube
	CableTheta = 0; // rotation around clamp from +X axis

	/* [Screws and Inserts] */

	ClampScrew = [3.0,5.5,35.0]; // M3 button / socket head cap screw
	ClampWasher = [3.7,7.0,0.7]; // M3 washer
	ClampNut = [3.0,6.0,4.0]; // M3 nylock nut

	/*
	ClampScrew = [4.0,7.0,25.0]; // M4 button head cap screw
	ClampWasher = [4.5,9.0,0.8]; // M4 washer
	ClampNut = [4.0,8.0,5.0]; // M4 nylock nut
	*/

	NutShift = -0; // slide bushing toward nut for clearance

	//- Set clamp ring dimensions

	WallThick = 10.0;

	BushingSides = 8;

	Bushing = [ClampScrew[ID],
	// ClampWasher[OD]/cos(180/8) + 4*ThreadWidth,
	Ferrule[LENGTH]/cos(180/BushingSides),
	ClampScrew[LENGTH] – 2*ClampWasher[LENGTH] – ClampNut[LENGTH]];

	Ring = [FrameOD + HoleWindage,FrameOD + 2*WallThick,Ferrule[LENGTH]];

	ClampScrewOC = IntegerMultiple(FrameOD + ClampWasher[OD],1);
	echo(str(" screw OC: ",ClampScrewOC));

	ClampKerf = 0.75; // kerf between separated halves

	NumSides = 8*4;

	//- 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);
	}


	// Construct things

	module ClampRing() {
	difference() {
	union() {
	cylinder(d=Ring[OD],h=Ring[LENGTH],$fn=NumSides); // basic ring

	for (j=[-1,1]) // screw bushings
	translate([Bushing[LENGTH]/2 + NutShift,j*ClampScrewOC/2,Ring[LENGTH]/2])
	rotate([0,-90,0]) rotate(180/BushingSides)
	cylinder(d=Bushing[OD],h=Bushing[LENGTH],$fn=BushingSides);

	intersection() {
	rotate([CableTilt,0,CableTheta]) // reinforce cable ferrule
	translate([(Ring[ID] + Ring[OD])/4,0,Ferrule[LENGTH]/2])
	rotate(180/8)
	cylinder(d=3Ferrule[OD] + 0ThreadWidth,2*Ferrule[LENGTH],center=true,$fn=8);
	cylinder(d=2*Ring[OD],h=Ring[LENGTH],$fn=NumSides); // basic ring
	}
	}

	translate([0,0,-Protrusion]) // frame tube
	cylinder(d=Ring[ID],h=Ring[LENGTH] + 2*Protrusion,$fn=NumSides);

	rotate([CableTilt,0,CableTheta]) // cable ferrule
	translate([(Ring[ID] + Ring[OD])/4,0,-0.25*Ferrule[LENGTH]]) {
	rotate(180/8)
	PolyCyl(Ferrule[OD],Ferrule[LENGTH],8);
	rotate(-22.5)
	PolyCyl(Ferrule[ID],2*Ferrule[LENGTH],4);
	}

	for (j=[-1,1]) // screw holes
	translate([Ring[OD]/2,j*ClampScrewOC/2,Ring[LENGTH]/2])
	rotate([0,-90,0]) rotate(180/6)
	PolyCyl(Bushing[ID],Ring[OD],6);

	for (i=[-1,1], j=[-1,1]) // screw & nut seats
	translate([i(Bushing[LENGTH]/2) + NutShift,jClampScrewOC/2,Ring[LENGTH]/2])
	rotate([0,i*90,0]) rotate(180/BushingSides)
	cylinder(d=Bushing[OD],h=Bushing[LENGTH],$fn=BushingSides);

	translate([0,0,Ring[LENGTH]/2]) // slice it apart
	cube([ClampKerf,2Ring[OD],2Ring[LENGTH]],center=true);
	}
	}


	//- Build things

	if (Layout == "Show") {
	translate(EntryPoint)
	cube(1,center=true);
	ClampRing();
	}

	if (Layout == "Build") {
	ClampRing();
	}

view raw Derailleur Cable Clamp.scad hosted with ❤ by GitHub

2018-06-08

Siglent SDS2304X Screen Shot File

Poking the Print button on the front of the Siglent SDS2304X scope saves the screen to a BMP file (in the /BMP directory) on a USB flash drive plugged into its front-panel port:

Which produces files like these:

ll --block-size=1 /path-to-USB-stick/BMP/
total 2318336
drwxr-xr-x 2 ed ed    4096 May 23 13:13 ./
drwxr-xr-x 4 ed ed    4096 Dec 31  1969 ../
-rw-r--r-- 1 ed ed 1152054 May 23 13:13 SDS00001.BMP
-rw-r--r-- 1 ed ed 1152054 May 23 13:13 SDS00002.BMP

The files are 1152054 bytes long, as specified by the BMP header inside the file:

hexdump -C /path-to-USB-stick/BMP/SDS00001.BMP | head
00000000  42 4d 36 94 11 00 00 00  00 00 36 00 00 00 28 00  |BM6.......6...(.|
00000010  00 00 20 03 00 00 e0 01  00 00 01 00 18 00 00 00  |.. .............|
00000020  00 00 00 94 11 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 00 00 00 00 00 01 01  01 01 01 01 01 01 01 01  |................|
00000040  01 01 01 01 01 01 01 01  01 01 01 01 01 01 01 01  |................|
*
00000880  01 01 01 01 01 01 01 01  01 01 01 01 01 01 1e 1e  |................|
00000890  1e 1e 1e 1e 1e 1e 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
*
00000990  1e 1e 1e 1e 1e 1e 01 01  01 01 01 01 01 01 01 01  |................|

The first 14 bytes contain the Bitmap file header, with the file size in Little-Endian order in the four bytes at offset +0x02: 0x00119436 = 1152054.

The four bytes at offset +0x0A give the offset of the pixel data: +0x36. That’s the series of 0x01 bytes in the fourth row. Unlike most images, BMP pixel arrays start at the lower left corner of the image and proceed rightward / upward to the last pixel at the upper right corner.

The data between the Bitmap file header and the start of the pixel data contains at least a Device Independent Bitmap header, identified by its length in the first four bytes at offset +0x0E. In this case, the length of 0x28 = 40 bytes makes it a Windows (no surprise) header.

The two bytes at +1C give the bits-per-pixel value: 0x18 = 24 = 3 bytes/pixel, so parse the pixels in RGB order.

The four bytes at +0x12 give the bitmap width in pixels: 0x320 = 800. Each pixel row must be a multiple of 4 bytes long, which works out fine at 2400 bytes.

The tail end of the file shows one dark pixel at the upper right:

hexdump -C /path-to-USB-stick/BMP/SDS00001.BMP | tail
00118330  00 cc 00 00 cc 00 00 cc  00 00 cc 00 00 cc 00 00  |................|
00118340  cc 00 00 cc 00 00 cc 00  00 cc 00 00 cc 00 00 cc  |................|
00118350  00 00 cc 00 00 cc 00 00  cc 0f 0f 75 1e 1e 1e 1e  |...........u....|
00118360  1e 1e 1e 1e 1e 1e 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
*
00118ad0  1e 1e 1e 01 01 01 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
00118ae0  1e 1e 1e 1e 1e 1e 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
*
00119430  1e 1e 1e 01 01 01                                 |......|

Which looks like this, expanded by a factor of eight (clicky for more dots to reveal the situation):

Screenshot - upper right corner - 8x expansion — Screenshot – upper right corner – 8x expansion

The scope can also transfer a screenshot over the network:

lxi screenshot -a 192.168.1.42 /tmp/lxi-shot.bmp 
Loaded siglent-sds screenshot plugin
Saved screenshot image to /tmp/lxi-shot.bmp

Which has the same header:

hexdump -C /tmp/lxi.bmp | head
00000000  42 4d 36 94 11 00 00 00  00 00 36 00 00 00 28 00  |BM6.......6...(.|
00000010  00 00 20 03 00 00 e0 01  00 00 01 00 18 00 00 00  |.. .............|
00000020  00 00 00 94 11 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 00 00 00 00 00 01 01  01 01 01 01 01 01 01 01  |................|
00000040  01 01 01 01 01 01 01 01  01 01 01 01 01 01 01 01  |................|
*
00000880  01 01 01 01 01 01 01 01  01 01 01 01 01 01 1e 1e  |................|
00000890  1e 1e 1e 1e 1e 1e 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
*
00000990  1e 1e 1e 1e 1e 1e 01 01  01 01 01 01 01 01 01 01  |................|

But the resulting file is three bytes = one pixel (!) too large:

ll --block-size=1 /tmp/lxi.bmp
-rw-rw-r-- 1 ed ed 1152057 May 23 19:09 /tmp/lxi.bmp

The tail end of the file:

hexdump -C /tmp/lxi.bmp | tail
00118330  00 cc 00 00 cc 00 00 cc  00 00 cc 00 00 cc 00 00  |................|
00118340  cc 00 00 cc 00 00 cc 00  00 cc 00 00 cc 00 00 cc  |................|
00118350  00 00 cc 00 00 cc 00 00  cc 0f 0f 75 1e 1e 1e 1e  |...........u....|
00118360  1e 1e 1e 1e 1e 1e 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
*
00118ad0  1e 1e 1e 01 01 01 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
00118ae0  1e 1e 1e 1e 1e 1e 1e 1e  1e 1e 1e 1e 1e 1e 1e 1e  |................|
*
00119430  1e 1e 1e 01 01 01 01 01  0a                       |.........|

Because the file header doesn’t include those three bytes, they don’t go into the image and the resulting screenshot is visually the same.

Which looks like a picket-fence error, doesn’t it? I’d lay long odds the erroneous loop runs from 0 to NUMPIXELS, rather than 0 to NUMPIXELS-1. Raise your hand if you’ve ever made that exact mistake.

I have no practical way to determine whether the error is inside the scope or the LXI network code, but given Siglent’s overall attention to software fit-and-finish, I suspect the former.

One can convert BMP files to the much more compact PNG format:

convert /tmp/lxi.bmp /tmp/lxi.png
convert: length and filesize do not match `/tmp/lxi.bmp' @ warning/bmp.c/ReadBMPImage/829.

Yes. Yes, there is a mismatch.

The space savings is impressive, particularly in light of PNG being a lossless format:

ll /tmp/lxi.*
-rw-rw-r-- 1 ed ed 1.1M May 23 19:09 /tmp/lxi.bmp
-rw-rw-r-- 1 ed ed  14K May 23 19:17 /tmp/lxi.png

You can eliminate the nag by truncating the file:

truncate --size=1152054 /tmp/lxi.bmp

One could wrap it all up in a script:

#!/bin/bash
lxi screenshot -a 192.168.1.42 /tmp/"$1".bmp
truncate --size=1152054 /tmp/"$1".bmp
convert /tmp/"$1".bmp "$1".png
echo Screenshot: "$1".png

And then It Just Works:

getsds2304x.sh "Test Shot Starfish"
Loaded siglent-sds screenshot plugin
Saved screenshot image to /tmp/Test Shot Starfish.bmp
Screenshot: Test Shot Starfish.png

SpaceX uses Test Shot Starfish tracks for pre-launch background music; the actual test shot was spectacular.

2018-05-30

LXI-Tools for Siglent SDS2304X Oscilloscope and SDM3045X Multimeter

For whatever reason, my Siglent SDS2304X Oscilloscope and SDM3045X Multimeter partially implement their documented command sets through partial implementations of the VXI instrumentation driver network protocol. The Linux command-line side comes from lxi-tools, which one must fetch from its repository and compile from source(do liblxi first, then lxi-tools) through the usual ./configure - make - sudo make install process, after tediously installing whatever dependencies might be revealed by incremental progress through the configuration(s) on your system(s).

The alternative, of course, is Labview on Windows.

The SDS2304X scope doesn’t respond to the LXI discover broadcast, so you must know and specify its IP address in the command. It’s easiest to configure the Siglent instruments at fixed IP addresses and be done with it:

lxi scpi -a 192.168.1.41 "*idn?"
Siglent Technologies,SDM3045X,SDM34whatever,5.01.01.03
lxi scpi -a 192.168.1.42 "*idn?"
*IDN SIGLENT,SDS2304X,SDS2Xwhatever,1.2.2.2 R10

Although the LXI tools also come in a Snap package, installing them that way prevents storing files outside the user’s home directory; having evolved a fairly extensive NFS filesystem, Snaps seem basically useless for my purposes. I don’t see much more security exposure from downloading and running a Snap than from downloading, compiling, and running the source code, but they obviously know what’s best for me.

2018-05-29

Category: Software

Rubber Soaker Hose Repair

Tour Easy Front Fender Clip: Longer and Stronger

Copying Action Camera Video: Now With UUIDs

Xubuntu 18.04 vs. VNC

Tour Easy Front Derailleur Cable Clamp

Siglent SDS2304X Screen Shot File

LXI-Tools for Siglent SDS2304X Oscilloscope and SDM3045X Multimeter