Improvements – Page 133 – The Smell of Molten Projects in the Morning

Canon LiDE 120 Scanner vs. SANE

I just replaced a cheap old Canon LiDE 30 flatbed scanner with a cheap new LiDE 120, only to get flat-black scans. The machinery worked (yes, I released the travel lock), everything seemed fine, the images were the proper size, but they were dead black.

Of course, the scanner worked OK on the Token Windows Box, but wow what crappy software they include.

Turns out the LiDE 120 requires the latest-and-greatest version 1.0.27 of the various SANE programs & libraries. Mercifully, getting those didn’t require compiling from source, just setting up the maintainer’s PPA of the most recent stable release:

sudo add-apt-repository ppa:rolfbensch/sane-release
sudo apt-get update
sudo apt-get upgrade

Which introduced circular dependencies with the distro-installed version 1.0.25 files, which I solved by ripping the entire SANE Thing out by the root(s) and reinstalling it to (re)synchronize All The Things:

sudo apt-get remove libsane:i386 sane sane-utils xsane libsane-common ia32-libs libsane
sudo apt-get install libsane:i386 sane sane-utils xsane libsane-common ia32-libs libsane

And then It Just Worked:

Of course, you must keep this WARNING in mind:

Canon LiDE 120 - Legal Issues Warning — Canon LiDE 120 – Legal Issues Warning

Franklin didn’t know about scanners or color laser printers when he observed:

Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety

Of course, there’s more to the story, but one should:

Never let the truth get in the way of a good story.

2017-07-04

LM75A vs. SOIC Adapter: Mirror Imaging

After hairballing an LM75A I²C temperature sensor to verify at least one of the eBay lot worked, a bag of SOIC-to-DIP space transformers arrived, so I soldered up another LM75A:

LM75A on DIP8 adapter - top — LM75A on DIP8 adapter – top

The SOIC chip pattern sits at right angles to the DIP pins, which took some getting used to.

The slightly defocused wire connecting pin 4 (on the IC) to pins 5, 6, and 7 (on the PCB) selects address 0x48.

So I flipped it over, soldered four wires (+5 V, GND, SDA, SCL) to the numbered pins on bottom of the board, made up a little header for the other end, wired a socket strip on the crystal tester board, plugged it in, and … nothing worked.

Turns out that the other side of the board carries a TSSOP pattern, which I’d neatly masked off with a snippet of Kapton tape, surrounded by eight numbered pins. Of course, those pin numbers correspond to the TSSOP pattern facing you, so they’re mirror-imaged for the SOIC pattern on the other side.

Soooo, the proper wiring for the SOIC pattern as seen from the TSSOP side has the pin numbers exactly bass-ackwards:

LM75A on DIP8 adapter - bottom — LM75A on DIP8 adapter – bottom

The insulation looked a lot better the first time I soldered the wires to the PCB. Honest.

Anyhow, when correctly wired, the LM75A worked as it should:

LM75A Temperature Sensor - installed — LM75A Temperature Sensor – installed

It’s snuggled chip-down against the top of the 125 MHz oscillator can, with a dab of heatsink compound improving their thermal bond and a yellow cable tie around the foam holding them together. The socket header is wired pin-for-pin to the DAC I²C socket directly above it.

The OLED temperature display shows 28.250 °C, because the oscillator just started up in a cool basement. It’ll eventually settle around 39-ish °C, where its output should be pretty close to the 125 MHz – 344 Hz value hardcoded into the source.

Oh, that’s a 3 mm amber LED next to the relay can: much less glaring than the white LED, no matter what it looks like here.

2017-06-27

Mailing Tube End Caps: Screw-in Version

The mailing tube arrived with contents intact, although the USPS inlet scanning didn’t work and the tube pretty much teleported across several states without leaving any tracking data behind. The recipient suggested several modifications to the caps:

Review of user experience of tube end:
The ribs on the endcap are very good at holding the cap on, so much so that I had to use a prying implement to remove it, which cracked the flange.
Would consider less depth on the cap, and possibly another layer on the flange.

Some continuous process improvement (a.k.a OpenSCAD hackage) produced a swoopy threaded cap with thumb-and-finger grips:

Mailing Tube Screw Cap - top - Slic3r — Mailing Tube Screw Cap – top – Slic3r

The finger grips are what’s left after stepping a sphere out of the cap while rotating it around the middle:

Mailing Tube Cap - finger grip construction — Mailing Tube Cap – finger grip construction

That worked out surprisingly well, with the deep end providing enough of a vertical-ish surface to push against.

The two hex holes fit a pin wrench, because the grips twist only one way: outward. The wrench eliminates the need for a flange, as you can now adjust the cap insertion before slathering packing tape over the ends. Man, I loves me some good late binding action!

A three-start thread seemed like overkill, but was quick & easy. The “thread form” consists of square rods sunk into the cap perimeter, with one edge sticking out:

Mailing Tube Cap - thread detail — Mailing Tube Cap – thread detail

They’re 1.05 times longer than the cap perimeter facets to make their ends overlap, although they’re not tapered like the ones in the broom handle dingus, because it didn’t (seem to) make any difference to the model’s manifoldhood.

Not needing any endcaps right now, I built one for show-n-tell:

Threaded mailing tube end cap - installed — Threaded mailing tube end cap – installed

The OpenSCAD source code as a GitHub Gist:

	// Mailing tube end cap
	// Ed Nisley KE4ZNU – June 2017

	Layout = "Build";

	Model = "Screw";

	//- Extrusion parameters – must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

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

	Protrusion = 0.1;

	HoleWindage = 0.2;

	//- Screw sizes

	inch = 25.4;

	TubeID = 2 * inch;
	TubeWall = 0.1 * inch;

	CapInsert = 15.0;
	CapRim = 6*ThreadThick;
	CapWall = 3*ThreadWidth;

	NumFlanges = 3;
	FlangeHeight = 3*ThreadThick;
	FlangeWidth = ThreadWidth/2;
	FlangeSpace = CapInsert / (NumFlanges + 1);

	ThumbHoleOD = 20.0;
	ThumbHoleAngle = 100;
	ThumbHoleSteps = 10;

	SpannerPinOD = 5.0;
	HelixOD = 4*ThreadThick;
	HelixHeight = 0.75*CapInsert;
	HelixAngle = atan(HelixHeight/(PI*TubeID));
	HelixStarts = 3;

	OAHeight = CapInsert + CapRim;

	NumRibs = 3*4;
	NumSides = 3*NumRibs;

	//- 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);
	}

	module ScrewCap() {

	union() {

	difference() {
	cylinder(d=TubeID,h=OAHeight,$fn=NumSides);

	for (a=[0,180])
	for (i=[0:ThumbHoleSteps-1])
	rotate(a + i*ThumbHoleAngle/ThumbHoleSteps)
	translate([TubeID/4,0,-iThumbHoleOD/(2ThumbHoleSteps)])
	sphere(d=ThumbHoleOD);

	for (a=[0,180])
	rotate(a – 60)
	translate([0.75*TubeID/2,0,-Protrusion])
	rotate(0*180/6)
	PolyCyl(SpannerPinOD,0.75*CapInsert,6);
	}

	for (s=[0:HelixStarts-1])
	for (i=[0:NumSides-1])
	rotate(i360/NumSides + 180/NumSides + s360/HelixStarts)
	translate([TubeID/2 – 0.25HelixOD,0,iHelixHeight/NumSides + HelixOD])
	rotate([90 + HelixAngle,0,0])
	cylinder(d=HelixOD,h=1.05PITubeID/NumSides,center=true,$fn=4);
	}

	}

	module PushCap() {

	difference() {
	cylinder(d=TubeID,h=OAHeight,$fn=NumSides);
	translate([0,0,CapWall])
	cylinder(d=TubeID – 2*CapWall,h=OAHeight,$fn=NumSides);
	}

	for (i=[1:NumFlanges])
	translate([0,0,i*FlangeSpace])
	difference() {
	cylinder(d=TubeID + 2*FlangeWidth,h=FlangeHeight,$fn=NumSides);
	translate([0,0,-Protrusion])
	cylinder(d=TubeID – 2CapWall,h=FlangeHeight + 2Protrusion,$fn=NumSides);
	}

	for (i=[0:NumRibs-1])
	rotate(i*360/NumRibs)
	translate([0,-ThreadWidth,CapWall + ThreadThick])
	cube([TubeID/2 – CapWall/2,2*ThreadWidth,CapInsert + CapRim – CapWall – ThreadThick],center=false);

	translate([0,0,CapInsert]) {
	difference() {
	cylinder(d=TubeID + 2*TubeWall,h=CapRim,$fn=NumSides);
	translate([0,0,-Protrusion])
	cylinder(d=TubeID – 32CapWall,h=2*CapRim,$fn=NumSides);
	}
	}
	}

	//- Build things

	if (Model == "Push")
	if (Layout == "Show")
	PushCap();
	else if (Layout == "Build")
	translate([0,0,OAHeight])
	rotate([180,0,0])
	PushCap();

	if (Model == "Screw")
	if (Layout == "Show")
	ScrewCap();
	else if (Layout == "Build")
	translate([0,0,OAHeight])
	rotate([180,0,0])
	ScrewCap();

view raw Mailing Tube Cap.scad hosted with ❤ by GitHub

2017-06-26

Handbag Strap Rivet Repair

One of the leather strap anchors on Mary’s giant haul-everything-to-a-concert(*) handbag pulled its rivet through the canvas fabric:

Handbag - pulled-through rivet — Handbag – pulled-through rivet

We knotted the strap around the zippered opening and completed the mission.

Of course, it wouldn’t have pulled through if they’d splurged on washers, but noooo too expensive:

Handbag - intact rivet - inside — Handbag – intact rivet – inside

Some rummaging produced a pan-head M3 screw of suitable length:

Handbag - repaired - outside — Handbag – repaired – outside

A slightly battered acorn nut was a special treat for the inside, with another washer to keep me happy:

Handbag - repaired - inside — Handbag – repaired – inside

That was easy!

(*) At Tanglewood, where they don’t strip-search you on the way in, tow-behind coolers seemed de rigueur, and a good time was had by all.

2017-06-25

LF Crystal Tester: Bring the Noise!

The OLED display refresh contributes 100 Hz noise pulses to the low-level sine wave from the crystal test fixture:

OLED Enabled - 100 Hz display refresh — OLED Enabled – 100 Hz display refresh

Disabling the display by activating its powersave option reveals 60 Hz pulses from the USB port on the Arduino Nano:

OLED Powersave - 60 Hz USB Ground Loop — OLED Powersave – 60 Hz USB Ground Loop

Unplugging the USB cable, leaving just the +5 VDC power supply and coax cable to the oscilloscope, solves most of the problem:

OLED Powersave - USB unplugged — OLED Powersave – USB unplugged

A closer look shows some (relatively) low frequency noise remains in full effect:

OLED Powersave - USB unplugged - detail — OLED Powersave – USB unplugged – detail

Disabling the display while measuring the crystal seems sensible, although, to avoid surprises, a pushbutton should start the process. Unplugging the USB port puts a real crimp in the data collection, although that’s probably survivable with a USB isolator, one of which is on the way around the planet.

The remaining low-level chop requires more thought. Somewhat to my surprise, holding the Arduino Reset button down doesn’t change much of anything, so it’s not a firmware thing.

Those 10 µF coupling caps gotta go.

With the OLED dark and the USB carrying data:

Spectrum - OLED Powersave - USB in — Spectrum – OLED Powersave – USB in

Compare that to the first pass:

Tamping down the noise seems to reduce the overall amplitude variation, but it also makes the capacitor-in and capacitor-out curves more consistent. There may be other things going on that I haven’t accounted for.

The peak frequencies differ by 0.2 Hz, which is probably due to a few degrees of temperature difference. Obviously, it’s badly in need of a temperature calibration & correction.

2017-06-23

LF Crystal Tester: Pretty Plots

A slight modification spits out the (actual) frequency and dBV response (without subtracting the 108 dB intercept to avoid negative numbers for now) to the serial port in CSV format, wherein a quick copypasta into a LibreOffice Calc spreadsheet produces this:

Changing the center frequency and swapping in a 60 kHz resonator:

Much prettier than the raw scope shot with the same data, there can be no denyin’:

Log V vs F - 32766 4 Hz - CX overlay — Log V vs F – 32766 4 Hz – CX overlay

I think the wobbulations around the parallel resonant dip come from the excessively hugely too large 10 µF caps in the signal path, particularly right before the log amp input, although the video bandwidth hack on the AD8310 module may contribute to the problem. In any event, I can see the log amp output wobbling for about a second, which is way too long.

Anyhow, the series-resonant peaks look about 1 Hz wide at the -3 dBV points, more or less agreeing with what I found with the HP 8591 spectrum analyzer. The series cap is a bit smaller, producing a slightly larger frequency change in the series resonant frequency: a bit under 2 Hz, rather than the 1 Hz estimated with the function generator and spectrum analyzer.

I still don’t understand why the parallel resonant dip changes, although I haven’t actually done the pencil pushing required for true understanding.

Ain’t they lovely, though?

2017-06-19

Proto Board Holder: Revised Screw Mounts

Improving the crystal tester’s (nonexistent) grounding requires a band of copper tape around the inside of the proto board holder. Rather than cut the tape lengthwise to fit the holder, a new one will be just tall enough:

Proto Board - 80x120 - revised inserts - Slic3r — Proto Board – 80×120 – revised inserts – Slic3r

While I was at it, I deleted the washer recesses, because those didn’t work out well, and fiddled the screw holes to put the inserts in from the bottom:

Proto Board - 80x120 - revised inserts - detail - Slic3r — Proto Board – 80×120 – revised inserts – detail – Slic3r

Although the overhang inside the holes will be ugly, I’ll epoxy the inserts flush with the bottom and nobody will ever know.

The copper tape now makes a tidy ground strap:

Crystal Tester - ground strap - rear — Crystal Tester – ground strap – rear

With a gap in the front to eliminate the obvious loop:

Crystal Tester - ground strap - front gap — Crystal Tester – ground strap – front gap

The OpenSCAD source code as a GitHub Gist:

	// Test support frame for proto boards
	// Ed Nisley KE4ZNU – Jan 2017
	// June 2017 – Add side-mount bracket, inserts into bottom

	Layout = "Frame";

	ClampFlange = true;

	Channel = false;

	//- Extrusion parameters – must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

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

	Protrusion = 0.1;

	HoleWindage = 0.2;

	//- Screw sizes

	inch = 25.4;

	Tap4_40 = 0.089 * inch;
	Clear4_40 = 0.110 * inch;
	Head4_40 = 0.211 * inch;
	Head4_40Thick = 0.065 * inch;
	Nut4_40Dia = 0.228 * inch;
	Nut4_40Thick = 0.086 * inch;
	Washer4_40OD = 0.270 * inch;
	Washer4_40ID = 0.123 * inch;

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

	Insert = [3.9,4.6,5.8];

	//- PCB sizes

	PCBSize = [80.0,120.0,1.6];
	PCBShelf = 1.0; // support rim under PCB

	Clearance = 2*[ThreadWidth,ThreadWidth,0];

	WallThick = 4.0;
	FrameHeight = IntegerMultiple(3/8 * inch,1.0);
	echo(str("Inner height: ",FrameHeight));

	ScrewOffset = 0.0 + Clear4_40/2;

	ScrewSites = [[-1,1],[-1,1]]; // -1/0/+1 = left/mid/right and bottom/mid/top

	OAHeight = FrameHeight + Clearance[2] + PCBSize[2];
	echo(str("OAH: ",OAHeight));

	FlangeExtension = 3.0;
	FlangeThick = IntegerMultiple(2.0,ThreadThick);
	Flange = PCBSize
	+ 2*[ScrewOffset,ScrewOffset,0]
	+ 2*[Washer4_40OD,Washer4_40OD,0]
	+ [2FlangeExtension,2FlangeExtension,(FlangeThick – PCBSize[2])]
	;

	echo(str("Flange: ",Flange));
	NumSides = 4*5;

	WireChannel = [Flange[0],15.0,3.0 + PCBSize[2]];
	WireChannelOffset = [Flange[0]/2,25.0,(FrameHeight + PCBSize[2] – WireChannel[2]/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);
	}

	//- Build things

	if (Layout == "Frame")
	difference() {
	union() { // body block
	translate([0,0,OAHeight/2])
	cube(PCBSize + Clearance + [2WallThick,2WallThick,FrameHeight],center=true);

	for (x=[-1,1], y=[-1,1]) { // screw bosses
	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	0])
	cylinder(r=Washer4_40OD,h=OAHeight,$fn=NumSides);
	}

	if (ClampFlange) // flange for work holder
	linear_extrude(height=Flange[2])
	hull()
	for (i=[-1,1], j=[-1,1]) {
	translate([i(Flange[0]/2 – Washer4_40OD/2),j(Flange[1]/2 – Washer4_40OD/2)])
	circle(d=Washer4_40OD,$fn=NumSides);
	}
	}

	for (x=[-1,1], y=[-1,1]) { // screw position indexes

	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	-Protrusion])
	rotate(xy180/(2*6))
	PolyCyl(Clear4_40,(OAHeight + 2*Protrusion),6); // screw clearance holes

	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	-Protrusion])
	rotate(xy180/(2*6))
	PolyCyl(Insert[OD],OAHeight – PCBSize[2] – 3*ThreadThick + Protrusion,6); // inserts

	if (false)
	translate([x*(PCBSize[0]/2 + ScrewOffset),
	y*(PCBSize[1]/2 + ScrewOffset),
	OAHeight – PCBSize[2]])
	PolyCyl(1.2*Washer4_40OD,(PCBSize[2] + Protrusion),NumSides); // washer recess
	}

	translate([0,0,OAHeight/2]) // through hole below PCB
	cube(PCBSize – 2[PCBShelf,PCBShelf,0] + [0,0,2OAHeight],center=true);

	translate([0,0,(OAHeight – (PCBSize[2] + Clearance[2])/2 + Protrusion/2)]) // PCB pocket on top
	cube(PCBSize + Clearance + [0,0,Protrusion],center=true);

	if (Channel)
	translate(WireChannelOffset) // opening for wires from bottom side
	cube(WireChannel + [0,0,Protrusion],center=true);
	}

	// Add-on bracket to hold smaller PCB upright at edge

	PCB2Insert = [3.0,4.9,4.1];
	PCB2OC = 45.0;

	if (Layout == "Bracket")
	difference() {
	hull() // frame body block
	for (x=[-1,1]) // bosses around screws
	translate([x*(PCBSize[0]/2 + ScrewOffset),0,0])
	cylinder(r=Washer4_40OD,h=OAHeight,$fn=NumSides);

	for (x=[-1,1]) // frame screw holes
	translate([x*(PCBSize[0]/2 + ScrewOffset),0,-Protrusion])
	rotate(x180/(26))
	PolyCyl(Clear4_40,(OAHeight + 2*Protrusion),6);

	for (x=[-1,1]) // PCB insert holes
	translate([x*PCB2OC/2,(Washer4_40OD + Protrusion),OAHeight/2])
	rotate([90,0,0])
	cylinder(d=PCB2Insert[OD],h=2*(Washer4_40OD + Protrusion),$fn=6);

	}

view raw Proto Board Holder.scad hosted with ❤ by GitHub

2017-06-13