Google Pixel 3a Microscope Adapter

Hand-holding my Google Pixel 3a phone over the microscope eyepiece worked well enough to justify building Yet Another Camera Adapter:

Pixel 3a Microscope Adapter - in action
Pixel 3a Microscope Adapter – in action

The solid model looks about like you’d expect:

Google Pixel 3a Zoom Microscope Mount - solid model - top
Google Pixel 3a Zoom Microscope Mount – solid model – top

The “camera” actually has the outside dimensions of a Spigen case, rather than the bare phone, because dropping a bare phone is never a good idea.

The base plate pretty much fills the M2’s platform:

Pixel 3a Microscope Adapter - M2 platform
Pixel 3a Microscope Adapter – M2 platform

I originally arranged the four corners around the plate to print everything in one go, but an estimated six hours of print time suggested doing the corners separately would maximize local happiness. Which it did, whew, even if the plate ran for a bit over 4-1/2 hours.

The snout is a loose fit around the 5× widefield microscope eyepiece, with the difference made up in a wrap of black tape; it’s much easier to adjust the fit upward than to bore out the snout. An overwrap of tape secures the snout to the eyepiece, which I’ve dedicated to the cause; the scope normally rocks 10× widefield glass.

The tapered hole exposes the phone’s fingerprint reader to simplify unlocking, should it shut down while I’m fiddling with something else.

The microscope doesn’t fully illuminate the camera’s entrance pupil at minimum zoom, with 4.5× filling the screen and (mostly) eliminating the vignette. The corner blocks have oversize holes to allow aligning the camera lens axis over the microscope optical axis. The solid model incorporates Lessons Learned from the version you see here, because you (well, I) can’t measure the camera axis with respect to the outside dimensions accurately enough:

Pixel 3a Microscope Adapter - installed - front
Pixel 3a Microscope Adapter – installed – front

Although it’s less unsteady than it looks, microscopy requires a gentle touch at the best of times. The adapter doesn’t add much wobble to the outcome:

Pixel 3a Microscope Adapter - installed - side
Pixel 3a Microscope Adapter – installed – side

The field is about 14×19 mm with the camera at 4.5× and the microscope at minimum zoom:

Pixel 3a Microscope Adapter - test image - min mag
Pixel 3a Microscope Adapter – test image – min mag

You can see a little darkening on the upper and lower right corners, so the phone’s still minutely leftward.

The field is about 1.5×2 mm at full throttle:

Pixel 3a Microscope Adapter - test image - max mag
Pixel 3a Microscope Adapter – test image – max mag

Color balance with the cold white LED ring isn’t the best, but it’s survivable. Mad props to OpenCamera for exposing All. The. Controls. you might possibly need.

The OpenSCAD source code as a GitHub Gist:

Homage Tektronix Circuit Computer: Pen Plotter Version

A reproduction circular slide rule from the mid-1960s may not be the cutting edge of consumer demand, but the pen version of a Tektronix Circuit Computer came out pretty well:

Homage Tektronix Circuit Computer - green on white laminated
Homage Tektronix Circuit Computer – green on white laminated

A Bash script compiles the GCMC code with eight different parameter combinations to produce pairs of G-Code files to draw (“engrave” being aspirational) and cut (“mill”, likewise) the three decks and the cursor.

The CNC 3018XL with a Pilot V5RT pen draws the deck scales on white paper:

Pilot V5RT holder - installed
Pilot V5RT holder – installed

Better paper definitely produces better results, so I must rummage through the Big Box o’ Paper to see what lies within. Laminating the decks improves their durability and matches the original Tek surface finish.

The MPCNC with a drag knife blade cuts through a laminated deck like butter:

Tek CC - MPCNC drag knife
Tek CC – MPCNC drag knife

Setting the XY origin to dead center on each deck requires carefully calibrating the USB video camera, with the end result accurate to maybe ±0.1 mm around the entire perimeter. Both machines move equal linear distances along both axes, which was definitely comforting.

Having made half a dozen cursors from various bits of acrylic, none of which look particularly good, demonstrates my engraving hand is too weak for a complete slide rule:

Tek Circuit Computer - cursor hairline
Tek Circuit Computer – cursor hairline

With logarithmic scales in hand, however, adapting the GCMC source code to produce general-purpose circular slide rules with only two decks and smaller diameters may be the way to improve my engraving-fu, as a full-scale Tektronix Circuit Computer would chew up three square-foot plastic sheets.

A general-purpose slide rule would need multi-color (well, at least bi-color) labels and digits for red “inverse” scales to remind you (well, me) they read backwards. Some slipsticks use left-slanting italics, left-pointing markers (“<2”), or other weirdness, but they’re all different.

An early small-scale version engraved on ABS came out OK, modulo poor ink fill:

Tek CC bottom - ABS 160g 2400mm-min
Tek CC bottom – ABS 160g 2400mm-min

Engraving the decks on hard drive platters doesn’t count:

Tek CC - bottom deck - scaled to HD platter
Tek CC – bottom deck – scaled to HD platter

All in all, it’s been an interesting exercise and, as you may have guessed, will become a Digital Machinist column.

The GCMC and Bash source code as a GitHub Gist:

Tour Easy: Fairing Strut Mounts, Redux

Our Young Engineer’s Tour Easy followed us home, due to a non-survivable cycling commute and inadequate apartment storage space. What with its Zzipper fairing being off and having easy access to the strut, I conjured & installed another set of fairing mounting blocks:

Tour Easy - Fairing Strut Mount Blocks
Tour Easy – Fairing Strut Mount Blocks

Should you be in need of a Tour Easy recumbent in good shape, well, have I got a deal for you. I’ll even conjure a Daytime Running Light mount, if that’s what it takes …

Praying Mantis Ootheca

Several of this year’s praying mantises set up shop in the decorative grasses bracketing the front door:

Praying Mantis - brown wing covers - in grass
Praying Mantis – brown wing covers – in grass

We found their egg masses, formally called ootheca, attached to the stems in mid-October:

Praying Mantis egg mass A
Praying Mantis egg mass A

They feel like rigid urethane foam and seem eminently protective:

Praying Mantis egg mass B
Praying Mantis egg mass B

We’ll cut around the masses when it’s time to clear out the dead grass next spring. I was tempted to bring one inside, but dealing with a gazillion tiny mantises in a few months would be daunting.

Homage Tektronix Circuit Computer: Ball-point Pens vs. Paper

Extra Fine Pilot V5 pens have a 0.5 mm ball, in contrast to the 1.0 mm ball in the cheap pens I’ve been using, so they should produce much finer lines.

Which turns out to be the case:

Tek Circuit Computer - pen and paper comparison
Tek Circuit Computer – pen and paper comparison

That’s a stack of three “Homage” Tek CC bottom decks under a Genuine Tektronix Circuit Computer.

The black scale at the top of the picture (and the bottom of the stack) came from a 1 mm cheap pen in the collet holder, the two green scales come from a 0.5 mm Pilot V5RT cartridge in its new holder, and the Original is (most likely) laser-printed back when that was a New Thing.

As always, paper makes a big difference in the results. The brownish paper is 110 pound card stock with a relatively coarse surface finish. The white paper is ordinary 22 pound general-purpose laser / inkjet printer paper.

The 1.0 mm pen (top) doesn’t much care what it’s writing on, producing results on the low side of OK: some light sections, no blobs. Perfectly serviceable, but not pretty.

1.0 mm ball pen
1.0 mm ball pen

The Pilot V5RT really likes better paper, as it bleeds out on the card stock whenever the CNC 3018XL so much as pauses at the end of a stroke. Using white paper slows, but doesn’t completely stop, the bleeding, making the blobs survivable.

0.5 mm ball Pilot V5RT pen
0.5 mm ball Pilot V5RT pen

I’ve been using card stock to get stiffer, more durable, and more easily manipulated decks, but the improved line quality on the white paper says I should laminate the decks in plastic, just like the original Tektronix design.

No surprise there!

Google Pixel 3a Photomicrography vs. Ballpoint Pens

The Google Pixel 3a camera, unlike the camera in my older Google Pixel XL, takes spectacularly good images through a widefield 5X eyepiece on the stereo zoom microscope:

0.5 1.0 mm ball pens - 0.7 mm lead pencil
0.5 1.0 mm ball pens – 0.7 mm lead pencil

That’s hand-holding the phone against the eyepiece while manipulating it with the other hand. Definitely not the most stable arrangement, but the camera copes well with slight motions. I really need a gripping hand for the camera, to free up another for the microscope’s focus knob.

For the record:

Zooming in (because it’s a stereo zoom microscope and I can), the 1.0 mm ball seems surprisingly un-wetted by its ink:

1.0 mm ball pen
1.0 mm ball pen

The Pilot V5 ball seems more smoothly covered:

0.5 mm ball Pilot V5RT pen
0.5 mm ball Pilot V5RT pen

Those are at the same magnification & crop size, so they’re to the same scale.

This definitely calls for a customized phone-to-eyepiece holder!

CNC 3018XL: Pilot V5RT Pen Holder

It turns out my all-time favorite Pilot Precise V5 Extra Fine stick pen also comes in a clicky-top retractable version:

Pilot V5 and V5RT pens
Pilot V5 and V5RT pens

The cartridge is a nice 6 mm cylinder, eminently transformable into a plotter pen:

Pilot V5RT holder - installed
Pilot V5RT holder – installed

A few minutes with a caliper provides key measurements for a snout surrounding the business end:

Pilot V5RT Pen Holder - snout dimension doodle
Pilot V5RT Pen Holder – snout dimension doodle

The green letters & numbers give the nearest drill sizes. The “T” values along the bottom are the tailstock turns (at 1.5 mm/turn) required to poke the drills to the indicated depths, eyeballed when the body just enters the hole.

Having recently decomissioned the Thing-O-Matic and harvested its organs parts, I have a vast collection of 3/8 inch = 9.52 mm shafts and matching bronze bushings:

9.52 mm shaft and bushings
9.52 mm shaft and bushings

Bronze bushings have low stiction, at least when they’re co-axial, and are much shorter than linear ball bearings.

I chopped off a 70 mm length of shaft and faced the raw end:

Pilot V5RT holder - facing shaft
Pilot V5RT holder – facing shaft

The other end had a maker’s logo, but I don’t recognize it:

Pilot V5RT holder - center drill
Pilot V5RT holder – center drill

I really wanted an 8 mm bore around the snout, but it just didn’t work out. The ring around the 7.5 mm counterbore shows where the larger drill just … stopped:

Pilot V5RT holder - drilled shaft
Pilot V5RT holder – drilled shaft

A trial fit with the pen cartridge:

Pilot V5RT holder - pen in shaft
Pilot V5RT holder – pen in shaft

The top of the shaft gets a somewhat longer knurled ring for the 3 mm SHCS holding the cartridge in place:

Pilot V5RT holder - knurling pen clamp
Pilot V5RT holder – knurling pen clamp

The screw bears on a split collar turned and drilled from a Delrin rod:

Pilot V5RT holder - drilling Delrin clamp
Pilot V5RT holder – drilling Delrin clamp

The “split” came from a simple saw cut across one side and I milled a flat spot in the knurling to seat the screw. As usual, the knurled ring got epoxied to the shaft.

The snout started as a 3/8 inch aluminum rod, drilled as shown in the sketch, with a (scant) 7.5 mm section to fit the shaft. The carbide insert left a nicely rounded shoulder that required trimming to fit snugly into the shaft:

Pilot V5RT holder - shaping snout seat
Pilot V5RT holder – shaping snout seat

The compound can handle the shallow angle required to shape the snout:

Pilot V5RT holder - tapering snout
Pilot V5RT holder – tapering snout

A trial fit showed the snout was a bit too long for comfort:

Pilot V5RT holder - snout test fit
Pilot V5RT holder – snout test fit

Making something shorter doesn’t pose much of a challenge:

Pilot V5RT holder - trimming snout
Pilot V5RT holder – trimming snout

Another trial fit shows it’s spot on:

Pilot V5RT holder - shaft snout pen test fit
Pilot V5RT holder – shaft snout pen test fit

The critical part is having the snout support the plastic around the pen tip to prevent wobbulation.

Epoxy the whole thing together, add a suitable spring, tighten the screws & nuts for the reaction plate, and it’s all good. I write with about 50 g of force for these pens, so a light preload seemed in order:

Pilot V5RT Pen Holder - initial downforce measurement
Pilot V5RT Pen Holder – initial downforce measurement

If I’d weighed the full-up shaft + snout + collar + cartridge, I’d know if the Y intercept matches that weight. It seems a little lighter, but I’m not taking the thing apart to find out.

The first version of the 3D printed holder (shown above) is a straightforward modification of the LM12UU diamond drag bit holder, but, after building enough of these things, I realized the circular reaction plate should be triangular to get more clearance in front of the Z-axis stepper motor when installing & removing the holder:

Pilot V5RT Pen Holder - solid model - show view
Pilot V5RT Pen Holder – solid model – show view

It also has a recess for the serrated top of the bearing, to prevent the knurled collar from clicking annoyingly as the Z-axis rises at the end of each stroke.

Now, to see how well it draws!

The OpenSCAD source code as a GitHub Gist: