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Archive for October, 2019

3D Foot Scanning

The Poughkeepsie Library makes a 3DSystems Sense scanner (V1) available to patrons and, after a bit of to-and-fro, I managed to get a not-awful scan of Mary’s right leg:

Mary - R foot - complete
Mary – R foot – complete

This was accomplished under field conditions in a cramped room hosting a Spanish-language “introduction to computers” class. We propped her leg across the edge of a table with her sock as a cushion.

The depth image resolution seems to be 1 mm and the software attempts to stitch multiple views from different angles into a consistent 3D model. The scanner requires a steady hand and a steady model to successfully glue new data onto the existing model; what seem small misalignments derail the matching.

The software has several presets, of which “Head” produces the best results. I have no idea what the algorithm thinks of her foot; maybe it’s been trained on some truly ugly faces.

Exporting the solid model as either STL or PLY allows import into (Windows-only) Meshmixer, wherein I sawed off the pieces we won’t need:

Mary R foot trimmed
Mary R foot trimmed

If only I had a foot fetish …

The 3DSystems software requires a fairly specific Windows 8 (or 10, which is so not happening) + Intel hardware configuration, which recently arrived as a $250 off-lease Dell Latitude 7250 laptop. It works fine through VNC, so I can use it from the Comfy Desk.

However, using a 3D scanner in your own home isn’t actually private:

3DSystems Sense Scanner - EULA
3DSystems Sense Scanner – EULA

All your data are belong to them:

3D Systems may also automatically collect and report back to 3D Systems information about the Software and Licensee’s usage along with limited information about the Device, 3D Printer, and/or other third-party applications. If 3D Systems implements automated data collection practices then Licensee may opt out of providing such data if Licensee has a license that authorizes Commercial Use.

Oh, and then you must activate the software before using it. The library IT folks tell me I can install & activate the scanner on my system without derailing their setup. I have my doubts, but we’ll see how it goes.

I must get into photogrammetry, ideally from the sofware libre branch as described there. The openMVG repo seems promising.

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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
Spider vs. Marmorated Stink Bug

Looks like a week’s worth of spider chow!

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Pride Lift Chair Control Dimming

For reasons not relevant here, we recently decontaminated a second lift chair, this one in bariatric size (so it doesn’t suffer from fuzz-shaving struts) with a six-switch control pod:

Pride lift chair control - dimmed LEDs
Pride lift chair control – dimmed LEDs

The green LED-lit buttons were so bright I took it apart to see what could be done; the picture shows the considerably dimmed result.

Start by prying outward on the tab at the USB charging port:

Pride lift chair control - USB port latch
Pride lift chair control – USB port latch

Done right, you can then release the latches along the sides:

Pride lift chair control - side opened
Pride lift chair control – side opened

It’s impossible to photograph the PCB with the LEDs active, but here’s what it looks like without power:

Pride lift chair control - PCB overview
Pride lift chair control – PCB overview

The eight (!) SMD LEDs align with light pipes around the switch openings:

Pride lift chair control - button keys
Pride lift chair control – button keys

The black dots come from Sharpie ink daubed in the shallow recesses intended to nestle around the LEDs. Note that the four switch caps have unique keying, so you can’t put them back incorrectly without some effort.

While we’re inside, here’s a closer look at the cable entry point, just in case I must replace the industrial-strength coily cord:

Pride lift chair control - cable entry
Pride lift chair control – cable entry

Unfortunately, it has a five-conductor cable, so a cheap phone coily cord (remember when phones had coily cords?) won’t suffice.

The PCB sports a pair of PICs, one of which seems to handle the buttons. I betcha the cable dates back to the days of hard-wired power switches, with the PIC now handling the intricate logic of deciding which motors to actuate for each function, then controlling MOSFETs as fake switch contacts.

The other PIC snuggles against the USB interface, which the manual describes as a charging-only port. It might also serve as a programming interface for the main PIC; admittedly the notion of a firmware upgrade for a lift chair seems far-fetched.

Reassembly is in reverse order with a resounding snap at the conclusion. It works fine and you (well, I) can now look at the control pod without sunglasses.

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Hiatus

Several home projects of steadily increasing priority will interfere with writing up Basement Laboratory projects through early November:

Mary - R foot - complete
Mary – R foot – complete

Ground truths:

  • No barnacles on her foot
  • No sea creature eating her leg

I’ll be posting infrequently during the next few weeks.

All remains right with our world …

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Raspberry Pi vs. eBay Camera: Assembly Completion

I picked up a pair of Raspberry Pi V1 cameras, both of which arrived unstuck to their breakout board:

RPi V1 camera adhesive
RPi V1 camera adhesive

Requiring the customer to peel off the white layer and stick the camera to the PCB helps keep costs low. They’re $4 if you’re willing to wait two months or $7 from a “USA Seller”.

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Bathroom Sink Drain: Epoxy FAIL

Apparently, “porcelain chip fix” epoxy survives about a year in a bathroom sink:

Bathroom sink epoxy - top
Bathroom sink epoxy – top

It came loose from the drain rim while I was cleaning the sink; I wasn’t doing anything particularly vigorous.

The stain in the lower right goes all the way around the epoxy:

Bathroom sink epoxy - bottom
Bathroom sink epoxy – bottom

For what should be obvious reasons, I was loathe to scuff up the sink surface to give the epoxy a better grip, so it couldn’t make a watertight seal all the way around.

A closer look at the stain:

Bathroom sink epoxy - detail
Bathroom sink epoxy – detail

I’m reasonably sure that’s iron bacteria colony, rather than actual rust, as there’s no iron to be found anywhere nearby.

For lack of anything smarter, I’ll apply another dose of the same epoxy, although this time I won’t be expecting a long-term fix.

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CNC 3018-Pro: HD and CD Fixtures

I actually had this in mind when I laid out the hard drive and CD engraving fixtures:

CNC 3018-Pro - HD and CD fixtures
CNC 3018-Pro – HD and CD fixtures

The fixtures are centered at X±70.0 mm / Y=0.0 from the G54 workspace coordinate origin dead-center in the middle of the platform, with G55 centered on the HD fixture to the left and G56 on the CD fixture to the right.

So the engraving workflow amounts to homing the CNC 3018 when I turn it on, taping a platter in a fixture, selecting the corresponding WCS, loading a suitable G-Code file, and firing it off. It seems bCNC returns to G54 after completing the file, so verifying the WCS selection every time is Very Good Practice.

The friable lacquer coating on some CDs fills my world with glitter whenever I engrave a pattern on their label side. I didn’t plan on a dust shoe for this thing!

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