Category Archives: Objects

Selectric Cozy

Bias-tape bound seams out looks better, even if the sewing job is obviously uneven.

Some months ago I decided I wanted to play with an IBM Selectric typewriter, and after some fuckery, obtained and started working on an example of the dual-pitch, correcting Selectric II I find most appealing. At some point there will be an extended post about that, but 1. I’m not entirely sure I know what I’m talking about yet, and 2. Too much writing at the time I was working on it. This post is not about the machine, just the cover I made for it.

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An Experiment in Water Cooled 3D Printing Extrusion

Scrapheap Challenge: The world’s worst syringe pump.

Or, three hours enjoyably lost to a visit from the bad idea fairy.

My PhD advisor and I were chatting in the lab today and had an idea that it would be interesting to try to drip/jet a bit of water onto just-extruded filament, ideally in small enough quantity that it phase changed and flashed off with all the excess energy, in order to allow printing unreasonable unsupported structures.

It unfortunately doesn’t look like it will be practical, but we got a PoC-grade implementation in a few hours and it seemed worth a quick write-up to document our experiment for the interwebz.

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Bladekey Refresh

I’ve been carrying a series of slightly-customized 3D printed bolt-type bladekeys since 2014. Despite being printed PLA, I’ve only had to print a new one once every several years – I wasn’t keeping good records but I think this is my third plastic body, second #8-32 “Chicago Binding Post,” and I upgraded the type of pocket clip at some point. I’m yet to have a catastrophic failure. The setup essentially eliminates key jingle, poking, or wear on pocket facings, while still being easy to tap check and use. The only slight downside to this setup is that when I attach a car key and put it in the vehicle, the blade-key dangles at knee height and occasionally grabs a leg hair – if I drove more I’d probably tweak how I attach the car key to fix that.

Pictures from the first one I carried in 2014, and the most recent swap out, induced by it “getting loose” and letting the stack of keys flip forward in my pocket – which turned out to be the result of several cracks in the plastic body. Plus, flexing that the bitting and labels are both obscured when closed, which I suppose is a minor security feature, especially when posting pictures on the Internet.

At this point I’d buy one of the fancy ones just to support the designer, but my desired size falls in between the models they do commercially (I use 15mm W x 58 L, closest sizes are 12mm W and 19mm W). Maybe sometime I’ll get ambitious and cut one in a different material on the router.

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Aneng AN8009 DMM with Hacks

Aneng AN8009 DMM

I just picked up an Aneng AN8009 DMM as an upgrade to the cheap, cheap (but surprisingly OK) Circuit Specialists branded MY-68 I’ve had as my home on-desk approxometer for ages. It’s a nice meter for $30ish, and can be readily hacked to improve its performance. I tend to point people to mid-range Uni-T DMMs when they asked for decent hobby meters, but now I might switch to one of these plus one of those little $10 Atmega328 based component testers cloned everywhere for ~$10 as basic electronics lab instruments.

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A Bit of 3D Printer Maintenance

We were doing a bit of beginning-of-summer lab maintenance and one of the projects was to figure out why the MakerGear M2 (Which has been heavily modified over the years, Azteeg x5 mini motherboard, E3D hotend, etc.) was behaving so strangely.
Well… there’s your problem.
Fresh 0.35mm nozzle next to the bored out, abraded down corpse of a nozzle that we’ve, in retrospect, been running for something like 3 years. Turns out printers work much better when the nozzle aperture is roughly the size it’s supposed to be.
Still seeing some odd temperature fluctuation, but … look at that thing.

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E7250


I picked up a refurbished Dell Latitude E7250 (Dell’s “Premium” 12.5″ laptop, just over a generation out of date) because the little loaner Inspiron 11-3000 I’d been using as my carryin’ around laptop had become unacceptably shitty at essentially all the things I wanted to use it for. The E7250 is Superb, with notes:
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Ruideng Adjustable Bench Power Supply

I built myself a little adjustable bench power supply from Chinese modules, partly because I thought it would be handy to have one, and mostly because I wanted a small, straightforward project to do for my own sanity.

I set up a slightly different configuration than is typical, and am documenting it for funsies and/or to ease clones if anyone is so inclined. The whole project was about $60 all-in, for an (approximately) 0-34V, 0-5A adjustable bench power supply.
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MicroChorder

I hacked together an Arduino Micro firmware that is a drop-in replacement for a Spiffchorder, long version and code below the fold.
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New Backup Scheme

I’m finally not living so dangerously with the data outside my Seafile-synced live set and doing proper backups of all my machines, including laptops. I’m also now storing my various media files on a RAID instead of a single large USB hard drive dangling from whatever machine is attached to my TV. Now that the semester is over and I’ve had time to put some finishing touches on the system, here are some process docs under the fold for the use of my future-self and others – the first part is about my new home server, the second part covers the (likely more transferable) set of borg and rclone incantations, scripts, unit files, etc. that make it all work.
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Ebay DB25 Arduino Nano grbl Adapters

A second consecutive CNC post, because I haven’t had time to write up long-form posts for months, and something requiring documentation came up today.

While I’m still quite happy with LinuxCNC (especially since I discovered NativeCAM), my adviser bought himself a GRBL-DB25 adapter board for his 3040T mentioned in my previous post. He has been unsurprisingly unsatisfied with the performance of the terrible old SFF P4 box he has been using to drive it with LinuxCNC, and we’ve (read: I’ve) become reasonably comfortable with grbl due to the several shitty diode laser cutters that have recently proliferated around here (One or more of the involved parties will be posting about those shortly). As I’ve noted elsewhere, grbl is not my first choice, but has reached baseline required functionality in versions >1.1 and is unarguably convenient.

In particular, he went with one of the Arduino Nano based boards floating around ebay with titles like USB 3-Axis CNC TB6560 Driver Board Controller Converter GRBL Arduino Nano DB25, which are unfortunately both undocumented and (as it turns out) unsuitable. He asked me to help set it up, and this post serves to document and warn based on my findings.

It seems like it should be a great solution, but it will not work with the typical black control boxes that come with many little aluminum CNC machines or most other common 3 or 4 axis breakout boards. It has the (dead) URL www.getlofi.com/grbl-to-3axis on the silkscreen, and while getlofi.com does appear to be a valid page run by some hackers mostly into circuit bending, I couldn’t shake any mention, much less relevant documentation out of the page. What I did find with a continuity tester and some patience is the following unfortunate arrangement:

The problem is that the designer decided to tie DB25 pins 2,6,and 14 together to nano pin 11 (D8) with traces on the adapter. This renders it completely unusable with the 2-7 StepX/DirX/StepY/DirY/StepZ/DirZ pinout the vast majority of boards use, as StepX and StepZ are wired together. If I’m inferring which shitty blue TB6560 3-axis board it’s designed to work with correctly, 2, 6, and 14 are intended to be per-axis stepper enable pins, but that is not a particularly common configuration.

For contrast, I picked up one of the Arduino GRBL to DB25 CNC Shield Kits available from “Ron” on Tindie to throw in my parts bin for testing. It’s actually documented, supports the pin-out most parallel control boards I’ve encountered use (with the default grbl pinout no less), and has each individual pin broken out like a sane designer, so it should support any reasonable configuration. I tried my tindie board with the machine that was supposed to get the fail board, and it seems to work fine, so I’m going to encourage picking up one of those instead (unless we get ambitious and just cut our own DB25-Nano board).

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