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A Minimum Viable Computer, or Linux for $15

bbenchoff.github.io

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Re: A Minimum Viable Computer, or Linux for $15

#401

Post by webmaven »

kragen wrote: post #400
webmaven wrote: post #399

Earlier quoted context omitted.

> I think I've mostly watched resin casting demonstrations by very experienced people, so I may have unreasonably positive expectations of what is possible, but I think it's fairly common for art students to get some successful resin casts in a single-semester sculpture course? It is much easier to get good results with a bit of in-person guidance, and in a controlled environment. There are also optional materials (e…

Interesting, I hadn't thought of it that way! Thank you.

You're welcome. I just realized there is a bit of nuance missing from my comment. The unattractiveness of casting diminishes even if you only want one of a thing if it is the case that you will want many things rather than only one thing ever. Many of the videos on the subject seem to be of experienced makers creating many different unique objects. This does of course allow you to amortize the equipment costs across many projects, just as you can for machine tools, and the optional equipment I mentioned (whether purchased or DIY) becomes much more approachable.

Still, it is really hard to beat vacuum forming for approachability in making a one off: The only equipment you don't have laying around can be made with a few chunks of wood. If you have a small oven (even a toaster oven) that only limits the size of your parts. If you have a vacuum cleaner with crappy suction, that just means you can only form thin sheets.

BTW, all these techniques combine. In the case of resin casting, I mentioned that you really need to have made a one-off in order to create the silicone molds. In fact, I have in the past vacuum formed a blank shape (this was before 3D printing was a thing), sanded or machined it to more precise tolerances, added details (dedents, screw posts or holes, flanges, ribs, ridges, textures, etc.) and then used silicone molds and resin casting to make duplicates. Sometimes you actually do need several identical parts in order to just make one object...

Re: A Minimum Viable Computer, or Linux for $15

#402

Post by hugo82 »

miav wrote: post #222

> It costs $10,000 USD to build one of these > The ten thousandth one costs $15 As a software engineer, I'm used to being able to build essentially whatever I want, with the only cost being my time. I'm often unpleasantly reminded that software is an outlier in that regard and as soon as physical items are concerned, especially hardware, it turns out that manufacturing even a simple thing is prohibitively expensive i…

Amen. They used to say the first Space Shuttle launch of the year cost $3.5B, since that was the annual carrying cost of the non-unit costs. Got a lot cheaper after that, though never that "cheap".

Re: A Minimum Viable Computer, or Linux for $15

#403

Post by kragen »

webmaven wrote: post #401
kragen wrote: post #400

Earlier quoted context omitted.

Interesting, I hadn't thought of it that way! Thank you.

You're welcome. I just realized there is a bit of nuance missing from my comment. The unattractiveness of casting diminishes even if you only want one of a thing if it is the case that you will want many things rather than only one thing ever. Many of the videos on the subject seem to be of experienced makers creating many different unique objects. This does of course allow you to amortize the equipment costs across…

Yes! Today I bought 20 identical poorly-injection-molded T-fittings for aquarium air hose, and I was thinking about your comments. It occurred to me that the existence of injection molding strongly favors designs that have several instances of the same part, like four identical wheels or 15 identical spring clips.

In some cases I think there are materials that are a lot easier to shape to make a mold pattern than whatever you're going to make your final part out of. Wood is the traditional choice, except that wax is the even more traditional choice, and clay, styrofoam, foamed waterglass, and pumice also come to mind. I guess in theory polycaprolactone might work, too, and as you say, poly(lactic acid) is a popular modern choice, sometimes painted or sanded to smooth out the print lines. And I've been wondering if it's feasible to strengthen aluminum foil by spray-painting or cathodic mineral deposition in order to make such one-off items, because aluminum foil is very easy to form, usually too easy. Lots of stuff to try!

Re: A Minimum Viable Computer, or Linux for $15

#404

Post by andi999 »

lkois wrote: post #339
lazide wrote: post #321

Earlier quoted context omitted.

Just wait until it’s machining! Wood working at least most of the time tolerances are +- 1/8”. Throwing away a thousand dollar part because you were .003” off is lame. At least if you have a grinder, welding can sometimes be more forgiving.

Oof, I used to work with one of the few workshops in the world that could produce small batches of parts down to 0.0001mm or something a bit ridiculous. Their pricing and supply times factored in a pretty significant failure rate, and we were basically asking them for highly precise screws and nuts for a couple thousand each.

For what application would one need such a precision?

Re: A Minimum Viable Computer, or Linux for $15

#405

Post by kwhitefoot »

mmanulis wrote: post #101
kwhitefoot wrote: post #74

Earlier quoted context omitted.

Surely an ESP32 should be able to run Linux. Then you would get Bluetooth and Wi-Fi. After all Linux used to run on 486, BSD ran on 386.

Kind of: https://hackaday.com/2021/07/21/its-linux-but-on-an-esp32/ Main issue with Linux on an MC is lack of MMU, though YMMV

There have been Linux distributions that ran on machines without MMU. For instance μClinux, see https://en.wikipedia.org/wiki/%CE%9CClinux

Re: A Minimum Viable Computer, or Linux for $15

#406

Post by antoinealb »

Teknoman117 wrote: post #385
aidenn0 wrote: post #378

Earlier quoted context omitted.

"Easier than QFN" isn't a glowing recommendation but makes me hopeful. QFNs are the bane of my existence.

I should mention, when I did QFNs, I used solder paste, a stencil, and a hotplate. I don't think I could ever manage to hand solder one. Passives on the backside were done with solder paste, a stencil, and a hot air reflow station.

Do you have a reference to a hotplate you like for QFN? I have been considering one because I just don't get good results with hot air, and a reflow oven seems like a bit too much for my use case.

Re: A Minimum Viable Computer, or Linux for $15

#407

Post by kragen »

stragies wrote: post #398
kragen wrote: post #293

Earlier quoted context omitted.

How easy is it to patch its kernel?

It would seem a mainline linux kernel can run everything apart from the camera on (Redmi 2) SnapDragon 410: https://wiki.postmarketos.org/wiki/MSM8916_Mainlining

That's good news! I was thinking more about the question of locked bootloaders. Having to patch an outdated kernel is a lot less serious than not being able to run any kernel you've patched. https://forum.xda-developers.com/t/redmi-2-prime-bootloader-... suggests that maybe the Redmi 2 comes with an unlocked bootloader?

Re: A Minimum Viable Computer, or Linux for $15

#408

Post by lkois »

andi999 wrote: post #404
lkois wrote: post #339

Earlier quoted context omitted.

Oof, I used to work with one of the few workshops in the world that could produce small batches of parts down to 0.0001mm or something a bit ridiculous. Their pricing and supply times factored in a pretty significant failure rate, and we were basically asking them for highly precise screws and nuts for a couple thousand each.

For what application would one need such a precision?

International standards for reference connectors for medical devices. Basically, if you make syringes or IV lines with a screw fitting, the dimensions of that fitting need to be within some range so it'll make a secure connection to something else. Those are made out of plastic, all materials and dimensions are well defined for their usage and mass production, and have a decent tolerance to them.

But to check THAT tolerance, you have these metal screws that they need to securely attach or be unable to attach to. And since the metal fittings will be used for batch testing entire production runs of life or death parts for years to come, they go a little overboard with specifications.

I'm not sure if it really needed to be THAT precise, but that's just what it was

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