If you've got a budget of $1000 for that, have you considered getting a used 3D printer first? Some models are sold used for like 50€ (e.g. Ender 3 V2) on classified ads which hardly makes a dent in your overall budget.
This will force you to actually familiarize yourself with the processes and will allow you to make more informed decisions later?
The cost of the PCBs must be driven by assembly, right? The board itself should qualify for JLCPCB's budget offer at least: 2 layers (judging by the KiCAD-screenshot), < 100mm, HASL, nothing special about solder mask or board thickness either from the look of it.
I'm not not sure about the plated slots of the USB connector, though? Do these cost extra?
How many did you get assembled per version? Just two of the boards or all five of them? Did you try to stick to using the standard parts or extended library?
Which difference would it have made to do some work on the PCBs yourself, e.g. by soldering the through-hole connectors by hand?
Either way, it is definitely an amazing project!
Edit: as soon as any part is from the extended library, all different components (even standard ones) incur a cost for loading them into the pick and place machine, right? So minimizing number of different components is the only way of keeping the cost down, I guess.
Indeed the cost is mainly from assembly. The board itself is 2 layers, all default settings at Jlcpcb except for the color which is now black as opposed to the default green. This increases the cost of the board a bit. You can experiment with their calculator to find out more. I've ordered 5x each version, which is also the minimal order amount. I did try to stick to the standard library as much as possible but it's not easy once you go beyond standard passive components. Can't currently tell the exact difference it would made if I had soldered the THT by myself, likely not enough for me to bother. You could be right on that last part. The details on it are not as fresh in my head anymore. It is definitely true that you want to minimize the amount of different components. If you need 4k and 6k resistors you're better off buying 2x2k and 3x2k instead.
I don't know. It looks like every battery recycling facility I've seen before: piles of non-descript objects with unreadable labels, machines with unreadable signs posted on them, etc.
Anybody with piles of batteries like that needs a very powerful sprinkler system. Lithium battery fires at recycling centers have become a major problem, even with only a few lithium batteries. Search "lithium battery recycling fire".
There are deluge systems that can cope with battery fires. They're simple, but need a big water supply.
This is why this sort of industry usually ends up in places like Pakistan and Bangladesh. They’re desperate for work and don’t worry about safety or environmental pollution.
Seems like a waste of good water. Anyone with that quantity of batteries should have a large pile of sand on hand, a pre-placed giant hole in the ground, and a bulldozer to manage the job.
One of the recycling steps is dissolving the lithium in water. So they might just as well take a burning battery and just chuck it into the shredder, and then mix the burning slurry with water.
Contrary to the popular belief, lithium batteries do NOT contain enough oxygen to just keep self-burning. Most of the lithium-ion pyrotechnics is just from good old atmospheric oxygen, which oxidizes the organic electrolyte.
What lithium-ion batteries have is the ignition source that basically keeps going on and on. So once you extinguish the burning electrolyte, it just keeps reigniting.
That's interesting! I didn't realize that lithium-ion batteries were full of lithium hexafluorophosphate, or that it hydrolyzed to form HF at 70° in the presence of water. Thanks!
Yeah great idea, letting the fire rage in the ground (it provides its own oxygen) and leeching a lot of chemical waste products into the ground water :)
It was my understanding that battery fires don't go out because they are basically self fueling. You would be better served having a way to contain it until it burned itself out.
I was thinking of throwing in a game like Tetris with just accelerometer controls. That'll be after I find a job though. Numbers were actually the first things I displayed, I actually still have all the code to display them still sitting unused.
Text has been less of a success. Having the letters be easily legible takes more space than I would have thought, and the small pixel fonts don't look great with the big spacing between the LEDs. Maybe some scrolling text would look good, but I haven't focused on it too much. I tried getting a QR code displayed, but it didn't want to scan.
For buttons, I'm kind of married to the idea of no buttons. The accelerometer does recognize clicks and double clicks in different directions, so that might be useful for something.
I encourage anyone who wants to fork/contribute/post issues on this to do so and I'll try to be a good maintainer.
Thanks for the detailed reply. I actually like the idea of using the accelerometer as input device and the design choice of using no buttons.
What’s the update rate of the LED matrix if I may ask? Maybe the combination of an accelerometer and the LEDs lends itself to a persistence of vision display?
Are you saying that the local merchant tests it and that's why they sell it at 250x the price?
I said 10$, but it depends on the length. So 60cm is maybe 10$, 70cm is 12$, 80cm is 13.50. So you would say that testing the 70cm variant of the zipper is worth 2$ more than testing the paint on the 60cm variant?
My point is that at this price, if I don't get the zipper on Temu, I don't get it at all. I won't pay 10$ for a zipper of this quality.
I've noticed a similar 'this profit margin seems almost vulgar' on the same store shelf.
As you showed with slightly longer zippers.. I notice with car fob remote batteries. An 8 pack is $12 at the store. The same brand, a single will be $5. A 2pack is $7. And the 8pack $12.
Do you really need to make $4 on selling me a single? I know shelf space is valuable, but the same store sells things for $1 too on another shelf so apparently <$1 profit shelf space is possible.
Given how small the batteries are, they probably have similar costs for shipping and handling. So there's a cost to get _anything_ to the local store, plus the cost of the actual goods.
Open the experiment animation and refresh the page multiple times to refresh the countdown while looking at the white pixel (from the same point of view) to get an even more impressive effect.
It's common for medical articles posted here to have a great-sounding breakthrough in their title, and you then have to read the article to find out it's only been done in mice. "en-mice'd/en-micing" is a term for mods editing titles, here :D
Lay people act like this is a trump card but this is just how science is done. You can't really perform this in humans without having some data that it may very well work. Mice have been pretty good models for cancer biology. Nature Biotechnology is also a good and selective journal.
I agree, I'm just mentioning it re: clickbait titles (not calling anyone out) vs. "oh, [xyz] hasn't been cured, there's just some promising results in mice"
Well, the actual title is "Sensitization of tumours to immunotherapy by boosting early type-I interferon responses enables epitope spreading." This is just the reduced version for mass consumption. Keep in mind many people got a C in high school biology.
Checkpoint inhibitors (which are the primary driver of improved cancer treatment over the last 15 years and generate > $50B/year in sales) generally don't look very good preclinically. Even their clinical data can be hard to interpret prior to a large scale trial, which led to them almost being shelved.
The catch here is that only two targets (PD(L)-1 and CTLA-4) turned out to work well in humans. All of the other immunotherapies that looked mediocre preclinically turned out to also be mediocre or entirely ineffective in humans.
This is the nature of research pipelines. If you ask: out of all the clinical trials that have shown promise in early human trials, what percent lead to successful drugs for humans: the answer is a very small percent.
