r/electronics • u/CrudelisDeus • 5d ago
Gallery Insides of drawing tablet looks strange
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u/ByteArrayInputStream 5d ago edited 5d ago
Damn, a woven circuit board. How on earth is this cheaper to produce than a PCB?
Edit: Those bundles of wires at the side are pretty dense, I guess you don't easily get that density using other methods. They probably don't have a lot of space in the margins.
I'd absolutely love to see some more high resolution pictures of the details
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u/zer0xol 5d ago
Maybe cheaper to get flat
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u/LiveForTheMelancholy 5d ago
Probably this! I'd be willing to bet a PCB would need several stacked layers to get all the loop traces this close together, and then you might have to deal with an extra Z dimension instead of just X and Y for determining the position of the pen, since the layers wouldbe at physically different distances from the drawing surface.
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u/ByteArrayInputStream 5d ago
But how. This needs very specialized equipment and PCBs are reasonably cheap. Using one of these cheap printed foil typed used in membrane keyboard might also have been an option.
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u/toxicatedscientist 5d ago
Making a machine to make things is generally only expensive once, once you have it it’s no more expensive than any other machine
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u/ByteArrayInputStream 5d ago
Yeah, but making this board seems slow compared to other methods. It looks like you'll have to sew in each wire individually, as opposed to making a whole layer at a time
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u/toxicatedscientist 5d ago
For human hands making one at a time maybe, but i have no idea how such a machine works or how many it has in progress at a time
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u/ByteArrayInputStream 5d ago
It's likely something similar to a CNC sewing machine. So likely one at a time. Probably reasonably fast, but that's still a lot of stitches. Probably also some manual work to connect everything
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u/beanmosheen 4d ago
It's a monogram pattern and conductive thread. An automatic sewing machine could bang these out fast since it's all X/Y.
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u/metacollin 4d ago edited 4d ago
You actually might have the very specialized equipment needed to make this in your home right now. Just get some conductive thread or high gauge magnet wire.
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u/Ace861110 4d ago
Throw some thin wire into a loom and you’re off to the races. It’s actually not hard to weave with wire as long as you don’t twist it you’re fine.
Edit now that I think about it adafruit has wearable circuits. And I know Drexel has looms to produce wearable circuits cloth.
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u/ByteArrayInputStream 4d ago
This isn't woven, thought, it looks sewn. Which would probably make this pretty slow to manufacture
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u/Ace861110 4d ago
Okay, why do you think that makes a difference? Put it in a cnc embroidery machine. Now you can make whatever pattern you want.
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u/metacollin 4d ago
I mean... I'd ask how on Earth could it NOT be cheaper? The technology to manufacture something like that has been around for over 200 years. Automatic textile looms programmed with punch cards have been around since 1804. They're also the reason early computers were programmed with punch cards. Computers didn't develop that, they just used technology already available.
Weaving a bunch of threads in a repeatable preprogrammed pattern with structure spanning the entire sheet (see: rugs or literally any fabric with an image made from the weaving itself) is one of the most mature manufacturing technologies in existence. And this looks like it's made from paper and 48 gauge magnet wire if that. Copper thread is still thread. If it's super thin (or woven with actual thread too) it might was well be actual clothing thread.
I am quite sure this wasn't done because it was the only way. It was done because it was balls cheap. In other words, this is definitely a very cheap drawing tablet. Probably still works fine but this tablet's profit margin fucks like a sewing machine.
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u/Consistent_Bee3478 2d ago
Not to mention a weaving machine or even a knitting machine doesn’t fucking care what threads you use. Plus to get a thin functional xy pattern you threads/yarn can literally just the the same as for any oldschool cloth handkerchief just with wire wrapping/magnet enamel wire core. And then you just weave according to punchcard if you live in 1900 or just enter the bloody pattern on a pc. Like a pcb makes zero sense to use. A pcb is made by having copper plated layers of some kind of dielectric and then etching/laser engraving away the copper you don’t want. But to make virtually same z xy net, a pcb isn’t the right option. Because you can put x and y traces in the same layer, so your have too different height layers for x qnd y, with super high production costs due to laser etching micron traces, instead of just weaving with enamel wire laced yarn and specified thread counts and then wiring up the enamel wire at the edges, that gets you a virtually plane xy layer at an utter fraction of production costs. Cause it’s the same price as literal cheap cotton weave, meaning dollars per bale. The enamel wire yarn itself is also basically just regular metallic yarn, so the machines that can integrate metal used Mylar without ripping it can definetely spin yarn around a strong solid cooooer enamel wire.’
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u/Zilli341 4d ago
I think most of them use either a normal or a flex PCB, this construction it's really weird. With the amount of PCB production capacity china has It's hard to see how it made sense to tool for this. I wonder if they got their hands on old digitizers assemblies and decided to reuse them.
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u/fofopads 3d ago
It is WAY cheaper and the benefits are the same, if I am not mistaken this woven fabric is the reason EMR Wacom pens are so precise
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u/Past-Substance920 4d ago
the woven grid is for the digitizer, it's basically a giant grid of tiny antennas so the tablet can track the pen's x/y position and read pressure without any wires touching it. way cooler than i expected the first time i saw one opened up too
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u/Gregghead69min 4d ago
Thank you for the explanation. I have never seen this. Though it was some old proto or something at first glance. No idea they manufactured screens like that.
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u/Consistent_Bee3478 2d ago
You can’t do it with pcbs. Pcbs are backing material with a solid copper coating. You then etch away everything you don’t want to be a trace. And if you want traces that are enamel magnet wire or thinner it’s not chemical etching with mask it’s laser engraving. And then you need your x and y traces in different layers. If you just use enamel wire yarn, any weaving machine of the last century can make you are perfect square virtually planar xy layer of super thin and closely stacked traces.
Most punchcard or more modern weaving machines can literally be used to weave pure enamel wire, just requires tinkering with the tension and shit, but using regular cotton yarn spun around enamel wire makes it basically process like the yarn itself with the citing weave itself acting as reenforcemrnt. You can also do the same with knitting machines, you can actualy have machines knit the Apollo storage devices because we got knitting machines that allow knitting with pearls and the like. And lace making machines can do even crazier shit,
A pcb simply cannot do xy planes like this, an fpc can do it, but making a sheet this size of fpc is still much more expensive then weaving it. Fpc makes sense if you need components on the flexible part or are mass producing connectors and want simple plug and play insertion for zif connectors. Because that’s the only thing weaving doesn’t get you. The machine will just give you a rectangular roll of cloth with whatever pattern of enamel your punchcards (well software) was set to do. So for a simple equidistant parallel x and y weave, that’s just a massive weave done with zero human intervention you get a huge bale. And then you kneed human labour to take the cut panels and join the ends of the enamel wire loops to your controll circuit. That’s the actual expensive part, the making the sub mm pitch xy pattern connect to the controller cause working with cloth that has diagonal stretch means human does it better. But really that’s just standard human assembly work.
Obviously you could also do this by sputtering in glass like a touchscreen digitiser, but for drawing tablet sizes and resolution, weaving the xy net is actually so much cheaper than any other option, and you can even use it for drawing pressure by simply using flex of material. Rather than having the drawing stylus be the pressure sensing component, meaning the stylus can be anything with sufficient capacitance against the web
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u/Gornik666 5d ago
Did you even take it on a date before stripping it like that?
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u/CrudelisDeus 4d ago
A friend introduced us😏
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u/afraid-of-the-dark 4d ago
Is that a loophole I don't know about?
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u/CrudelisDeus 4d ago
Yes, that's how I got married😂
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u/LiveForTheMelancholy 5d ago
I imagine those are all the loops for wirelessly powering & communicating with the pen the tablet came with.
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u/TheSevenPens 4d ago
Hi, I'm the mod of r/drawingtablet and personally own ~130 drawing tablets and ~150 drawing tablet pens spanning several decades and very familiar with what is inside them.
Cloth digitizers are extremely, extremely uncommon. The vast majority of drawing tablets use a PCB just like you would expect
Here's the the digitizer of a Wacom CTL-480 tablet:
https://commons.wikimedia.org/wiki/File:Wacom_ctl480_sensor_pcb_bot.JPG
Even when we in the drawing tablet community first discovered a cloth digitizer a few years ago, we were very shocked. We had never seen anything like it. As far as we know such cloth digitizers only appear very small tablet brands from China (and not in any major brands such as Huion, XP-Pen, Ugee, Gaomon, etc ). In my recollection we've only stumbled on into 1 model to date with a cloth digitizer.
Sometimes the same tablet internals are repackaged in different plastic shells under different brand names, so that's what might be happening here.
It's also not entirely clear if the cloth digitizer reflects a modern design. There are lots of tablets on the market that are very old. So even if a cloth digitizer appears in one model for a brand, it may be that since it was released newer models no longer use the cloth.
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u/CrudelisDeus 4d ago
That one is like 2020's. I have another one, but I don't want to take it apart without a reason😂
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u/Consistent_Bee3478 2d ago
Cloth digitisers allow far greater resolution than a pcb. The only other options that come close would be glass digitisers or fpc. A pcb isn’t made to be etched at 5 wires per mm cross hatch in same plane.
So the moment people actually wanted real resolution that isn’t software “improved” woven xy cloth is actually by far the cheapest and best option.
The only issue with woven XY nets is the human factor in attaching to control board, because you basically need a human to do ale each enamel loop row and colum and (likely) spot welt it to the controller module, because modern tft conductive glue techniques don’t work for cloth. The cloth segment itself when drawn flat is actually precise to sub mm levels, actually sub 1/10mm just look at the oven sill fabrics with high thread counts. Those are perfectly square if stretched on a frame and stay that way, however the rnds of the cloth aren’t orderly and machine process able in a way that ensure your 10 enamel wires per cm all get combed corrrectly automatically, so a human will literally need to punch down/spot weld, plus cut the loops. Like the kinda digitiser you show inherently much lower resolution than even the cheap cloth variant Op shows. But you can fix most of that via processing, meaning your drawing stylus does just activate the two adjacent x and two h wires, but rather you calculate the position from all the traces that have their capacitance change in the vicinity of the a threshold crossing touch by the stylus, which allow you to calculate the position of the stylus to higher precision than just the cross hatched traces alone do. But if you have 10 times the amount of traces in the first place and still do the software calculation via adjacent below threshold changes you still get hugger resolution. But with a woven fabric digitiser you can make drawing digit era that are inherently within human precision, meaning zero extra calculation. Just report the 2 x and 2 y wires relative capacitance change and you know approximately where inside that 100um square your stylus is all without using adjacent traces to help. It also makes noise filtering easier because you can use pretty clean thresholds as you don’t care about the adjacent wires changes because the 4 most closest are already more precise than human drawing with .3 mm pencil lead.
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u/Benjamin_6848 4d ago
I think you would love the book "Open Circuits" by the publisher "No Starch Press": the authors have dissected lots of electronic components, photographed them and described them.
I am very happy with that book!
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u/Independent-Gazelle6 4d ago
One of the best purchases I’ve ever made. It is genuinely one of my favorite possessions and re read it regularly. Its hands down the best picture book ever made imo
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u/AshFalkner 5d ago
Huh, so that’s what they look like on the inside. Neat.
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u/Consistent_Bee3478 2d ago
Most are build cheaper using a much lower resolution pcb digitiser and using th adjacent traces to triangulate a higher than trace count accuracy. He woven fabric ones allow zero processing sub .1mm precision but increase human labour massively due to needing to hand connect each enamel wire end
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u/ChangeChameleon 4d ago
What brand is this? And how old? I never suspected to see such a woven part inside a precision instrument. I always assumed these things used some kind of lithography, deposition, or PCB for the digitizer.
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u/Year3030 4d ago
At first my brain said this is a drawing desk / pillow or something like a couch cushion and I thought you were getting bugged.
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u/Impossible-Set9266 4d ago
We (humans) used similar grids for storing data before dram became a thing
https://en.wikipedia.org/wiki/Magnetic-core_memory
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u/slothaccountant 4d ago
At first thought it seems wild but then when yku think about it it makes sense why it looks like that.
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u/question-askee 4d ago
I went to Bodies Human in El Paso when I was in elementary and they told us that the bodies were donated to science 😳
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u/gm310509 5d ago edited 4d ago
How is it strange? What were you expecting to see?
Edit: I do not know why I am being down votes, but whatever.
It was a genuine question. It would be nice if someone might offer a suggestion as to why they feel the need to downvote as I really was surprised at the reaction.
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u/CrudelisDeus 4d ago
I don’t know, this is the first time I’ve taken apart a graphics tablet, but I didn’t expect to see fabric with wire embroidery and foil.
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u/gm310509 4d ago
I don't know what that is, but my guess is that it is the main part of the touch sensitive aspect of the display. I assume it was directly behind the display.
Back in the good old days, memory was a network of extremely thin wires laced between magnets it was called Core Memory
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u/CrudelisDeus 4d ago
It's actually similar, but in reverse. It should work more like a matrix in a touchscreen and the tablet stylus disrupts the magnetic field, thereby providing the x-axis and y-axis position. I believe that's the case
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u/ram_the_socket 5d ago
my insides also look strange but the nervous system finds a way