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Building a Pressure-Sensitive, Multi-Point TouchScreen?
sonamchauhan asks: "I'd like advice on building (yes, building) my own low-res touchscreen. The reasons for 'build' instead of 'buy' are: 1) to have it sense pressure (pressure sensing is quite expensive) and 2) to have it sense multiple points of contact simultaneously (which is a useful thing). Back in 1985, researchers at U.Toronto built (PDF file) a touch-tablet (not a touch-screen) that fulfilled both requirements (pressure-sensitive and multi-touch) and used only basic electronics: lots of diodes, A/D convertors, etc. Some 17 years later, it should be possible to build a touch-screen using the same techniques (possibly using layers of transparent conductive and insulating paint for the sensor paths.) Any comments? Some other links: a Microsoft paper (PDF file) describing a touch sensor painted onto a mouse, a basic FAQ on current touchscreen technology, and a slashdot thread that discussed building touchscreens (these links don't address pressure or multi-touch though)."
Can't you people think of something other than porn?
Friends don't let friends use multiple inheritance.
The first thing you're going to need is a Pressure-Sensitive, Multi-Point TouchScreen. Once you've got that, problem solved.
Got friends?
What better way of demonstrating this than by looking at the hidden messages contained within the names of some of Linux's most outspoken advocates:
I'm sure that Eric S. Raymond, composer of the satanic homosexual propaganda diatribe The Cathedral and the Bizarre, is probably an anagram of something queer, but we don't need to look that far as we know he's always shoving a gun up some poor little boy's rectum. Update: Eric S. Raymond is actually an anagram for secondary rim and cord in my arse. It just goes to show you that he is indeed queer.
Update the Second: It is also documented that Evil Sicko Gaymond is responsible for a nauseating piece of code called Fetchmail, which is obviously sinister sodomite slang for 'Felch Male' -- a disgusting practise. For those not in the know, 'felching' is the act performed by two perverts wherein one sucks their own post-coital ejaculate out of the other's rectum. In fact, it appears that the dirty Linux faggots set out to undermine the good Republican institution of e-mail, turning it into 'e-male.'
As far as Richard 'Master' Stallman goes, that filthy fudge-packer was actually quoted on leftist commie propaganda site Salon.com as saying the following: 'I've been resistant to the pressure to conform in any circumstance,' he says. 'It's about being able to question conventional wisdom,' he asserts. 'I believe in love, but not monogamy,' he says plainly.
And this isn't a made up troll bullshit either! He actually stated this tripe, which makes it obvious that he is trying to politely say that he's a flaming homo slut!
Speaking about 'flaming,' who better to point out as a filthy chutney ferret than Slashdot's very own self-confessed pederast Jon Katz. Although an obvious deviant anagram cannot be found from his name, he has already confessed, nay boasted of the homosexual perversion of corrupting the innocence of young children. To quote from the article linked:
'I've got a rare kidney disease,' I told her. 'I have to go to the bathroom a lot. You can come with me if you want, but it takes a while. Is that okay with you? Do you want a note from my doctor?'
Is this why you were touching your penis in the cinema, Jon? And letting the other boys touch it too?
We should also point out that Jon Katz refers to himself as 'Slashdot's resident Gasbag.' Is there any more doubt? For those fortunate few who aren't aware of the list of homosexual terminology found inside the Linux 'Sauce Code,' a 'Gasbag' is a pervert who gains sexual gratification from having a thin straw inserted into his urethra (or to use the common parlance, 'piss-pipe'), then his homosexual lover blows firmly down the straw to inflate his scrotum. This is, of course, when he's not busy violating the dignity and copyright of posters to Slashdot by gathering together their postings and publishing them en masse to further his twisted and manipulative journalistic agenda.
Sick, disgusting antichristian perverts, the lot of them.
In addition, many of the Linux distributions (a 'distribution' is the most common way to spread the faggots' wares) are run by faggot groups. The Slackware distro is named after the 'Slack-wear' fags wear to allow easy access to the anus for sexual purposes. Furthermore, Slackware is a close anagram of claw arse, a reference to the homosexual practise of anal fisting. The Mandrake product is run by a group of French faggot satanists, and is named after the faggot nickname for the vibrator. It was also chosen because it is an anagram for dark amen and ram naked, which is what they do.
Another 'distro,' (abbrieviated as such because it sounds a bit like 'Disco,' which is where homosexuals preyed on young boys in the 1970s), is Debian, an anagram of in a bed, which could be considered innocent enough (after all, a bed is both where we sleep and pray), until we realise what other names Debian uses to describe their foul wares. 'Woody' is obvious enough, being a term for the erect male penis, glistening with pre-cum. But far sicker is the phrase 'Frozen Potato' that they use. This filthy term, again found in the secret homosexual 'Sauce Code,' refers to the solo homosexual practice of defecating into a clear polythene bag, shaping the turd into a crude approximation of the male phallus, then leaving it in the freezer overnight until it becomes solid. The practitioner then proceeds to push the frozen 'potato' up his own rectum, squeezing it in and out until his tight young balls erupt in a screaming orgasm.
And Red Hat is secret homo slang for the tip of a penis that is soaked in blood from a freshly violated underage ringpiece.
The fags have even invented special tools to aid their faggotry! For example, the 'supermount' tool was devised to allow deeper penetration, which is good for fags because it gives more pressure on the prostate gland. 'Automount' is used, on the other hand, because Linux users are all fat and gay, and need to mount each other automatically.
The depths of their depravity can be seen in their use of 'mount points.' These are, plainly speaking, the different points of penetration. The main one is obviously
More evidence is in the fact that Linux users say how much they love `man`, even going so far as to say that all new Linux users (who are in fact just innocent heterosexuals indoctrinated by the gay propaganda) should try out `man`. In no other system do users boast of their frequent recourse to a man.
Other areas of the system also show Linux's inherit gayness. For example, people are often told of the 'FAQ,' but how many innocent heterosexual Windows users know what this actually means. The answer is shocking: Faggot Anal Quest: the voyage of discovery for newly converted fags!
Even the title 'Slashdot' originally referred to a homosexual practice. Slashdot of course refers to the popular gay practice of blood-letting. The Slashbots, of course are those super-zealous homosexuals who take this perversion to its extreme by ripping open their anuses, as seen on the site most popular with Slashdot users, the depraved work of Satan, http://www.eff.org/.
The editors of Slashdot also have homosexual names: 'Hemos' is obvious in itself, being one vowel away from 'Homos.' But even more sickening is 'Commander Taco' which sounds a bit like 'Commode in Taco,' filthy gay slang for a pair of spreadeagled buttocks that are caked with excrement. (The best form of lubrication, they insist.) Sometimes, these 'Taco Commodes' have special 'Salsa Sauce' (blood from a ruptured rectum) and 'Cheese' (rancid flakes of penis discharge) toppings. And to make it even worse, Slashdot runs on Apache!
The Apache server, whose use among fags is as prevalent as AIDS, is named after homosexual activity -- as everyone knows, popular faggot band, the Village People, featured an Apache Indian, and it is for him that this gay program is named.
And that's not forgetting the use of patches in the Linux fag world -- patches are used to make the anus accessible for repeated anal sex even after its rupture by a session of fisting.
To summarise: Linux is gay. 'Slash -- Dot' is the graphical description of the space between a young boy's scrotum and anus. And BeOS is for hermaphrodites and disabled 'stumpers.'
FEEDBACK
Well, the only reason I know all about this is because I had the misfortune to read the Linux 'Sauce code' once. Although publicised as the computer code needed to get Linux up and running on a computer (and haven't you always been worried about the phrase 'Monolithic Kernel'?), this foul document is actually a detailed and graphic description of every conceivable degrading perversion known to the human race, as well as a few of the major animal species. It has shocked and disturbed me, to the point of needing to shock and disturb the common man to warn them of the impending homo-calypse which threatens to engulf our planet.
Doesn't it give you a hard-on to imagine your thick strong poker ramming it's way up my most sacred of sphincters? You're beyond help, my friend, as the only thing you can imagine is the foul penetrative violation of another man. Are you sure you're not Eric Raymond? The government, being populated by limp-wristed liberals, could never stem the sickening tide of homosexual child molesting Linux advocacy. Hell, they've given NAMBLA free reign for years!
Thank you for your kind words of support. However, this document shall only ever be posted anonymously. This is because the 'Open Sauce' movement is a sham, proposing homoerotic cults of hero worshipping in the name of freedom. I speak for the common man. For any man who prefers the warm, enveloping velvet folds of a woman's vagina to the tight puckered ringpiece of a child. These men, being common, decent folk, don't have a say in the political hypocrisy that is Slashdot culture. I am the unknown liberator.
We shouldn't hate them, we should pity them for the misguided fools they are... Fanatical Linux zeal-outs need to be herded into camps for re-education and subsequent rehabilitation into normal heterosexual society. This re-education shall be achieved by forcing them to watch repeats of Baywatch until the very mention of Pamela Anderson causes them to fill their pants with healthy heterosexual jism.
Well, it just goes to show that even the holy Linux 'sauce code' is riddled with bugs that need fixing. (The irony of Jon Katz not even being able to inflate his scrotum correctly has not been lost on me.) The Linux pervert elite already acknowledge this, with their queer slogan: 'Given enough arms, all rectums are shallow.' And anyway, the PS2 sucks major cock and isn't worth the money. Intellivision forever!
For one thing, whilst Linux is a cavalcade of queer propaganda masquerading as the future of computing, NT is used by people who think nothing better of encasing their genitals in quick setting plaster then going to see a really dirty porno film, enjoying the restriction enforced onto them. Remember, a wasted arousal is a sin in the eyes of the Catholic church. Clearly, the only god-fearing Christian operating system in existence is CP/M -- The Christian Program Monitor. All computer users should immediately ask their local pastor to install this fine OS onto their systems. It is the only route to salvation.
Secondly, this message is for every man. Computers know no colour. Not only that, but one of the finest websites in the world is maintained by a Black Man . Now fuck off you racist donkey felcher.
Although there is nothing unholy about the fine heterosexual act of ejaculating between a woman's breasts, squirting one's load up towards her neck and chin area, it should be noted that Perl (standing for Pansies Entering Rectums Locally) is also close to 'Pearl Monocle,' 'Pearl Nosering,' and the ubiquitous 'Pearl Enema.'
One scary thing about Perl is that it contains hidden homosexual messages. Take the following code: LWP::Simple -- It looks innocuous enough, doesn't it? But look at the line closely: There are two colons next to each other! As Larry 'Balls to the' Wall would openly admit in the Perl Documentation, Perl was designed from the ground up to indoctrinate it's programmers into performing unnatural sexual acts -- having two colons so closely together is clearly a reference to the perverse sickening act of 'colon kissing,' whereby two homosexual queers spread their buttocks wide, pressing their filthy torn sphincters together. They then share small round objects like marbles or golfballs by passing them from one rectum to another using muscle contraction alone. This is also referred to in programming 'circles' as 'Parameter Passing.'
And PHP stands for Perverted Homosexual Penetration. Didn't you know?
Well, I don't know about terraforming Mars, but I do know that homosexual Linux Advocates have been probing Uranus for years.
*sniff* That brings a tear to my eye. Thank you once more for your kind support. I have taken faith in the knowledge that I am doing the Good Lord's work, but it is encouraging to know that I am helping out the common man here.
However, I should be cautious about revealing your name 'Cerberus' on such a filthy den of depravity as Slashdot. It is a well known fact that the 'Kerberos' documentation from Microsoft is a detailed manual describing, in intimate, exacting detail, how to sexually penetrate a variety of unwilling canine animals; be they domesticated, wild, or mythical. Slashdot posters have taken great pleasure in illegally spreading this documentation far and wide, treating it as an 'extension' to the Linux 'Sauce Code,' for the sake of 'interoperability.' (The slang term they use for nonconsensual intercourse -- their favourite kind.)
In fact, sick twisted Linux deviants are known to have LAN parties, (Love of Anal Naughtiness, needless to say.), wherein they entice a stray dog, known as the 'Samba Mount,' into their homes. Up to four of these filth-sodden blasphemers against nature take turns to plunge their erect, throbbing, uncircumcised members, conkers-deep, into the rectum, mouth, and other fleshy orifices of the poor animal. Eventually, the 'Samba Mount' collapses due to 'overload,' and needs to be 'rebooted.' (i.e., kicked out into the street, and left to fend for itself.) Many Linux users boast about their 'uptime' in such situations.
If only indeed. You can help our brave cause by moderating this message up as often as possible. I recommend '+1, Underrated,' as that will protect your precious Karma in Metamoderation. Only then can we break through the glass ceiling of Homosexual Slashdot Culture. Is it any wonder that the new version of Slashcode has been christened 'Bender'???
If we can get just one of these postings up to at least '+1,' then it will be archived forever! Others will learn of our struggle, and join with us in our battle for freedom!
I am compelled to document the foulness and carnal depravity that is Linux, in order that we may prepare ourselves for the great holy war that is to follow. It is my solemn duty to peel back the foreskin of ignorance and apply the wire brush of enlightenment.
I could make an arrogant, childish comment along the lines of 'Every time someone asks for 2.0, I won't release it for another 24 hours,' but the truth of the matter is that I'm quite nervous of releasing a 'number two,' as I can guarantee some filthy shit-slurping Linux pervert would want to suck it straight out of my anus before I've even had chance to wipe.
I sincerely hope you're Natalie Portman.
What the fuck?
Well bugger me!
Fuck right off!
IMPORTANT: This message needs to be heard (Not HURD, which is an acronym for 'Huge Unclean Rectal Dilator') across the whole community, so it has been released into the Public Domain. You know, that licence that we all had before those homoerotic crypto-fascists came out with the GPL (Gay Penetration License) that is no more than an excuse to see who's got the biggest feces-encrusted cock. I would have put this up on Freshmeat, but that name is known to be a euphemism for the tight rump of a young boy.
Come to think of it, the whole concept of 'Source Control' unnerves me, because it sounds a bit like 'Sauce Control,' which is a description of the homosexual practice of holding the base of the cock shaft tightly upon the point of ejaculation, thus causing a build up of semenal fluid that is only released upon entry into an incision made into the base of the receiver's scrotum. And 'Open Sauce' is the act of ejaculating into another mans face or perhaps a biscuit to be shared later. Obviously, 'Closed Sauce' is the only Christian thing to do, as evidenced by the fact that it is what Cathedrals are all about.
Contributors: (although not to the eternal game of 'soggy biscuit' that open 'sauce' development has become) Anonymous Coward, Anonymous Coward, phee, Anonymous Coward, mighty jebus, Anonymous Coward, Anonymous Coward, double_h, Anonymous Coward, Eimernase, Anonymous Coward, Anonymous Coward, Anonymous Coward, Anonymous Coward, Anonymous Coward, Anonymous Coward, Anonymous Coward, Anonymous Coward. Further contributions are welcome.
Current changes: This version sent to FreeWIPO by 'Bring BackATV' as plain text. Reformatted everything, added all links back in (that we could match from the previous version), many new ones (Slashbot bait links). Even more spelling fixed. Who wrote this thing, CmdrTaco himself?
Previous changes: Yet more changes added. Spelling fixed. Feedback added. Explanation of 'distro' system. 'Mount Point' syntax described. More filth regarding `man` and Slashdot. Yet more fucking spelling fixed. 'Fetchmail' uncovered further. More Slashbot baiting. Apache exposed. Distribution licence at foot of document.
- posted by poopbot: lovely snot! wonderful snot!
QZU6EftJQG Post #809
I would think that the time and effort that went into developing something like this, basically from scratch, would outweigh the "real" cost savings of not buying one off-the-shelf. I suppose if this is just for fun, than that's not really a concern, but if your time is worth anything at all, it ought to be considered.
I don't know how feasible this is, but couldn't one use LEDs in the screen frame along with detectors opposite arranged so that they form a detection grid on the surface of the screen and register an interruption of the light (such as by touch or something)?
In theory, there is no difference between theory and practice. In practice, there is.
This place stinks worse than the month-old smegma I dug out from under my cock-skin today. Wooooowheeeee!! Taco, quit creaming on the server and letting it ferment. JESUS!
Hey, kid... wanna touch my "kernel patch"?
-- Alan Cox
1- have the slashdot community provide plans for a pressure-sensitive multi-point touchscreen
2- ??????????
3- profit!!
Do you want the touch points to be able to detect different pressures, or just on or off? In either case, do you want to be able to detect all points on the screen at once, or just a lot?
Last post
First, is it ok to use a stylus? If so, you're problem just got easier - you simply use the same technology that wacom uses, except you'll need to track several pens instead of one.
I'm betting, though, that you want a real 'touch' screen which registers anything hitting the surface.
Here's what you do: Use a transparent metalization process to put squares of transparant, conducting (but resistive) metal on two opposing pieces of plastic. Take a wire from each square and use a microprocessor with a lot of i/o (switched A/D converters, most likely) to detect which metal plates are being pushed together. The size of the plates determines resolution.
That's the easy, no brainer way.
The cool way (with infinite resolution ) is to use the normal method modified a bit. Normally you have two sheets covered with resistive material, one which has conductors on the vertical sides and one with conductors on horizontal sides. Increase the conductors (say, four shorter conductors on each side, and make them points instead of lines).
Send a signal to one conductor, and listen to all the other conductors for the wave front of the returning signal. Through a ton of signal processing (and sending signals from the others and measuring the response) you'll be able to detect an arbitrary number of points on the screen. You'll need to do a lot more processing to measure surface area (pressure), but you'll get there eventually.
Alternately, you get rid of it entirely and make a video system that can sense the position and movement of your hand and get rid of the 'touchyfeely' altogether. This (IMHO) would be easier and faster to develop.
-Adam
From a whole lot of research I have been involved in, for a while we worked with a company, TacTex Controls Inc.
They have a pressure sensative pad and system you can use, the MTC Express (http://www.tactex.com/prodMTC.htm), however, that is not where you would be interested directly.
Their technology uses fiberoptics in a rubber pad with a small controller. There is a lot of research in integrating their technolgies into other things (a prototype of a complete pressure sensative suit was discussed at one stage).
It fufills your requirements quite well.
256 levels of pressure for each region of the pad independently.
The MTC Express pad had only a DB9 serial connection, and needed a power input as well. However, the OEM material and controllers were a lot more flexible in usage.
ICQ# : 30269588
"I used to be an idealist, but I got mugged by reality."
They go like this:
1. Get the slashdot community (which includes myself) to provide plans for a pressure-sensitive, multi-point touchscreen.
2. Build one as a component for my project.
3. Taiwanese/Chinese/American/.... manufacturers notice the plans on slashdot.org
4. Cheap pressure-sensitive multi-point touchscreen become available.
Hi! I'm trying to avoid a stylus in favor of just using fingers (which is why the screen only needs to be low-res).
> you have two sheets covered with resistive
> material, one which has conductors on the
> vertical sides and one with conductors on
> horizontal sides. Increase the conductors (say,
> four shorter conductors on each side, and make
> them points instead of lines).
Actually, I was looking at using something similar to the circuit in the U.Toronto paper. That circuit seems to require only one layer of sensors that sense touch and pressure by measuring capacitance at the point being touched. I think this method also provides infinite resolution.
I was thinking on the lines of using this idea and painting-on the sensors to the screen with transparent conductive paint. Another layer of transparent insulating paint would cover the track upto the sensor point.
You know about these guys:
http://www.fingerworks.com/
right? They've been mentioned on Slashdot before. Their products can detect multiple fingers at once.
They are selling tablets and keyboard replacements, not touchscreens, but I think I read somewhere (on their website maybe) that they believe it would be possible some day to use this tech in a touchscreen.
The cool thing is it sees your whole hand via infrared, so it can tell which finger you're using. For the first time, you can "right click" on a touch surface, or use other finger combinations/gestures for various operations (drag, pan/scroll, rotate, etc.)
If not, you might think about using a standard touch screen system, then building (or buying, if they exist - probably don't) pressure sensitive "gloves". For the sensors (at the finger tips), buy thin ribbon plastic tubing (multiple tubes joined in a ribbon - used in many continuous ink kits for ink-jet printers, so you should be able to buy it somewhere by itself), spread one end and seal the ends of each tube, apply gentle heat and blow "bubbles" at the end of each tube (this may be difficult, but not impossible). Then, attach these bubbles to the fingertips of the gloves, and use a T-connector on the other end of the cable to hook the tubing to a very low pressure air supply and the other side of the T-connector to a air-pressure transducer. Hook the transducers up to a PIC or Stamp (or other ADC system) to measure the pressure change (the positive pressure keeps the bubbles inflated at all times, and reinflates them after being depressed - a closed system might work too, with no active pressurisation - you might have to experiment here).
Other cool things to do with the gloves:
1. Touch gestures (like a chorded keyboard)
2. Use water instead of air, then warm or cool the water with a peltier to provide feedback.
3. Pulse the pressure for other feedback needs.
Hope this helps...
Reason is the Path to God - Anon
> . A touchscreen with hundreds of tiny
> etched "wires" across the inside of two
> surfaces that "connect" when you touch can get
Just as an aside: the most efficient 'layer' to build this would be LCD display manufacturers. The way I see it, they already adress each pixel individually to output data (light); they could do the same to input data (pressure).
Here's an idea: You know that a sheet of plastic behaves somewhat like a fibre-optic channel, so that when you shine light in one side, it is easily visible on the other side, but doesn't interfere with just looking right through the plastic.
However, if you press on the plastic, deforming it, then the light can be seen around your finger, because now you have a sharper angle of incidence in the plastic. My idea is to take a thin sheet of plastic (eg. overhead transparency), put it over top of a flexible substrate (a gel or something like that), then shine LEDs in one edge of it, and look at the amount of light on the other edge (using eg. photo diodes and A/D inputs). This may give you an indication of absolute pressure as well.
When you press on the plastic, the sensors in line with your finger will have a reduced (or maybe increased?) amount of light. Anyways, you will be able to find the center of the disturbance. Do this both vertically and horizontally, and it looks like you have a touch screen!
This can't sense more than one input point simultaneously because you just get two horizontal readings and two vertical readings, but maybe you could use an idea which has already been suggested and remember which of the two locations was pressed first. This may not work in the pathological cases, but what the heck...
Another alternative way to solve the problem is with proximity sensing behind the screen (I guess this wouldn't work for CRTs). Proximity sensing is done (for body parts) by detecting the water in people's hands. This increases the effective capacitance of two plates side by side. Then you need an oscillator circuit which goes from stability to instability as you change this capacitance. You would probably need a bunch of these circuits, so this is more difficult than my other idea.
Anyone else have ideas what this could be used for?
Slashdot: rejecting tech news in favor of rubber band guns since 1997.