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- Опубліковано 15 вер 2024
- Dave tears down and investigates a Dell infrared IR optical touch screen monitor found in the dumpster.
Infrared touch screen are not often used in consumer computer monitor applications compared to resistive and capacitive touch screen technologies.
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#Teardown #Infrared #Touchscreen
I want equal access to Dave's dumpsters.
No problem. Cheapest place for rent in the complex is about $15k a year.
@@EEVblog But that's in Aussie dollars, in Yankie bucks, it's about $20 :)
@@EEVblog that isn’t too bad a price. Now if only i was Australian...
@@EEVblog Since it appears that $30K is dumped there yearly, SOLD!
@Arpad Toth in tech complexes, they share E-Waste containers
At my company we got our own containers for E-waste, that only certain people have access too, because copper and gold is expensive :D
🐞They are great until a fly lands on the screen and starts walking around 'clicking' things and dragging files around! (from experience) 😣
This is not a bug - it's a feature :D
Hahaha I can totally see that happen lol.
So this is the glitch in Michigan and Wisconsin lol.
@@voltare2amstereo Dragonfly sus haha
I suppose one way to fix this problem is to have multiple stacked sensor zones, then you ignore objects which only appear in one layer.
I was also thinking you could exclude touches which are too long in duration, but that doesn't address clicking when the fly first lands.
I worked on the firmware for similar optical touchscreens back in the 2008-2012, but I dont think it was this one. Going to higher number of cameras helped in several ways. First we had to meet the new 10 touch requirements for Windows and with only 2 cameras those touches were very easily occluded by the other fingers etc, so having more triangulation's meant the points didn't have to coast in the Kalman filter/particle filter for so long. Also as you found tracking something close or far away is really hard with just 2 cameras as there is lots of reflection or basically no shadow, so getting more cameras around the screen meant you normally got a better touch signal. There were some other benefits to multiple cameras like redundancy and getting away with dead zones from dust etc.
Pffft! More cameras! Just use TruRange bro =P Good times othane...
@@tkirker61 haha forgot about that one ... Who dis ?
At an old job I recall one time at the bar a fly landed on the POS cash machine screen. The fly ordered himself a sandwich and two drinks. It was an IBM POS model which must have been infrared optical touch.
At least that fly had his priorities straight in life!
My sister has such a touchscreen and indeed when a fly lands on it, it steals the cursor 🤣
Which is why POS always ends up meaning "Piece Of S--t" :)
@Arpad Toth I believe capacitive touch usually relies on capacitance to ground, and due to smaller surface area than a human a fly probably doesn't have enough coupling to ground.
I just tested my laptop touchpad by sliding a small metal piece around. When I pushed it with a plastic stick nothing registered but when connected it to ground it registered. Obviously when I touched the metal it also worked.
@@countzero1136 NCR calls their point of sale system "RealPOS". rather unfortunate name, though the touchscreen i got on ebay was pretty good
Dave you forgot one other type of touch screen technology. IBM had touch screens back in the 90's that were strain gauge based. The CRT (Yes old school!) was mounted on strain gauges (Like in an electronic scale.) and when you touched the screen the pressure and position of the touch was measured. These only worked for a single touch but you could have software that also reacted to the pressure of the touch. ie touch lightly to select and harder for activation.
You did have to have the screen on a very rigid surface otherwise you could get false touch touches if someone walked by or slammed a door. These IBM screens connected through the PS/2 mouse port and had connection for the mouse if you wanted that as well as the touch capacity.
Ahhh memories!
Check the LGR youtube channel, I think he made a vid on one of those IBM ones.
@@LazerLord10 Thanks for that. Yes the IBM 8516 touchscreen was the one I was talking about. I used those quite a lot back in the day.
so the apple force touch thing is ibm technology?
@@marcoaurelio4903 Don't know if it was IBM developed or just licensed from another organisation.
The 3rd sensor is to prevent occlusion enabling multi-touch. Also helps with dust rejection
Minimum of 3 needed to triangulate position of touch!
@@Petertronic Only 2 needed to triangulate a single point as the sensors are in the corners. The second point of the intersecting radii would be offscreen so could be discarded. The third sensor would be helpful for multi touch where 1 finger may block 1 sensors view of another finger.
Edit: the sensors don't sense distance. They just sense if light was reflected in a given direction. They don't work on triangulation, they find the intersection of straight lines
@@oM477o this is correct also keep in mind that the sensors are basically looking at a mirror and with a little math you can use the 2nd off space reflection as a checksum of the location data, confirmation of first point location, line sensors used are 1024 pixels wide fyi on this screen looking at the schematics and datasheets. Only 964 pixels are used in software
@@Petertronic Yes, but the finger position itself is the 3rd position.
Thank you for doing this teardown. Really interesting technology. It's amazing that they can get so good touch with three small linear sensors like that!
Really common for POS systems, easy to clean, and you can use anything to activate them, gloved hands, pens, i've used a handheld scanner or even product :)
*Mashing screen with lettuce*
Manager: good job jimmy thats using your head.
I worked at SMART who holds the patents for all of the optical touch screens. We took over the NZ company who infringed on our patents and rolled them into the SMART corp. Now SMART has been taken over by Foxxconn. I haven't worked at SMART for about 8 years, but I'm sure that design hasn't changed much in that time. As you've said many times, most of my time was spent reducing the cost of goods in the manufacturing of these devices. The technology can acquire and track up to 75 objects, it is software limited to a much smaller number, usually either 2 or 4, but some products can track up to 20.
There are 2 configurations, 1 with a tx/rx in each corner, 1 with a tx/rx in the top corners. This Dell unit appears to be not of SMART design, and thus very likely in violation of SMART's patents.
The waveform has peaks and dips as the retro-reflective tape has different reflection coefficients at different angles, the big dip is the drop off of the signal at the opposite corner. Each corner is multiplexed and there would be no way to determine where the shadow is, if the screen was just flooded. Also we drive the LEDs so hard that we can't drive them continuously.
If you have any other question, I'll do my best to answer them. :-)
What was the effective touch resolution like? It looks like there’s pretty massive touch latency. Is it from filtering?
@@float32 The touch resolution has many dependencies, but at the end of the day it always came down to user interaction and testing. If the users liked the operation of the device then the resolution as deemed good enough. Most of the time it turned out to be about 5mm for touch using your finger and about 2mm for touch using a pointing device. The latency was done the same way, and for most of our large displays a 10ms latency was acceptable. The topic of filtering is complex and the algorithm internal filters were all auto adjusting and tuned themselves based on how all of the other parameters were set. We had 2 Ph.Ds who did the work on this, it was quite complex, and yet all of this ran on some very simple microprocessors (mostly ARM based).
Industrial automation engineer here: I've never encountered anything but resistive touch in industrial application. Optical would be waaay too easily disrupted by dust and other gunk that there is plenty to go around. Not many production facilities are even close to being clean and neat. They'd have to deep-clean such monitors hourly to keep them working =)
Great video Dave.
I have had across my workbench some industrial grade optical "touch" screens and they have a scanner type linear array around each edge, a TX and RX pair opposite each other.
A bit more electronics around the frame of the screen.
Luckily not on the bench for any touch fault, usually backlight powersupply failure.
Hilarious heatsink at 14:04
It doesn't even cover the whole chip. Like why bother?
It'll still help pull heat out of the chip. The die, where heat is produced, is probably in the center anyway.
Wanted to save on the number of distinct parts and use the same heat sink for both chips, I suppose.
@@smeezekitty Die would be at the center and it's probably a small enough die. So this still helps with heat.
Simple in principle, probably a bit tricky to get working properly (re. signal processing). Cool video!
I recall being 12 years old and seeing those giant 1.5meter vertical touchscreens in a Sport Check. What I was wondering is how it worked and I asked. But I only learned that corporate in Munich handles it. Back than I wasn't that much into the internet to do my own research. I do recall that it would notice your touch before you actually so touch if.
Seeing this now made me wonder if that's it.
Most likely. But overly sensitive capacitive touch can do that as well but at that screen size resistive and optical are about it.. another method is used in rear protection screens with an IR flood and a camera mounted near the projector looking for IR spots reflected back on the from fresnel lens. Some used edge lit IR but most just pushed ir from the main projector with 980nm filter notch over the top of The dlp chip in most the last generation screens let it by pass the dlp chip and out the screen.
8:07 Looks really futuristic without that back cover and bezel.
The third sensor is needed for the multitouch. If you put one finger on the screen, for the sensor, there is an invisible "shadow"-Area behind your finger. So if you put a second finger along the sensor line behind the first finger, the sensor will not see it. Therefore there is placed a third sensor.
These were used on the early Acer all in one PCs. I used to work in the returns department for a high street retailer and they often were returned faulty with erratic touchscreen. Always was dirty screen and sensors / reflectors etc. I think they only had two sensors if I remember correctly.
I have one from HP at work. Once i thought the touch was malfunctioning but it was just a small piece of paper that got stuck between the sensors at the bottom edge of the screen.
There's an arcade game called "dance rush" that uses a very similar principle, I think. Definitely good for detecting multiple feet in an x-y grid and not wearing out after everyone stomps on it!
Dave, I was going to mention this in the vid where you first showed it, but have a potentially useful use for it. Don't you have an O-scope that has external video out and mouse support for operation? You could use that while doing circuit work, allowing the screen to be further back on the bench, while allowing all of us to see it.
Cool idea, but I don't think the touch sensor enumerates as a mouse? Will try it!
He showed the screen sensing pinch operations. You need the third sensor to properly resolve two fingers.
had a HP pavilion touchsmart all in one, idk the model, purchased at harvey norman approx 2008-2010, came with windows vista
tore it apart a few years ago, screen was similar but the frame+touch stuff was a lot thinner, completely independent, not connected into the main lcd pcb, powered over USB (no usb plug, just special connector for motherboard)
bought a lcd driver on aliexpress, didnt look at the voltage jumpers, released some magic smoke from the screen, touch still works, display doesnt
There is one touch technology that is really tricky. It uses 3 or 4 pressure sensors (load cells). When the screen is touched the screen moves. The loads cells measure the individual weights and triangulate where the pressure is applied. Never really took off due to resolution and size limitation issues.
I'm excited for this one.
That's what she said.
Facinating stuff. Cheers, Dave. I saw the IBM IR version in the 80's, so I made one on a 19inch B/W TV for my Spectrum. The resolution was crap. 5 accross the bottom and 5 down the side. LOL.
Remember that “high resolution” back then was like 1024 x 768, and that the application for those old touch screens was simple button press detection.
We have come a far way since then.
Seems it was sold in Sweden: ”Apparaten skall anslutas till jordat uttag”.
The LED is on momentarily. for many reason.
1 The led cannot stay on as it will overheat. It's a very small package and is driven hard.
2 It is only open during the "shutter" phase of the camera
3 There is an ambient acquisition cycle which is subtracted in software.
The 2000s was a special time when it came to tech like this, it is a shame that some of it was really good and little of the 2010s matched the build quality. Converting these older panels to led backlights is a bit painful but some have done it to laptops like the T43P and T60/61 ect.
There are some resistive touchscreens that support Multitouch, I remember seeing an Android tablet with a resistive touchscreen reviewed by Ashens quite awhile ago
The signal is not (much) weaker due to distance. It is the drop off in the return signal due to the corner cubes of the retro-reflector being off axis. The retro-reflective tape is very special as most tapes would not even work at those angles. I can pretty much answer any questions on this device.
So, we have two 1D PIN diode sensor arrays multiplexed (clocked) at 100 kHz. The return IR beams are focused onto the diode arrays so that the screen is divided into a thousand or more angular sectors. The beginning and ending angles of the shadows are marked so that the center can be marked from each top corner. The intersection of these two lines is the indicated location.
I have a SAW touch panel at work, we're currently waiting for a replacement from Japan, since the touch panel failed (it basically moved ~10cm to the left, so we had to move the display area to allow the operators to use it somehow) it's very hard to get a replacement for an old Japanese-market-only screen
Most SMART (brand) Interactive displays and other brands used in education use IR for their touch screens. Most have the retro reflective coating around the inner bezel. I think it serves 2 purposes. One it allows the glass to be very thick and resilient against hard touches and dings and the second it's probably cheaper than manufacturing a large capacitive touch surface, or at least it was at one time.
14:00 That is a funky heatsink. Doesn't cover most of the package, so I guess the actual chip is rather small.
I saw some hobbyists make interactive tables out of old rear projection TVs. Just put them on their back and put a piece of glass or plexi on it. Then shine a bunch of IR light out the front. Put a camera or like a wiimote in the back near the camera so it can see the whole front panel. Anytime you stick your finger or anything on the glass, it will reflect enough IR light back at the camera to get a touch point
I have a couple old Point of sale monitors with this type of touch system sometimes called "IR Touch" getting drivers for these older systems is next to impossible.. even from large stil in business manufactures like IBM and Toshiba.. there knowlage bases have dumped the older information and downloads .. so no luck as of yet getting these working .
I once worked for a laser spectrometer company and they had me design a circuit to use one of this linear image sensors. I have and had no idea what they were going to do with it. I thought it odd at the time for a linear image sensor to even exist.
As far as I know, linear image sensors are used a lot on the industry in quality check of products, imagine visually checking every single rice grain from a few tons of rice, with a 2D system that's near impossible. Now, just pass the grains through a canal where only one passes by the time, and you can shoot them at epic speeds through basically a scanner - the time it takes to pass through the sensor basically makes the 2nd dimension needed. Bad grains are then blown with compressed air to a secondary reservoir for further processing.
Oh, also as you mention a laser spectrometer: well it really needs no 2nd dimension after all! Makes sense to use a line image sensor there.
(In case anyone reading this is unfamiliar with a spectrometer: it divides light into each frequency that composes it through diffraction, like a rainbow basically. Where each light frequency/color will land on the scale is known through laws of diffraction, so all it needs is to hit the right pixel of the line, and it knows the frequency/color. You can check the emitted, transmitted or reflected light characteristics with this, and it helps to know what material you're working with).
I've seen a whiteboard scale system like this. It had a special diagnosis program that let you view the raw camera feed. I wonder if there is a public one for this device too?
I can remember testing the systems for the touch screens for the stock market back in 1986 which BT did with infra red
An interesting topic Dave and a great dumpster find your neibours must have quick turnover in their electronics.Just a query though, how did they cope with cross interference from the three emitters or do they work at different frequencies?
That's a neat way of using quite cheap sensors to make a large touch surface. All the voodoo magic is in the software that processes those three waveforms.
Interesting concept, and seems to work extremely well. I've never seen this sort of implementation of optical touch before, but several years back there were several homebrew concepts floating around the internet of optical touch systems using a couple of webcams modded for IR sensitivity and used in conjunction with a rear projection screen. The idea was that one or more webcams were pointed at the back of the screen and when you put a finger (or several - it worked for multitouch) on the front of the screen, the webcam imaged a blob at that point, reflected from an array of IR LEDs mounted at the back (in one design they used a Wii sensor bar (which is a multi-LED IR emitter and not actually a sensor at all) as the IR emitter. It was a simple system that relied heavily on custom software for operation, and while it did work, the resolution was fairly poor and rear projection is only really suitable for large-ish installations. Nice idea though.
I did a few experiments of my own back in the late 90s with optical XY sensing (the plan was to try to build a graphics tablet using IR LEDs and receivers. My basic arrangement was to have an IR phototransistor in each corner, while the IR emitter LED was in the pen. That way I could power the pen from a battery and avoid trailing cables. The LED itself was pulsed at around 10KHz and the receivers capacitively coupled in order to avoid being swamped by ambient light. My prototype only had a single button, and when pressed, it increased the pulse rate to 20KHz which was detected by the receiving hardware and used to emulate the left mouse button. The whole system interfaced to the PC as a PS/2 mouse and as such didn't require any driver software.
The outputs of the four IR detectors were integrated and matrixed to provide an analogue voltage proportional to the X and Y positions, and then converted (using a bunch of 4000-series CMOS logic ICs) into a digital signal compatible with a PC mouse.
While the prototype did work, it was quite finicky and the pointer tended to jump around way too much for it to be useful as anything other than a novelty item. Positional accuracy was fairly poor but the worst problem was that I was never able to get rid of the non-linearity of the receiver circuitry - No matter what tweaks and mods I made to the project over a period of around 17 months, I was never able to get an even response, so the movement was all squashed up towards one end of each axis and very insensitive or sometimes unresponsive at the other end, so eventually I abandoned the project and moved on to other things, but it was definitely an interesting concept to mess around with, and I'm sure it could have been made to work better given more time and effort, but by then, better and cheaper options were already on the market.
It's very nice to see that a commercial manufacturer has managed to get a broadly similar concept to work though - I did have a Packard Bell All-In-One PC that came into my shop for repair a few years back that had a 20" touchscreen, but that one was resistive iirc
of course one of the reasons dave came back to the old lab was to have access to the dumpster room again. Since he was not there anymore the building manager wouldn't allow him to enter that room. lol
Err, no, I've always had access to the dumpster room. I *own* part of the dumpster room.
@@EEVblog you've gotta admit that the scenario i described was very plausible. i would go back as well if it happened to me. ;)
if there is 3 sensors must work on triangulation of where your finger is.Thanks for the video. Like the tear down. Learn something new every day.
Wow that is a cool way to register touch!
I've done field upgrades to a bunch of those self checkout kiosks. Only one set I had to stop was a store still using CRTs with a touch screen box. Past my pay grade at the time for that. But I got to plan my route and visited NASA of Florida at the end of my month of robot maintenance.
Reminds me of one of my HP logic analysers that had a infra red touchscreen. Sorry i forget the model number just that it’s revision C with the hard drive.
My first thought on the strange waveform was some dirt on the reflectors/sensor
They use this tech at my uni in the massive screens in the classrooms instead of chalkboards. Capacitive touch would be a bit too expensive i believe. Anyway, bloody annoying during a presentation when you accidentally get too close.
Another great video. This is a quite interesting device and you give a much more interesting analysis. Thank you, Dave! If you look closely at 7:14 - a vertical light stripe occurs on the right hand edge of the frame. I guess that’s the retroreflector reflecting part of the light of the camera's IR distance sensor right back into the camera.
I have a 70 inch version of this, It's a commbox which i purchased from Grays online for $500. Best thing ever. It also has a toughened glass screen so it can take a heap of PlayStation and Xbox remotes thrown at it all day.
I just had a look and found that mine only has two of the sensors embedded in the top frame, It's still multi touch though and accuracy isn't too bad for what it is.
Don't know if you forgot or didn't know, but optical infrared touchscreens are actually quite common. Most of the greyscale Kindles use optical touchscreens and those are are/were very common. Sure, I guess they're relatively rare but I interpreted your words to imply that it's obscure, which it very much is not. Honestly, I'm a bit disappointed that you didn't turn the lights off and let us see if the infrared emitters glow on camera. Thanks very much for the teardown!
you can use gestures with resistive too even the old pocket pc have it ;)
How many Fingers does this ‚truly‘ support? If i remember correctly, beginning with the second finger, there was a trick: the screen would only detect the second finger, position of the first finger was fixed. This was improved later but did require more sensors.
Back in the 80's my gradeschool computer lab had an IR touch-screen adapter that stuck to the front of an apple 2e monitor with 2-sided tape.
The HP L2105M is also Optical touch. I have picked them up for $50-70 on ebay in the past. They work great but i think they are only 3point tracking.
One of our customers has a custom touch-enabled video wall spanning some ~25' (~7.5m) diagonally. I _think_ it works on some kind of interferometry. Essentially, it seems to have IR LEDs scanning around the perimeter, with what appear to be IR photo diodes in the corners. Connects to a controller that translates the contraption to a standard USB HID device, supplying Windows the 10-point multi-touch. The wall is entirely modular -- scanning LED bars and multiple thin-bezel LCDs make up the bulk of it. The customer's none too keen to have me take it apart, of course, and the manufacturer is mum on details (beyond that it uses IR), so that's as far as I've been able to figure out. 😁
Well, you need at least 3 corners/sensors to be able to "see" from every angle on the XY plane. And 4 sensors would be overkill.
With only 2 sensors, if you're finger is in front of one of the sensors, there won't be enough resolution data to pinpoint the exact location, with 3 sensors, if your finger is too close to - or blocking- one of the sensors, the data from the other two sensors are used for better resolution.
Also, if you only have two sensors in the bottom corners or opposite each other, it will be harder to figure out multi-touch gestures, because with only two sensors there will always be a blind area where touches would not register.
I think there's a 5th type of screen that's strain-gauge based that some early PDAs used. But that might just be my internalized explanation for why resistive screens required calibration.
Feels to me like that would be an interesting way of adding either pressure sensitivity or point size detection to resistive screens. As far as I know they're a bit more simple even: just a voltage divider turning on at X or Y and that's it.
To be honest I find it so fascinating how brutally simple they are, it's really impressive in it's simplicity.
Small touch screen devices such as standalone GPS (Tom Tom) and some ebook readers use optical touch
The new Suzuki Jimny has an infrared touch screen for the infotainment. Makes sense for ruggedness.
There is a radar method as well.
I had never heard of optical touch screens other than the 70s/80s 16x16 or whatever LED/sensor pairs!
Great video, i prefere these kinda measuring-teardown videos. Use an infrared camera, maybe you see the signal. I think they need 3 leds because you can use 2 vingers or it has to do with the size of the screen
That's going to come in really handy for looking up schematics.
I wonder what it would look like if you took your reference snapshot and subtracted it from the signal? Sort of like the tare button on a scale. Maybe it does that in software already?
This looks to be similar to SMART's interactive Displays. Camera and IR modules in the corners... though probably doesn't have the same level of resolution. Edit: Digital Vision Touch is what SMART calls it.
I have for the longest time been wondering.
When will a screen manufacturer just include a bunch of exposed diodes among the pixels. Since a diode is a photo sensor.
Just black out the frame for a literal moment, sample all the didoes into a sample and hold circuit, and read them out...
One would get a literal light map of where stuff is currently blocking the screen.
Though, I can see that this would require yet one more sample and hold circuit for each pixel, and likely a set of buses for reading it out, not to mention ADCs thrown into the line/column drivers.... Potentially not the slightest bit cost effective in comparison to other touch technologies. But I haven't seen anyone even talk about it before.
And if the photodiodes have a diffuser before them, then one could just compare the value to the average of the whole panel, and if it is bellow that average, it is shaded, making ADCs redundant. This might seem even more complicated, but since we can output the sampled value onto a signal plane via a high valued resistor. Then the voltage of the plane would be the average of all the voltages feed to it, and from there we can read back the value compare it to the sampled value and simply output that state.
But I can see noise as a potential issue here... Especially if no pixel on the panel is currently being prodded at, so including an offset would be needed. But that offset can just be a resistor between our signal plane and our ground, ensuring that the "average" is always slightly bellow the actual average, ensuring that unshaded pixels aren't seen as shaded. But this creates a problem when the whole panel is shaded, but that is a weird use case for a touch screen to be fair.
Now, since I still haven't seen anyone even mention using a photodiode array as part of the screen itself for use as a touch screen, then I guess by virtue of this explanation now being in the UA-cam comment field would practically put the idea into public domain, making it non patentable, and even less interesting for touch screen manufacturers as a result...
Interesting approach of (as far as I understood your idea) embedding the sensors among the pixels, but wouldn't that require as well a constant light source? Can't really count on surroundings or image shown. I can imagine an IR LED (or for an LCD let it through from the backlight itself, add it to the backlight of course) at a specific frequency, so no tracking background IR, that would actually be pretty interesting. Tracks anything, as many points as you want, and no added bezel to have to dust off. BUT, can reduce brightness from reduction of the lit pixel area, which in other hand might be compensated by the lack of an extra layer of transparent semiconductors.
@@Kalvinjj My idea were to use diffusers on top of the diode, this would largely average out the light in front of the display.
Using the display itself as a light source and watching for reflections is also an option. All though, here it could get debatable if one can easily tell the difference between the displays own light and surrounding ambient light shining onto the pixels. Not to mention that we also need to sense if the pixel gets brighter or darker, instead of just darker. (unless our integrated light is really powerful to outcompete any external light sources. But this is questionable if it is practical or energy efficient.)
Now, having poked about at the sensing solution using the idea I postulated in the prior post, where we compare each value to an average, such solution can use as little as 5 transistors per pixel. (2 transistors for a comparator, 1 for reseting a capacitor, 1 for buffering the accumulated voltage on the capacitor and 1 for handling our output scanning.) This is a fairly trivial design and would only need 3 power plains. (1 plain for actual power, 1 for the average signal, and 1 for feeding the photodiodes, so that we can account for varying degrees of ambient light.
But the main advantage with this sensor array is that it just outputs a bitmap of what pixels are currently shaded, no fancy mathematics or position calibration required, if a sensor says it is shaded, there is something on top of that specific pixel. (or the sensor is broken...)
U turned it on Dave!!
Dell stand-alone computers use the same touch screens, I knew they were using infrared (have inspected with my phone camera before but I didn't dare to try a tare-down. I would assume that the third sensor gives some redundancy and tolerance against dust.
Thank you so much for sharing!
i'm probably missing something here. But how does it differentiate a finger touching the screen from a finger just close to it?
Was the non-existant sensor on the top or the bottom?
You can buy touch frames like this www.amazon.com/infrared-without-interface-free-drive-monitor/dp/B078X8R9Z3 and double-side-tape them to a TV to make them touch capable.
I already had the chance to mount these at a client's place. Remember to avoid TV with thin bezels. They don't have enough room for the frame to hold on.
Actually you can use two fingers on resistive and it also has a "Z" axis. How do I know. I have the chips with the program and I worked on resistive way before other touchscreens were out.
bloody hell open it already!
You missed another touch screen technology, although I think it's pretty much dead: mechanical. They work(ed?) by measuring the small amount of torque resulting from prodding the screen. We had one at work years ago, or rather, we had a stand that could be used to adapt any CRT monitor -- it took some calibration, and you had to press quite hard resulting in gorilla arm, and I can find no reference to the technology anywhere, but I *know* it existed!
I didn't even know this kind of touch screen existed until I (unknowingly) ordered one a few weeks ago.
For just €50 more would have gotten the real deal. Should have returned it...
7:22 On the right side of the back sticker, there is Swedish, Norwegian and Finish warning about grounded plug. what is that doing on a tv from Australia?
these integrated powersupplies are mostly certified for many countrys/regions at once.
You can also see the CE Mark (for EU) the "pCT" (Russia), the CCC (China) the "Tick" (Australia) etc.
the international Eletrical Safety norm IEC60950-1 has only small deviations for many countrys and its way easier to "take them all" in one testing and you are ready for most of the World selling your product.
Also many Authorites demands that you have to use a registered typ-plate in the testing so its eaysier to make a "one fits all demands" plate in one go.
Resistive multi-touch screens do actually exist, they're just not very common.
3 sensors would allow for more touch points.. easier to triangulate the position of multiple points with 3 than 2...with 2, points can be hidden behind other fingers etc
For two fingers that's no the case, two sensors is enough. But yes, more accuracy on more touch points.
Interesting background picture. A cardiac pacemaker?
Wanna drink a beer - with that engineer YO!
They are not rare, All the SmartBoards that Smart Technologies makes use's infrared cameras. They invented using infrared cameras for touch screens. I know because I use to work in there call center here in Canada providing technical support.
I have a medical-grade all-in-one with a third-gen mobile i7 in it, but is 1280x1024 with this type of touch panel. I can't get Win10 compatible drivers and the only ones that exist which I can find are for 32-bit Windows 7 and up. You're not kidding about them being rare, even the drivers are rare, if it's not a well known brand.
Cool stuff!
Dave, you weird guy. I was just researching IR touch screens in the pursuit of a DIY touch layer.
When electrical engineers graduate here in Australia, are we allowed to perform typical electrical work or do we need to do an apprenticeship to get the badge of operation?
Nope, you need an electrician license. The laws are very strict. You could have a PhD in EE and you still are not legally allowed to change a power point.
@@EEVblog That's honestly very annoying for EE but yeah I get the safety side of things.
I would think they would multiplex the sensors, at least the two oposing ones.
Well, more cameras give more angles...
I suspect you could get dead spots behind other fingers if you try to implement more than 2 finger multitouch
More than two fingers, yes it gets less reliable. For two fingers two sensors is enough.
My iphone camera does not see IR, but the one reverse on that looks at your face does.
I wish I knew what part that was
First thing that comes to mind, when I hear IR touchscreen are whiteboards in schools (the use projectors for display).
ohh we had that!!! Complete bullshit. even the whiteboard surface is bad!
@@marcoaurelio4903 When I think about it I've used one that had sensor unit ~1 foot in length attached on one side of a normal whiteboard and required a battery powered pen/stylus. All the other ones were more of a hard projector screen and not to be written on.
It maybe the touch part of it is powered by USB so that's why nothing worked until it was connected to a USB port.
I hope next video content you make Or DIY infrared touch screen frame from scrap printer Scanner 🤗 im waiting thank you sir
Retroreflectors only work in 90 degree FOV, if you go beyond this 45 degree off the middle axis it wont reflect light back to you obviously. This is why they needed the third one sensor I believe. The light wont reflect from the farther corner along the longer side and this is probably seen as a drop in attenuation on the oscilloscope.
This is my crude schematic illustration of this imgur.com/3kUGDtr
In other words. All the sensors see the opposite shorter sides but the two on the bottom only see part of the longer opposite side because on the farther side light touching the reflector strip on the angle which is too acute and reflector strip don't reflect light back to the sensor.
Yes exactly. After a drop in intensity on oscilloscope scanline along the longer side there is a sudden raise when the light starts reflecting from the shorter side passing the corner.
IMO with just 2 censors it would work basically the same just a bit less responsive
Thanks for sharing. 😉👌🏼
Should try and find a acoustic touchscreen to tear down
Can this be turned into a diy project???