How2? Touch Sensitive Panels ala 'Star Trek' - creative solutions
CounterRotatingProps
Posts: 1,132
Picture the control panels of the later Star Trek series...
I'd like to make something that looks similar, without using a 'touch screen' monitor.
1. Take a 1/4 inch Lexan/plexiglass sheet - WxH are arbitrary
2. Mask off the underside with the design that would show through
3. Spray the back/underside of it flat or gloss black.
4. Remove mask.
5. Mask again where needed...
·· 6. Spray with transparent color...
·· 7. Repeat step 5-6 as needed to get all colors.
8. Backlight with LED assembly.
The part I don't understand - or if this is even·possible:
A. Can CapSens material(*) be made translucent/transparent?
B.·Can it be put underneath the plexiglas and still·work through·such a thick piece of material?
*) What would the·CapSense sensor material·be made of?
Thanks for your insights and suggestions!
- Howard
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Post Edited (CounterRotatingProps) : 10/28/2009 2:23:24 PM GMT
I'd like to make something that looks similar, without using a 'touch screen' monitor.
1. Take a 1/4 inch Lexan/plexiglass sheet - WxH are arbitrary
2. Mask off the underside with the design that would show through
3. Spray the back/underside of it flat or gloss black.
4. Remove mask.
5. Mask again where needed...
·· 6. Spray with transparent color...
·· 7. Repeat step 5-6 as needed to get all colors.
8. Backlight with LED assembly.
The part I don't understand - or if this is even·possible:
A. Can CapSens material(*) be made translucent/transparent?
B.·Can it be put underneath the plexiglas and still·work through·such a thick piece of material?
*) What would the·CapSense sensor material·be made of?
Thanks for your insights and suggestions!
- Howard
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Post Edited (CounterRotatingProps) : 10/28/2009 2:23:24 PM GMT
Comments
LCARS – Library Computer Access & Retrieval System
I tried to use Flash once to make a website built around this type of interface. I failed…probably just as well. Anyway, touch sensors such as those that are used in iPods are very common now and there are several IC manufacturers that make chips that handle multiple channels and arrays to implement such a system. Many have sensitivity adjustments and filters for situations such as you describe (Freescale MPR121).
I still think a touch-screen could realize this better, but I am not clear on what you’re planning so that is a matter of perspective. You can check into that IC or ones made by Quantum Research Group (we used to carry the QT113). I hope this helps. Take care.
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Chris Savage
Parallax Engineering
50 72 6F 6A 65 63 74 20 53 69 74 65
·
Yes, there are quite a few companies making such chips. I appreciate the specific suggestions.
I'd like to be able to make odd-sized and larger panels. So, touch screens wouldn't work.
> Many have sensitivity adjustments and filters for situations such as you describe (Freescale MPR121).
I'll dig in the datasheets and see if there is a penetration limit.
The "electrodes" seem to be a simple conductive material ... I wonder if there's a clear, electrically conductive film, plastic or foil that would work?
- H
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This company might be of interest, their SAW (Surface Acoustic Wave) Panels might be of interest.
www.densitron.com/Displays/Content.aspx?id=2190
The technology of SAW sensing is such that you could apply this to just about any surface.
www.touchuserinterface.com/2009/08/acoustic-touch-sensing.html
...And yes, the Propeller could probably do something very much like this using acoustics, but to my knowledge I haven't seen anyone apply this.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
You guys are the best!
> the Propeller could probably do something like this ...
and you seem to be mind readers too [noparse]:)[/noparse])
The SAW Stuff is very interesting!
On the touch sense side, I came across this a while back (not sure if it can do the job, but it's cheap) :
PSoC3 "FirstTouch" starter kit
http://www.cypress.com/?rID=38235
l
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you can make touch sensitive panel through as much as 1/2" glass though the thiner the easier it is to read.
the bad part is you need to make a pcb the size of your screen for the cap sens traces. for back lighting though you can use reverse mount surface mount leds and drill wholes through the pcb. you can also get clear pcbs made but i have not found a suplier yet and the coper will still be visible.
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Links:
8 Pad touch sensor controller
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MPR084
8 position rotary controller
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MPR083
3 axis acceleration sensor
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MMA7260QT
Badgeboard
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=JMBADGE
Schematic for BadgeBoard - also shows how the sensor chips are interfaced.
http://www.freescale.com/files/JMBADGESCHC.pdf?fpsp=1
A) Capsense pads must be copper (well conductive metal...) so the translucent question is a no.
I have the CY3270 First Touch kit for the Cypress PSoC. It has a Capsense Slider on it and it is really easy to see how to utilize capsense pads using that kit. It is $33 at Digikey. (was $20 when I got it a couple years ago)
Cypress PSoC chips can do CapSense through various thicknesses of material. I know of a couple designs that use a dime sized pad and work excellent through 1/4" acrylic. I have also seen various designs using Qtouch parts. One consists of pads about 2"x1.5" and it mates behind a 0.150" thick piece of polycarbonate. The Qtouch parts are a lot easier to use because once you determine the variables (pad sizes, part values) you just build it and it will more than likely work. With the PSoC parts, you have to program the specifics in addition to determining values and pad sizes. The PSoC Designer IDE is reasonably easy to use if you have previous C experience to understand what the visual interface is creating. The difference with the PSoC however, is that you can throw down a circuit and modify your coding to make it work even if the circuit is less than ideal. This may be the best choice because you could use discrete wiring to foil pads on your display and use the PSoC feedback programs to see how the circuits react to fine tune your capsense settings. This would require a lot of trial and error with wiring design and programming though.
Some things to look at:
Capacitance Sensing - Layout Guidelines for PSoC CapSense - AN2292
www.cypress.com/?rID=2887
Quick Layout guidelines
www.cypress.com/?rID=34564
CapSense™ Best Practices - AN2394
www.cypress.com/?rID=2883
Attached is a document from QTouch about secrets for a successful design. I have one of the older QT240 demo boards that I bought for a project because it was easier to spend $19 on a demo board then it was to design/build my own.
You can also use springs to have a larger gap between the PCB and the overlay material. The second PDF attached has details on how that is done.
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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010
There are several ways that these things work, one being charge transfer. (In Quantum parts such as the QT113, the QT stands for charge=Q Transfer). The plate is first charged up to a certain voltage, say 3.3 volts by connecting it to (say) a Prop pin set high. The pin is then set as an input, and then an analog switch is closed that connects the plate to another capacitor that is connected to a comparator input, which might be a Prop pin. The capacitance of the plate is small, so with one cycle of charge transfer, the voltage at the comparator input does not rise by much, so it takes many cycles of charge and transfer to reach the comparator trip point, but it takes many fewer when someone is touching the plate. I'm just saying you could experiment on your own with simple components without getting into a fancy development technology. The simple single plate configuration takes 3 prop pins and an analog switch or fet. That is not to say that there are not subtleties to deal with. Fancy sequencing of analog switches can deal with differential capacitance and multiple plates. Narrow charge transfer pulses can deal with water films and contamination. Digital filters can deal with gradual drift. etc., what fun! I have made these using the SX, which is good for fast switching sequences.
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Tracy Allen
www.emesystems.com
thanks much for the detailed guidance - I really appreciate that. Looks like this is not so simple after all !
Very interesting that there isn't a clear/translucent conductor material of some kind - or is there some high-tech stuff that costs too much? I've been mucking around on the net looking, but no luck. This surprises me actually. One idea: I wonder how much aluminum or brass/bronze powder (c.a. 500 mesh) would be needed in an acrylic or epoxy pour to get the balance between conductivity and clarity ... probably would end up looking smoky ... interesting problem.
- H
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I think a low-tech bag or sandwich of clear water would work fine. Especially if you increase the conductivity a little bit with something like KOH. The electrical contact for that area would need to be only on the edge. There might also be a suitable gel.
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Tracy Allen
www.emesystems.com
Please do post a supplier or two when you get a second ... I hunted for a while but didn't come up with anything realistic.
Interesting ... while searching, thin film solar cell's came up (TCO's = transparent conductive oxide).
@Tracy - do you mean one of those anti-static bag's that our e-goodies come in?
DOH ! I didn't think about the fact that they would *have to be* conductive to drain the static... one man's trash is another's treasure, eh? [noparse]:)[/noparse])
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I was actually thinking of the water being the conductor, or even water that has been gelled stiff with something like polyacrylamide. It could even have food coloring added to make the colors. I just don't know how you would hold that on the bottom of the table. It would have to be some kind of sandwich, but the gelling could help.
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Tracy Allen
www.emesystems.com
if you use reverse mount leds on a pcb you only need a small hole for the light to transmit through. Or you could mount leds into the plexiglass from the sides like some LCD screens and let it reflect off your pcb and the surface of the plexiglass. will make a decent defused lighting.
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@Todd - that is a very reasonable price for such a large roll. No hurry, when you get a chance to dig out the info, that'll be great.
@Matt - thanks for clarifying the approach. Both ways (rev. LED & side mount) would work for certain parts of the display, but the bulk of it needs to be really clear. The side mount LEDs are nice for certain things.
I also have a fun trick using cheapo fiber optics... sort of obvious: just channel the light where you need it. Hot glue or epoxy the firbers along the masked out (dark) areas, terminate them under or even drill in at the desired display area. The other ends come together in the LED matrix, which can be tightly spaced. I use a second perf board laid on the top of the LED matrix... the fibers poke into and slightly through the holes, aimed at its specific LED. (Oh, I should just make a .jpg... would be easier to see.)
There are several reasons why I'd like fully clear - the main one is being able to put a cheapo LCD just underneath the main panel (flush), but have the panel 'touchable' ... a cheap(?) way to make a touchscreen out of one that isn't. But more, integrated into a larger touchable panel.
Thanks again for your suggestions, guys - please keep them coming !
- Howard
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I am pretty sure this was the company. They sell the ITO film in a roll or maybe cut lengths.
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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5
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Computers are microcontrolled.
Robots are microcontrolled.
I am microcontrolled.
But you·can·call me micro.
Want to·experiment with the SX or just put together a cool project?
SX Spinning light display·
Want cheap wholesale electronic parts?
Transistor parts wholesale
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=BER281-ND
21" touch screen film for $94
that and a TSC2003 will give you a large transparent touchable surface.
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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5
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If I understand the cover and chip at quick glance, it looks like resistive /pressure sensitive.
I need the 'sensor' material to be underneath then plexiglass/or normal glass.
still, thanks for the suggestion.
- H
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Capacitance sensors can go behind but trying to build capacitive sensors out of some of the suggested clear materials would probably be very difficult.
another method i have seen used is an array of infared transmitters on bottom and left side and infared receivers on top and right side. where the signal breaks gives you finger location.
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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5
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The metal layer in the resistive touch screen must be very thin to be semitransparent with high and stable resistivity. Is it aluminum, or some other metal? I tried measuring on the surface of a static shielding bag, but either my ohmmeter does not have a high enough scale, or the metal is not actually on the surface.
It is interesting how conductive properties are associated with opacity, the imaginary part of the light scattering parameter for metals or carbon. Ionic conductivity requires some kind of liquid or gel medium.
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Tracy Allen
www.emesystems.com
> or the metal is not actually on the surface.
I had to chuckle reading this, Tracy, having tried *exactly* the same thing. Zilch! [noparse]:)[/noparse])
Seem's like these bags might still work for the capacitive version --- assuming we can *find* the metal to hook onto.
> It is interesting how conductive properties are associated with opacity, the imaginary part of the light scattering parameter for metals or carbon.
Guess that's why we can't have windows made out of aluminum?
The SAW (surface acoustic wave) method is looking more and more attractive. --- or maybe a combination of IR and SAW... and I thought this would be simple [noparse]:)[/noparse]
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http://parts.digikey.co.uk/1/1/449435-board-eval-qt60248-as-qmatrix-e6248.html
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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5
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I recall reading about clear aluminium somewhere...
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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5
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the concept is that LEDS have a falloff rate due to the photo electric effect, so I propose that a touch panel be made using el-sheets and the propeller.
The capacitive nature of the el-sheet, el-tape or el-strips might just allow us to use them as both light emission and capacitive detection of the finger.
I don't have any el-sheets but I have el-wire, but don't have a scope. The only way i can test it, is by programming a prop.
I would just rather order some el-sheet and test that.
electroluminescence-inc.com/ELsheets.htm
ahh yesthats right...,although with todays femtosecond lasers, transparent aluminium is not so "star trek"
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TERMS OF USE: MIT License
"Permission is hereby granted, free of charge, to any pers...........................
..............................OMITTED FOR FORUM...............................................
.................. OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. "
The dsp/fpga king is dead, long live the prop.
Post Edited (Clock Loop) : 10/26/2009 3:57:40 AM GMT
Here is el-FLATLIGHT
www.e-lite.com/flatlite.htm
If this works, one could make a LCARS panel, using only this el material, a propeller, and a speaker. (plus High Voltage interface circuit)
The problem is with casting shadows over buttons that you didn't mean to push. (if you try led method)
If the el material can be used like a touch capacitor, (it does run at 100+ volts ac around 1khz) (almost no current though)
With that kind of voltage running under a thin piece of plastic, is it possible to detect a persons finger using the capacitive nature of the el sheets?
Because its not just a LED like material, but its also a huge flat sheet of sudeo metal (aka semiconductor)
Wish I had some spare cash to test this.
Why yes, yes I would like a LCARS glowing touch panel, propeller powered, that even has the beep when buttons are pressed. And affordable also.
Com it up to your pc, and program keyboard shortcuts.
Bye bye keyboard.
HELLO LCARS.
I think this method meets all required conditions to create what you guys want.
This idea was inspired by my own experience with EL-wire and using LEDS as touch sensors.
I realized that the el-materials are ideal for this application.
SHAPE LIMITATIONS OF FLATLIGHT.
www.e-lite.com/PDFs/FB_SHAPECONSIDERATIONS_ELITE_E1.pdf
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TERMS OF USE: MIT License
"Permission is hereby granted, free of charge, to any pers...........................
..............................OMITTED FOR FORUM...............................................
.................. OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. "
The dsp/fpga king is dead, long live the prop.
Post Edited (Clock Loop) : 10/26/2009 5:36:17 AM GMT