Touch-screen technology?
Archiver
Posts: 46,084
Anyone know if there's a cheap way to implement a touch screen? I'd
like to be able to track the location of a finger/stylus/whatever, in
a 5x5 grid on an lcd screen. I'd like to do this as inexpensively as
possible, even if the solution is not pretty.
Thanks,
-Chilton
like to be able to track the location of a finger/stylus/whatever, in
a 5x5 grid on an lcd screen. I'd like to do this as inexpensively as
possible, even if the solution is not pretty.
Thanks,
-Chilton
Comments
face of the display and watch for one or more beams to be interrupted.
Original Message
> Anyone know if there's a cheap way to implement a touch screen? I'd
> like to be able to track the location of a finger/stylus/whatever, in
> a 5x5 grid on an lcd screen. I'd like to do this as inexpensively as
> possible, even if the solution is not pretty.
the
> face of the display and watch for one or more beams to be interrupted.
>
This is an option I had considered, so I may do this, now that someone
else has officially thought it was a good idea [noparse]:)[/noparse]
Another option would be to use magnetic reed switches underneath the
lcd screen. Would that affect an lcd screen? Would it affect wireless
communication? Would it affect the performance of the Basic Stamp?
What if I transmit two high frequency RF fields across the front of
the screen and check for intersecting distortion patterns?
-Chilton
1) Capacitive sensors in the screen (expensive).
2) Light beams.
3) Sound waves.
Someone has a patent on #3 and I've never actually seen it done. The idea is
they send a ultrasonic chirp down one edge of the screen. Baffles direct
some of it back to a sensor. When your finger gets in the way, it shows up
as a missing return pulse. Of course that only gives you one axis. But you
can double it and only have 2 emitters and two sensors:
Detect
\
\
\
| |
| |
| X |
| | |
| | |
Emit
/
/
/
The classic way is to use an array of IR emitters and sensors. The old HP150
did it that way. You just criss cross the screen with light beams and watch
for sensors to go dark. Cheap enough but there are a few catches. Resolution
is poor for one thing. The other is to avoid ambient light problems you need
to put the sensors in a hole that points right at the emitter. The HP150 had
a bezel that had little holes in it. But, the little holes would fill up
with crud and become unusable. We'd snap the bezels off, take them in the
lab, and shoot them with air from the little shop air vents we had with the
anti static deionizer head. Then they'd be good as new for a month or so.
Have you considered a light pen? The idea there is to monitor a photo
detector for a light change. We used to make these for the RCA 1802 ELF by
hooking an CdS cell up and then "scanning" the (pitiful) graphics display.
Say you had 4 objects on the screen, a circle, a rectangle, a square, and a
triangle. When you push a button, the program would dim each figure and
watch to see if the pen's sensor drops. If it does that's the one you are
over. You do the scan quickly so it is hard to notice. If you are really
clever, the push button is built into the pen so when press it on the screen
it triggers a scan. If you use a phototransistor or diode and a lens you can
get pretty good resolution.
Real controlers use a raster scan to do this (the original PC could take a
light pen). I always though light pens would catch on -- better than a mouse
if you ask me (except for the difficulty with high resolution). Oh well,
I've always been anti-mouse.
Regards,
Al Williams
AWC
* 8 channels of PWM: http://www.al-williams.com/awce/pak5.htm
>
Original Message
> From: chilton@t... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=XPQ3V-xPXAF_MNGrcUVwbn9DCjSjdFearj2zy6pIDiqsLKuzio0yrYp4etiSiVxYNHQ3QMWclVd2]chilton@t...[/url
> Sent: Friday, March 02, 2001 1:00 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Touch-screen technology?
>
>
> Anyone know if there's a cheap way to implement a touch screen? I'd
> like to be able to track the location of a finger/stylus/whatever, in
> a 5x5 grid on an lcd screen. I'd like to do this as inexpensively as
> possible, even if the solution is not pretty.
>
> Thanks,
> -Chilton
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
stylus(pen)presence and position with very high accuracy from a 1/2"
apart.(I dont know if this will work with a LCD between)This seems a
good distance. The drawback is the need of a special driver running in
the PC environment and the PC serial port connection.
ACJacques
chilton@t... wrote:
>
> Anyone know if there's a cheap way to implement a touch screen? I'd
> like to be able to track the location of a finger/stylus/whatever, in
> a 5x5 grid on an lcd screen. I'd like to do this as inexpensively as
> possible, even if the solution is not pretty.
>
> Thanks,
> -Chilton
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
display you like. These have two layers separated by nearly invisible
silicone dots. With a little hardware you can make any size matrix you like,
and poll it like a switch pad. When last I looked, it didn't seem too
difficult. Post back a message if this sounds like it might be what you're
looking for - and I'll dig up a vendor name for you...
Chris
>
Original Message
> From: chilton@t... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=g758I1tN0kefDD98r4hqTgc8CnyWDn5Be9jgQWqfDEJs0Pd-zPGE0cl4UAfk5DNAGGV3ILFeR9c]chilton@t...[/url
> Sent: Friday, March 02, 2001 1:00 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Touch-screen technology?
>
>
> Anyone know if there's a cheap way to implement a touch screen? I'd
> like to be able to track the location of a finger/stylus/whatever, in
> a 5x5 grid on an lcd screen. I'd like to do this as inexpensively as
> possible, even if the solution is not pretty.
>
> Thanks,
> -Chilton
>
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
whatever
> display you like. These have two layers separated by nearly invisible
> silicone dots. With a little hardware you can make any size matrix
you like,
> and poll it like a switch pad. When last I looked, it didn't seem too
> difficult. Post back a message if this sounds like it might be what
you're
> looking for - and I'll dig up a vendor name for you...
>
Please do!
-Chilton
product.
Thanks
Nick
Original Message
From: <chilton@t...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, March 03, 2001 5:00 PM
Subject: RE: [noparse][[/noparse]basicstamps] Touch-screen technology?
> > There are digital touch panels that are made to be overlayed on
> whatever
> > display you like. These have two layers separated by nearly invisible
> > silicone dots. With a little hardware you can make any size matrix
> you like,
> > and poll it like a switch pad. When last I looked, it didn't seem too
> > difficult. Post back a message if this sounds like it might be what
> you're
> > looking for - and I'll dig up a vendor name for you...
> >
> Please do!
>
> -Chilton
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>