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> Materials That Trigger Capacitive Touch Screen, (iPad or iPhone)
Wizfinger
  Posted: May 07, 2011 09:40 pm
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Hi, I've been Googling for capacitive materials to operate touch screens.

I am trying to find out if there are any materials out there that can be used on the Apple iPhone or iPad, without conducting the human finger's bioelectricity.

I can find lots of capacitive styluses out there, but they all seem to work by holding them with your hands. The application I am looking for, however, is controlling an iPad without human touch involved.

For instance, a material that will be detected by the iPad screen when you lay the iPad flat on the table and simply place a small circular piece of said material on the screen and then let go of it.

Or, as a second example, a small spherical object (like a marble) that rolls over the iPad and triggers the capacitive screen even when no human is touching it.

Perhaps there are any ideas about this?

Or would it simply be impossible because there is always some electricity needed in the object that is touching the screen? Would it, in that case, be possible to build a small battery-powered device that triggers the screen?

Hope you can help,
Thanks!
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tekwiz
Posted: May 08, 2011 05:57 pm
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The first step is to determine the exact type of touch screen used, as there are several different methods.
It should be possible to activate any of them without a human touch.


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MacFromOK
Posted: May 08, 2011 11:14 pm
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QUOTE (tekwiz @ May 08, 2011 11:57 am)
It should be possible to activate any of them without a human touch.

Yep. Get a monkey... laugh.gif


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CWB
Posted: May 09, 2011 11:38 am
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QUOTE (MacFromOK @ May 08, 2011 05:14 pm)
QUOTE (tekwiz @ May 08, 2011 11:57 am)
It should be possible to activate any of them without a human touch.

Yep. Get a monkey... laugh.gif

surplus dell tech support employees ?
laugh.gif tongue.gif


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tekwiz
Posted: May 09, 2011 06:25 pm
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Or go to a med school & buy a finger... blink.gif


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
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Wizfinger
Posted: July 18, 2011 09:09 am
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I have been in contact with Jeff Rowberg from http://www.keyglove.net/ and he replied:

QUOTE
Capacitive touch screens work basically by detecting a difference in the electrical capacitance on the screen's surface. Human skin will cause a change, and conductive silicone (which many styluses use) will also do it.

The silver nylon fabric I'm using for the Keyglove achieves the same effect. I can guarantee that the fabric doesn't require any human skin contact. You could put it on the end of a wooden dowel and it would work on the capacitive touch screens just as well.

If you could control it this way, I think you could wrap a marble in the stuff and it would work also. I haven't tried that though. I do know that the silver nylon fabric triggers a "tap" action on my iPad as well as "drag" actions.
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CWB
Posted: July 18, 2011 12:54 pm
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you might try metalized mylar ... the kind used in those fancy gift balloons .


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Gorgon
Posted: July 18, 2011 01:54 pm
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It must be easier ways to register loose marbles? rolleyes.gif

TOK wink.gif



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zosa
Posted: July 22, 2011 06:23 am
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QUOTE (Wizfinger @ July 18, 2011 03:09 am)
I have been in contact with Jeff Rowberg from http://www.keyglove.net/ and he replied:

QUOTE
Capacitive touch screens work basically by detecting a difference in the electrical capacitance on the screen's surface. Human skin will cause a change, and conductive silicone (which many styluses use) will also do it.

The silver nylon fabric I'm using for the Keyglove achieves the same effect. I can guarantee that the fabric doesn't require any human skin contact. You could put it on the end of a wooden dowel and it would work on the capacitive touch screens just as well.

If you could control it this way, I think you could wrap a marble in the stuff and it would work also. I haven't tried that though. I do know that the silver nylon fabric triggers a "tap" action on my iPad as well as "drag" actions.

I've experimented with this a lot and have yet to find any material that will be recognized as present on the surface of an iPhone or iPad without a human body in very close (<a few mm) proximity or in direct contact. None of the materials mentioned here (silver nylon fabric, conductive mylar, conductive silicone...) will work if put at the end of a long wooden dowel. It is an easy experiment to try.

I'm curious if anyone has actually found a material that will work. I believe that you need to simulate the dielectric of a large mass of human flesh to get this to work and I know of no materials that would do this.

This is certainly open to lots of clever and funny responses...if you have any serious ideas please post them. Thanks.
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MacFromOK
Posted: July 22, 2011 08:21 am
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How about an actual capacitor? huh.gif


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CWB
Posted: July 22, 2011 11:22 am
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hmmm ...
if you could describe the actual developmental application/end use this may help in figuring out a solution .
for example , if the "ball on a stick" is to be used as an assist to limited mobility individuals then a conductive strip/wire in the stick might work .


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GPG
Posted: July 22, 2011 01:27 pm
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^ Yes, there are a few touch screen technologies, human capacitance is not one of the leaders.
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Wizfinger
Posted: July 22, 2011 01:43 pm
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The application will be to position items on the screen and the let go of them. (like a chess board). This means the human hand, or indeed the entire body, will not be in contact with the item that is placed on the screen.

Another application will be to roll a real physical marble over the iPad screen and detect it's position, without it being touched.
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GPG
Posted: July 22, 2011 01:56 pm
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Then you want an acoustic one. Google acoustic touch screen
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zosa
Posted: July 22, 2011 03:08 pm
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....or IR or another "imaging" modaility

But is there any material that will work with (arguably) the current most widely distributed Consumer Electronics touch screen technology, Capacitive (ie iPhone, iPod Touch, iPad)?
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CWB
Posted: July 23, 2011 11:41 am
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a few years back i seen *something* about a touch pad that used resistive X/Y determination .



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GPG
Posted: July 23, 2011 12:15 pm
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^Yes, they exist too. Basically, apply a voltage across X and measure the voltage on Y (floating). Then swap to voltage across Y and measure X. This gives X,Y coordinates.
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jrowberg
Posted: September 03, 2011 10:51 pm
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QUOTE (zosa @ July 22, 2011 01:23 am)
QUOTE (Wizfinger @ July 18, 2011 03:09 am)
I have been in contact with Jeff Rowberg from http://www.keyglove.net/ and he replied:

QUOTE
...You could put it on the end of a wooden dowel and it would work on the capacitive touch screens just as well.

If you could control it this way, I think you could wrap a marble in the stuff and it would work also. I haven't tried that though. I do know that the silver nylon fabric triggers a "tap" action on my iPad as well as "drag" actions.

As the originator of what's quoted here, I'd just like to say that it not correct (as was pointed out above). I didn't actually try the wooden dowel trick until I saw this post saying I was wrong, and lo and behold, it doesn't work the way I predicted.

While the experiments I've done don't require direct contact, the silver nylon fabric does work if the fingertip is in very close proximity. It is also possible that since, in my particular design, each fabric sensor is a floating I/O line and has a very small (but virtually constant) electrical charge on one end, this makes a difference.

But yes, the fabric all by itself, far away from any charges, does nothing on my iPad screen. I apologize for the incorrect information.
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neilybod
Posted: December 03, 2011 09:35 pm
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Funnily enough,
this post has been edited by yours truly .
honestly , i cannot figure out what the hell monkeys and bananas have to do with this topic that has been dead for quite some time .

you've got my attention .

This post has been edited by CWB on December 04, 2011 02:19 pm
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michaeldhopkins
Posted: December 31, 2011 06:51 pm
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I read this thread with interest. Is it possible to embed a battery in something (hopefully a watch battery or something similar) to trigger touch on capacitive screens? I have in mind a board game played on an ipad's screen with a few figurines, but similarly to the person who started this thread I'm having difficulty coming up with any way for the ipad to reliably detect the position of the figurines on the map.
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bananaphone_97
Posted: January 12, 2012 09:30 am
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Great news for everyone! It seems that anti static film is the best solution to operating a capacitive touch screen without the aid of human skin. Here is the link to the site that I read about this material: How To Make A Free Capacitive Stylus
There's even a video to prove that it works! (this should work great for the figurine game!)
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CWB
Posted: January 12, 2012 03:05 pm
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hmmm ...

have you tested this in a manner as the guy alluded to near the end of the video ?
"... and you have to wear gloves ..."

also , a thin covering with a soft material (cotton cloth ?) will help prevent scratching the working surface of the screen .


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Sunhammer
Posted: September 14, 2013 05:00 am
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huh.gif
I am sorry to hear that OP is not having success, and I cannot speak with authority about cr-apple products, however:

I just bought a capacitive pen stylus for my samsung galaxy tab 3. While the body is metallic (I do not know WHICH metal) the stylus end appears to be a rubber ball... at any rate, after reading the O.P. I wrapped my stylus in several layers of non-conductive material and held it as far from the screen as possible, and the stylus works fine.

tldr; at least with samsung screens there is absolutely nothing to do with the human body except for the skins ability to make micro-connections on the screen.

So, I'd ask: Are you really sure that what you think is going on really is going on?

unsure.gif
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