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Say I want to provide a device (completely batteryless of course, and detached from any human touch) the capability to immitate a touch on a capacitive screen (Galaxy S6 here). I know I just need some kind of a capacitor to touch the screen. I managed to register a touch by folding a piece of metal snack wrap (an inch square of it), put it on a piece of plastic, to escape my body's capacitiveness, and touch the screen with it. So, would I be able to do the same by connecting, let's say, an copper/aluminum foil to a capacitor, then touch the other side of that foil (or wires?) on the screen to register a touch?

I am asking about a capacitor, because I guess this would be the best/smallest solution to mimic our body's (connected to the finger) capcitiy. If I am totally wrong, and you have any other idea, welcome to suggest ;)

To make the question more clear: I want to mimic a finger (or multi touch) press, with the smallest/flattest possible (electrical?) device. I asked about a capacitor because it is small, and from my tiny knowledge in electronics, it "should do". So, this is not a general question like been asked before. I want to try and get to the specifics of how to mimic.

Thanks

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marked as duplicate by PeterJ, Michael Karas, Daniel Grillo, Null, nidhin Sep 5 '15 at 10:22

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ The fact that it's called a "capacitive touchscreen" does not mean you need a capacitance to register a touch. The coupling of a conductor (normally your finger) to a conductor in the screen is capacitive. This capacitance change is registered. See en.wikipedia.org/wiki/Capacitive_sensing \$\endgroup\$ – Bimpelrekkie Sep 4 '15 at 9:06
  • \$\begingroup\$ 1. @RogerRowland this is not a duplicate of "how..." because I am asking for a specific solution. I read that Q&A a number of times, and it was useful only to some extent. 2. If not a capacitor, how would I be able to do what I need to do without a finger? \$\endgroup\$ – rubmz Sep 4 '15 at 9:47
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    \$\begingroup\$ "Say I want to provide a device (completely batteryless of course, and detached from any human touch) the capability to immitate a touch on a capacitive screen" - well, that sounds very similar to me, hence the flag for a possible duplicate. If you look in the Related questions links, there are similar questions too: this and this \$\endgroup\$ – Roger Rowland Sep 4 '15 at 9:57
  • \$\begingroup\$ Sure, not getting into argue about this with you. Note however, that the other post you suggested has 15 answers and a more than a few comments, not a place to get answers for a more focused question... \$\endgroup\$ – rubmz Sep 4 '15 at 10:26
  • \$\begingroup\$ @rubmz You're complaining that there are too many answers?! \$\endgroup\$ – Null Sep 4 '15 at 13:39
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Capacitive touch screens are factory tested with a metal rod of a specific diameter (6mm, in my experience). I do not know what the minimum length of the rod can be, but it does not need to be as long as a finger. The rod does not need to be attached to any other circuitry or grounded. The capcitive touch mechanism works by responding to changes in the electrical properties of space in the area very close to the screen. If the diameter of the rod is too small, it will not be detected. For example, a nail or typical electric wire is too narrow for detection.

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  • \$\begingroup\$ Mmmm, interesting... (would upvote, but still can't.. newbie here). Still, how would I be able to implement capcity interference using the smallest object, and most importantly: flat. I am creating a kind of a card with 3~5 bumpers I want to press to the screen (of a known phone model) and create a multi touch event. Could this be done by using a capacitor, or should I completely resent that "capacitor" thingy"? (which I know little of, not an electronics engineer...) \$\endgroup\$ – rubmz Sep 5 '15 at 16:02
  • \$\begingroup\$ Try cutting a small aluminum foil circle and glue it to a card. It may even be possible to use a circle printed by a laser printer. The toner (ink) from a laser printer is actually carbon powder, and is somewhat conductive. But the size of the circle does matter. I would start with around 6mm. \$\endgroup\$ – mkeith Sep 5 '15 at 17:39
  • \$\begingroup\$ Sounds great, will try and report back. \$\endgroup\$ – rubmz Sep 5 '15 at 19:06
  • \$\begingroup\$ Nope, it still does not work... It may need to be in a more accurate shape, a shape which holds more capacity? \$\endgroup\$ – rubmz Sep 5 '15 at 19:13
  • \$\begingroup\$ I tried it, too. No luck. Maybe the disc would need to be connected to a bulky object for it to work. I found that even a battery doesn't work unless I am holding the battery. \$\endgroup\$ – mkeith Sep 5 '15 at 19:17

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