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This question already has an answer here:

I am doing project in which I want to perform read and write operation by using a capacitive touchscreen. What I know is I can trigger capacitive touch screen by:

  1. By using electromagnet as I heard that some of stylus works by using magnet at its point so I think electromagnet should work.
  2. By using capacitor: If I connect a capacitor's one end to vcc and other to a conductor plate then I think it will mimic the property of human finger and trigger touchscreen.

I want to use these system so I not need to make any physical changes. If I want screen to trigger then I can just charge capacitor or electromagnet. I want to know that whether my theory is correct or not and if there is any suggestion for that then let me know.

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marked as duplicate by Dave Tweed Feb 25 '18 at 12:20

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Capacitive touch screens work by altering the AC electric field on a fine grid in the phone screen that's detected as a change in capacitance at that node.

You should be able to alter the capacitance by touching the screen with a grounded electrical conductor. A quick trial with my phone shows this works.

Confirmed on EEVblog by this post."I work with capacitive touchscreens daily. When we need to control when a finger is applied to the screen, we use copper tape. The tape has a conductive adhesive that keeps it on the screen. Then, a short wire to a NO relay. When the relay is activated, it connects the copper tape to ground. This increases the response to the sensor and usually appears as a finger. I've also been looking at using a series capacitor to isolate the connecting wire from the proxy finger. "

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