# Arduino - Trigger an iPhone's touch screen with no human interaction

I'm trying to replicate part of this experiment. Specifically, I want to touch the screen with a cable and some aluminum foil whenever I send a signal from an Arduino pin. From the blog post linked above:

For communication from the Arduino to the Android tablet I'm using a relay to vary the capacitance of a aluminum foil taped to the screen. [...] A relay allows me to float the foil or pull it to ground, effectively changing the capacitance. This is much more reliable, but requires a bulky relay. I think with some more experimentation I'll be able to find a solid sate solution.

This is how my circuit looks like right now:

Basically I have a relay switch switching from ground to float every second.

This works intermittently. Sometimes the screen stops accepting real touch from fingers until the cable is disconnected from the screen.

How can I make this circuit more reliable? How can I make this cable 'touch' the screen whenever I send a signal from the Arduino board?

EDIT 1: I was able to isolate the problem a little bit. If I put my hand behind the phone, even a few milimiters away from it, the trigger works. Otherwise, it won't. See: https://vine.co/v/bIeWP0pdvuP.

EDIT 2: If I connect the charing cable to the iPhone and touch the other end (the USB shield that gets connected to the computer) it works. I tried to connect that end to ground and works intermittently. It looks like a ground problem. The arduino is connected via USB to my laptop so I guess that's where my ground comes from.

• – miguelrios Mar 31 '13 at 21:00
• Have you tried adding some capacitance and maybe a resistor parallel to the com->no pins? – drzymala Mar 31 '13 at 21:06
• The experiment you linked to was for an android phone to be used as a flashlight - I don't see the connection with your question. – Andy aka Mar 31 '13 at 21:16
• Please check your relay connections - there is an anomaly in your circuit - the contact symbol you have used doesn't match your NC label. I'm not saying you've done a mistake in the real circuit but who can tell? I think it might be OK actually. – Andy aka Mar 31 '13 at 21:56
• @Andyaka Part of that experiment is communication between the tablet and the arduino board by using 'touch'. That's exactly what I need, to 'touch' the screen programmatically. Here's an earlier version of the experiment: youtube.com/watch?v=JDgDMBquBw0 and another similar one that uses an iPhone: youtube.com/watch?v=z4eTjH4zjwE – miguelrios Mar 31 '13 at 22:51