Activating a touchscreen with Arduino is driving me crazy!

For a project I'm working on I need activate the touchscreen on a phone once every five hours. I am using this on eight different phones.

I am having trouble activating the screen. Sometimes what I tried works and sometimes it does not. Ive spent probably about ten hours with various materials to get an accurate key press but nothing works consistently on all eight phones.

How can I can consistently stimulate a touchscreen press on a cell phone touch screen or at least make my method more consistent.

My circuit is a relay that makes the connection between a large sheet of aluminum tin foil under the cell phone and a penny on top of a rectangular piece of foil touching the screen.

That must mean your touch screen activation is not working consistently across different phones. Do you have to use foil or can you use a small servo motor with a touch screen stylus to activate the screen? Most phone screens turn off after certain time of inactivity.