using touchscreen on phone through a clear panel

[woodman-46]

I am not sure where to post this question on this site and so hopefully this section will be OK.
Can anyone out there tell me if it is possible to use a touchscreen on a phone (capacative or resistive ie an iphone) through a sheet of clear medium such as glass, perspex or other. Presumably the sheet has to touch the screen but how is it possible to relay the touching on the top sheet through to the actual screen of the phone so that the "commands" are registered. The simplest less technical way would be best. Any ideas welcome.
Thanks James

 

[RCinFLA]

Capacitive or electrostatic, yes. Resistive, no

 

[woodman-46]

Thanks for your reply. Can you elaborate ? How is the capacative screen still functional through a sheet of i.e glass. How does it still sense the touching through such a medium. Does it work on sensing movement and location of the finger or stylus.

Also as far as the resistive screen is concerned does it make any difference if the aforesaid sheet of glass, perspex etc is lined or coated with anything. In other words is there any way of making the resistive touchscreen sense movements or commands through such a sheet.
Thanks

 

[Noggin]

The resistive touch screen works by having two layers of electrically conductive material near each other, but not quite touching. When you press your finger on it, the two conductive layers of material touch and some analog readings can be made in order to determine where the two layers are being touched. Essentially, the layers make two voltage dividers, one in the horizontal direction and one in the vertical direction. One direction is measured and then the other. This gives X and Y coordinates. If you place a sheet of glass over the two conductive layers, then you won't be able to push on the layers to make them come into contact with each other. You might be able to get by with a clear polyester type sheet over the resistive touch screen, but I would imagine that it would reduce resolution so you'd have to make your "buttons" bigger on the display.

Someone else should elaborate on the capacitive touch screen. I've looked into them just enough to know that I'd rather use a resistive touch screen on my projects than a capacitive touch screen. However, in general, the capacitive touch screen will work through sheets of protective material, but the thinner the better.

Another alternative would be to place a sheet of glass between the LCD and the touchscreen. This introduces other problems such as not pressing exactly where you think you're pressing due to the angle and thickness of the glass.

 

[woodman-46]

Thanks for your info