touchscreen unresponsive when phone is on flat surface

Yeah, there are a few discussions about this on the forums already. It's most likely a capacitance issue. When your phone is just sitting on a table and you touch the display, you may not create enough capacitance with the touchscreen for it to register as a touch (as opposed to resistive touchscreens which needed only physical contact but were less accurate as a result). Touching the body of the phone basically creates a common ground or voltage reference point for the phone, allowing your finger to create the needed amount of capacitance (in technical terms, no longer a floating ground). Whenever I touch the screen while the phone is lying on a table, I just always make sure to rest either my thumb or ring finger on one of the edges.

A lot of factors will also come into play---whether or not your phone is in a case, type of material the phone is resting on, the level of humidity in the air, even potentially the type of shoes you are wearing. This is why sometimes it works and sometimes it doesn't.

sometimes my phones touchscreen becomes unresponsive when its flat on its back on a table for example. I unlock the screen with the trackpad or power button so that the screen comes on. Then when i try to slide the lockscreen it doesnt do anything. When i begin sliding the bar from the total edge of the screen it sometimes works.
Usually i just have to pick up the phone to get the touchscreen working again. actually, when i even lift up the phone the slightest bit, it works again.

Weird right?
anyone else experiences this issue ?

dhkr123 said:

It is not "mostly" true, it is PRECISELY true.

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No reason for the condescending tone in every post (or if it's not your intention to be condescending, you may want to restrain your constant use of caps). You had stated:

dhkr123 said:

This means that when you touch the screen, your finger is actually COMPLETING AN ELECTRIC CIRCUIT.

When the phone is lying on a table and you touch it, you are NOT completing the circuit since you are NOT touching the phone's body.

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Someone was just pointing out that if this was "precisely" true as you put it, then the screen should never be responsive if you aren't touching the phone's body (since the circuit is, based on your reasoning, still broken). This isn't the case though since it does work sometimes. How could your statement be precisely true if it's known to be false sometimes (hence the "mostly true" comment)?

And it's actually not true. You are not completing an electric circuit. No current flows from your finger into the screen and no components within the phone are electrically coupled because of your touch. As you stated, you are altering the electric field when you touch the screen. This results in a change in capacitance in that area. Note, this change occurs even when you are not touching the phone's body, just to a different degree. Touching the phone will typically increase the amount of capacitance as opposed to when you are not though (since you are basically "grounding" yourself to the phone). The more capacitance there is, the easier it is to measure. If there is too little capacitance, the touchscreen's microcontroller will not register the change at all. Even if it does register the change, there will be additional filtering that occurs to that raw data either in the microcontroller itself or in software (or both).

This is why the screen works sometimes when you touch it without touching the rest of the phone. You are still causing a change in capacitance. The amount of change depends on numerous factors (this is what I stated in an earlier post). These factors effect how grounded both you and the phone are relative to earth ground (in the electrical sense, not geographical). Typically speaking though, if you are relatively close to earth ground, then you will be able to use the screen without touching the body of the phone. For example, someone stated earlier that the screen doesn't work when it's cold. Cold weather results in lower humidity/drier air and you being less grounded (basically why people see an increase in static electricity as well). Chances are that the touchscreen would work again without the touching the phone's body if you had physically been touching a large piece of metal with your other hand (to help ground you).

So in response to the other question posed, yes, technically by raising the voltage level to the touchscreen, it may result in a more sensitive screen since there will be a larger increase in capacitance when you touch it. It may also reduce the life of the touchscreen though, if not damage it completely, so not a good idea. It would be better to figure out the filtering mechanism if possible and adjust that in software. Not sure if any devs have looked into it (though my guess is that if it was simple, it would have been done already).