Capacitive touch panel detecting false touch

Thread Starter

BoopathiS

Joined Jan 21, 2020
2
Hi All,
I'm using capacitive touch panel LCD for my project. My project does not have earth connection. Due to this, touch panel detecting false touch frequently. Touch panel having FT5446 touch controller.

1) When connecting LCD casing to earth terminal, touch is working properly.
2) Connected to different power supplies without earth, touch function is not working.
3) Connected to battery, touch function is working properly.

Due to project requirement i can't use earth. Can anyone give me some suggestion to overcome this issue.
 

Sensacell

Joined Jun 19, 2012
2,567
Capacitive sense systems can be sensitive to noise generated from switch mode power supplies, the noise spectrum overlaps with the sensor frequencies.

You stated that the system works with a battery- this would indicate that the required sensor current return path is good.

Try a linear PSU or a different brand of switcher- some are better than others in this regard.
 

KeithWalker

Joined Jul 10, 2017
797
A capacitive touch sensor works by detecting the capacitance between the sensor and circuit common of the power supply. Grounding the supply common gives a large ground plane enabling the sensor to work. Using an external battery will also give a good capacitive reference. If the sensor was placed in a metal container or was surrounded by a metal frame connected to circuit common, you would have a much better ground reference for the sensor.
Regards,
Keith
 

Thread Starter

BoopathiS

Joined Jan 21, 2020
2
Thanks to Sensacell and Keithwalker for giving more clarification on touch sensor,

1. I tried with 3 different brand of power supply units, but still touch sensor is malfunctioning.

2. Connected Touch panel metal frame to power supply ground point(DC negative voltage), still touch sensor is malfunctioning.

3. Removed other loads from SMPS and Connected only SMPS, driver board and Touch LCD unit, the issue still remains same.

I want to try with different brand of touch sensors also.
 
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