I am going to be working on a new design and we wanted to add capacitive touch capability to our board.
We wanted to etch a copper pad on the board and then use this as the touch element. After doing some research it looks like this is the approach:1.) Have a digital output of the micro controller toggle a pin high and low.
2.) This digital output is connected to a resistor that is then connected to the copper touch electrode. This is creating the RC time constant.3.) The electrode is then connected to an input of the microcontroller.
4.) After I set the digital output high in step 1 I should start the counter.5.) I then count until I have reached a certain threshold. I will be sampling the input using the ADC.
6.) If the counter is higher than the untouched state to reach the threshold then there has been a touch.
Does this sound correct?
Does anyone have any information on what the geometry of the touch electrode should be?