Driven shield for touch sensors

colinives
Posts: 12
Joined: Tue Mar 03, 2020 2:53 pm

Driven shield for touch sensors

Postby colinives » Thu Mar 19, 2020 4:58 pm

I'm working on a product development using a touch wheel based on the ESP32 touch sensors. The ESP32 is very close behind the touch wheel and the grounded meta cover is messing with the sensitivity. I could design in a driven shield plane between the touch sensors and the ESP32 metal case but don't know where I can take an active signal from to use as the shield. I'm assuming a copy of the touch waveform would limit the effects of parasitic capacitance.

Does anyone have an idea where I can pick up a isolated waveform from the ESP32 matching the touch sensing waveform to uncouple the sensors from the ESP32 ground plane.

Thank you.

colinives
Posts: 12
Joined: Tue Mar 03, 2020 2:53 pm

Re: Driven shield for touch sensors

Postby colinives » Thu Mar 19, 2020 5:29 pm

By the way - I have previously used touch sensors which used a static DC voltage to read the touch sensor - in this situation I drove a plane behind the sensor using a DAC with the average analog sense voltage on the touch pin - this worked very well. The trouble I have with the ESP32 is that it drives a saw-tooth waveform which I can't easily replicate. I thought about using another touch sensor to drive the shield plane but the ESP32 uses time-multiplexing for driving each touch pin.

So, still looking if there is an answer to shielding the touch wheel from the ground of the ESP32.

Who is online

Users browsing this forum: No registered users and 15 guests