Need to Make a Touchpad with Microcontrollers? Here it is, Without Further Components

By admin, January 18, 2012

Do you need to make a simple touchpad?

Try doing it with the analog port of microcontrollers. We did it successfully with the Microchip 16F and 18F4550 families.
The trick is that: define the analog Ax port as output, and send 1 (or the maximum value) to this port. After that, send zero (0), and configure this port as Input, and do an immediatelly read. Considering an 8-bit analog port, if there is a value over 127, there is a hand there.

It work with a 2 x 2 cm square designed in a PCB, Intern side is ground, and external is linked to the microcontroller. The links are maximum 20 cm away from the microcontroller.

You may adjust it by doing the sensor area with 4 square centimeters. For other values, you must test new values e interferences for not detecting any erroneous states.

If you need any guidance on int, feel free to contact me. You may also find further information about this subject in English by visiting Servo-Actuated Door Keylock Hack with capacitance touch-pad

Thanks to Giorgos Lazaridis and Caio Cesar Alvarez Kissajikian.