How to Implement Capacitive Touch Sensor Technology

December 1, 2016 John Magyar

Capacitive touch sensor technology example


Capacitive touch sensor technology offers an inexpensive and highly reliable alternative to the traditional mechanical switches that are used in electronics control interfaces. Manually creating or resizing a touch sensor’s complex vendor/technology-specific patterns can be both difficult and time-consuming. Fortunately, there is an automated solution, which enables the easy creation and modification of intricate touch sensor shapes.


The Inner Workings of Capacitive Touch Sensor Technology

In very basic terms, capacitive touch sensing works on the principle that, as a human finger approaches a copper-etched touch sensor electrode on a flex PCB, the capacitance of the sensor electrode changes. This change in capacitance is sensed on either a general purpose microcontroller input, or a dedicated touch control device input, connected to the sensor electrode. The microcontroller or touch control device will then update the state of one or more digital output control signals in a specific programmed response to the capacitive touch pcb design change sensed by a specific sensor electrode.

There are two different types of capacitive sensors. They are referred to as Self-Capacitance Sensing and Mutual-Capacitance Sensing.

Self-Capacitance Sensing is when the presence of a human finger increases the capacitance of a single sensor electrode. This increase in capacitance is then processed as described above.

Mutual-Capacitance Sensing occurs when the presence of a human finger decreases the mutual coupling between two sensor electrodes paired together. When this drop in capacitance (on the receive electrode) is sensed, it’s then processed as described above.


Self-Capacitance Sensing (left) and Mutual-Capacitance Sensing (right)


Implementation in Altium Designer

Touch sensor electrodes, especially the wheel sensor, have very complicated shapes. Manually creating such shapes in your PCB Design software is a tremendously challenging and time-consuming task, even for the most experienced printed circuit board designers. Now think about resizing or modifying the details of existing sensors, if needed.

Without an easy, automated way to create or modify touch sensor electrodes, it might be tough even to consider implementing touch sensors, despite their numerous advantages. Fortunately, there is an easy, automated way to do it.

Learn how to quickly implement capacitive touch screen sensor technology in Altium Designer by downloading a free white paper.


About the Author

With an emphasis on microprocessor systems design, John earned his Bachelor of Science degree from SUNY Polytechnic Institute. He initially worked as a design engineer in the Defense industry developing diagnostic test programs for complex PCBs. Subsequently, John has worked as a senior application engineer in the EDA industry supporting a wide range of ASIC, FPGA, and PCB design and verification solutions.

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