Being a microcontroller based solution, capacitive touch can

also be used to drive an LED, a buzzer or to communicate

with the main processor or the rest of the system. The

necessary schematic software is provided in AN1202:

Capacitive Sensing with PIC10F.

How to Use the Board

– On the left: Higher sensitivity as a proximity sensor

– On the right: Lower sensitivity as a key

The scanning rate does not change, therefore the power

consumption remains the same in both modes.

J4 connections

seconds, the MCU will re-calibrate the sensitivity of the

key. That auto-calibration feature takes care of temperature

or humidity changes as well as a “stuck” button.

Flexibility of the Solution

The MCU can be reprogrammed using the PICkit™ 2/MPLAB®

ICD 2 connector. By having access to the source code, it is

very easy to change some values or parameters to meet your

applications’ specific needs.

size and cover material

scan rate, leaving the MCU in Sleep mode as much as

possible

software can make it faster or slower depending on the

application needs

Microc hip T e c hnology Incor porated

Capacitive mTouch™ Sensing Solutions

Overview

Touch sensing is fast becoming an alternative to traditional

push button switch user interfaces, because it requires no

mechanical movement, and it enables a completely sealed

and modern-looking design. Expanding beyond the consumer

market, touch sensing is beginning to take hold in medical,

industrial and automotive applications for reasons such as

improved aesthetics, reduced maintenance and lower cost.

Microchip’s Capacitive mTouch™ Solution is a free and easy

method to optimize your touch sensing application using a

wide variety of hardware and software resource options.

How it Works

A capacitive touch sensor is a copper pad area created on

the surface of a printed circuit board. It creates a parasitic

capacitance to ground. When a person touches the sensor,

or its covering (plastic, glass, etc.), the person’s finger

introduces an additional glass-finger-ground capacitance. That

capacitance is in parallel to the parasitic one. As capacitors in

parallel are added, a finger approaching the pad will increase

the total capacitance. This change is the criteria needed to

detect a touch.

Microcontrollers provide the ability to perform capacitive

sensing, decision making, responsive actions and other duties

pertinent to the system as well.

Capacitive Touch Implementation

The illustration below shows a simple implementation of a

single capacitive touch key. One key capacitive touch can:

action user interface

to the sensor

– Enable lower standby power consumption

– Trigger an action, like lighting up a display, without a

touch

The schematic is very simple and uses a PIC10F204/6 MCU,

a diode, a capacitor and a resistor (see the white sensing

square on the PCB).

USB Power

Connector

Jumper

J4

Jumper

J2

Connector

Sense

Pad