Capacitive Touch Sensor Toggle Switch

  • Rajkumar Sharma
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Touch sensors are used in many applications, from remote controls, LED light controls to appliance control panels. This is a simple solution to replace the mechanical buttons and can be implemented in a wide variety of applications. The sensor provides great user experience. It is easy and more convenient to use as it has no moving mechanical parts. The circuit consumes very low current. Circuit has been designed using AT42QT1012 IC from microchip.  This IC has many features. The circuit shown here is just Touch On/Off Toggle switch. You can read data sheet of the IC to use the timer function. The circuit provides TTL toggle Output which can be interfaced to Microcontrollers or BC847 output that is capable to drive 5mm white LED. Use Output Pin and VCC pin to connect 5mm LED.  Small Pad on PCB helps to detect the finger touch.

Transistor can drive 100mA load and easily drive LED up too 0.5W.

The AT42QT1012 is a single key device featuring a touch on/touch off (toggle) output with a programmable auto switch-off capability. The device is One-channel Toggle-mode QTouch® Touch Sensor IC with Power Management Functions. The QT1012 features a digital burst mode charge-transfer sensor designed specifically for touch controls and a unique “green” feature – the timeout function, which can turn off power after a time delay.

Note: R5 and C3 components are optional can be used for timer operations, refer data sheet of more details. C3 replace with 0 Ohms resistor for normal toggle option.

Features

  • Supply 5V DC
  • Output TTL (Toggle)
  • Transistor output: 5V/100mA load
  • One, toggle mode (touch-on / touch-off), plus programmable auto-off delay and external cancel
  • Output Can drive 5MM White LED
  • PCB Dimensions 31.91mm x 10.78 mm

Schematic



Parts List

Connections

Photos

Video

AT42QT1012 Datasheet

40001948a

PCB

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