This Capacitive Touch Module uses the touch-sensing IC TTP224 to add capacitive touch to your project . Just power with 2.4 to 5.5VDC and touch the pad to activate the sensor. These touch switches interface easily to any project - with or without a microcontroller. When a capacitive load (such as a human hand) is in close proximity to the sense-pad, the sensor detects the change in capacitance and activates the switch. Custom sense-pads can be made from nearly any conductive material and these sensors can detect touch through thin layers of non-conductive materials such as glass, plastic, fabric or even wood. So, you can make this sensor hidden in the wall, tabletop and other places, which allows you to remove the conventional push-buttons troubles. There are totally 4 pads on this module, these sense-pads can be extended with wire and almost any conductive material, so that you can add 4 touch switch easily for your project.