Comments: Installing an Arduino Library

On a Mac, it's also possible to install libraries the Arduino Sketchbook folder. For my Mac, that's:

/Users/root/Documents/Arduino/library

For me, I find it's better to keep the main Arduino distribution clean, and install my own stuff in my user directory.

If you are seeing this error message, then you didn't install the library correctly with your Arduino IDE:

CapacitiveSensorSketch:12: error: 'CapacitiveSensor' does not name a type
CapacitiveSensorSketch:13: error: 'CapacitiveSensor' does not name a type
CapacitiveSensorSketch:14: error: 'CapacitiveSensor' does not name a type
CapacitiveSensorSketch.pde: In function 'void setup()':
CapacitiveSensorSketch:18: error: 'cs_4_2' was not declared in this scope
CapacitiveSensorSketch.pde: In function 'void loop()':
CapacitiveSensorSketch:25: error: 'cs_4_2' was not declared in this scope
CapacitiveSensorSketch:26: error: 'cs_4_6' was not declared in this scope
CapacitiveSensorSketch:27: error: 'cs_4_8' was not declared in this scope

Double check that you installed the library in the correct folder. Also, make sure close out all instances of the Arduino IDE and reopen it so Arduino can rescan the folders.