The part list consists of one Arduino, two resistors, and one IR emitter. That’s right, an emitter. When an LED (IR or otherwise) is reverse biased it can act as a light sensor.

Arduino Based Wireless Intrusion Detection Using IR Sensor and GSM Intrusion Detection Systems (IDS) strive to catch computer system intrusion & utilize by any garnering and analyzing data.

Self-balancing Arduino Does It Without An IMU. 15 Comments . by: Mike Szczys. September 26, 2013. ... The black PCB seen to the right of the robot is an IR reflectance sensor.