The infrared barrier sensors are a good way to detect an obstacle or a movement. A first sensor will persuader of the infra-red invisible to the naked eye, and a second will receive them. If an object cut the beam, it will be possible to detect it.

• Detection distance: about 50 cm
• Voltage: 3.3 - 5.5VDC
• Model No- SL 500
• NPN- Normally Open (NO)
• Transmitter / receiver LED Angle: 10 °
• Response time: 2 ms