Parallax 28049 Pololu IR Beacon Transceiver 

The Pololu IR Beacon Transceivers are devices meant to be used in pairs to give robots a simple means for detecting each other. You can use the beacons to build pairs of robots that interact or chase one another or to make a robot that can identify and return to a home base. These beacons are ideal for autonomous robot contests in which robots compete in pairs.

The IR beacons feature round PCBs with six wide-angle emitters to provide uniform broadcasting in all directions. The on-board voltage monitoring enables more consistent output brightness over the voltage range. Most components are pre-assembled, so all you need to solder is the capacitor, connectors, and IR sensors (make sure you solder them in from the bottom of the PCB!).

The beacons work by transmitting and detecting infrared light, much like a television remote control. The beacons alternate between transmitting and receiving so that they never get confused by reflections of their own transmissions.

Interfacing to the Pololu IR Beacon is simple — it has four digital outputs that indicate which of its four sides detects the other beacon the strongest. An enable input lets you select between active mode and a low-power mode.

Features:

• Four On-board red LED's indicate the direction to the other beacon, enabling visual confirmation that the Beacons are "seeing" eachother
• Four Digital outputs, each representing a cardinal direction
• Four IR Receivers and six IR Emitters ensure a 360 degree coverage area

Application Ideas:

• Cat and Mouse Robots
• Human following robot
• Robot to robot detection

Specifications:

• PCB Size: 1.35" diameter
• Output refresh rate: 20 Hz
• Detection range: 6 inches - 20 feet
• IR Modulation Frequency: 56 kHz
• Supply Voltage: 6-16 VDC
• Data Voltage: 5 VDC
• Number of IR Detectors: 4

Note: The Pololu IR beacon is a kit; before using it, you need to assemble the beacon by soldering its components onto its circuit board. To use the kit in robotics projects, you need to connect it to your own robot controller. Please note that the IR beacons only work in pairs and that certain kinds of artificial lighting (e.g. some fluorescent lights) can interfere with the sensors.