When the robot will be running on a black surface with a white edge. It has to stay on the surface and not wonder off the platform on its own. Thus, it must be able to detect the white edge of the platform. This circuit is use to detection the platform of the edge. Here’s is the simple circuit diagram schematic;
Infrared Tx/Rx pair is ideal for this application because the distance between the sensors and surface will be very small if the Tx/Rx pairs were mounted under the robot. An advantage of this location is that they will not be affected by ambient lighting conditions. It is preferred that Tx/Rx pairs are used for optimum performance because the peak sensitivity wavelength of the detector are that of the emitter's.