Based on the SUMO competition requirements, three sensors were mandatory. These consisted of an ultrasonic sensor and two light sensors.
The ultrasonic sensor can be seen in the picture on the top left. In the competition, the sensor would be used to detect the opposing robot by determining the distance the sensor is from an object. This is determined by sending out a ping and listening for the duration it takes to return.
In the top right picture, the front and back line sensors can be seen. These based on the analog return, the colour of the ground beneath the sensors can be detected. This is how the robot stays within the arena; the arena is a black circle with a white border.