Vehicle detection and car speed monitoring system using GMR magnetic sensors

A new simple circuit can detect the magnetic perturbation caused by the cars with two GMR magnetic field gradient sensors located on the pavement of a highway or fast road without wires. When a car passes above the board, a microcontroller processes the signal of sensors to obtain the speed and length of the car in real time. The dates of more than one thousand vehicles could be stored in a ROM until it is full. At this point the microcontroller sends the dates through a FSK modulation, that a PC stored permanently, and after present it with a software. The affordable system could be used for automatic traffic measurements and control in many places, replacing the expensive systems like the ultra sonic sensors and the video cameras to cover an extended area.