29-10-2012, 06:00 PM
SPEED CHECKER FOR HIGHWAYS
SPEED CHECKER.doc (Size: 840.5 KB / Downloads: 113)
ABSTRACT
• To Design a circuit of a electronic speed checker for vehicle system.
• Develop new ideas to implement this circuit purposely.
• To study the circuitry and different types of components & infrared LED, photodiode, 89C51 microcontroller and LCD display in the circuit.
While driving on highways, motorists should not exceed the maximum speed limit permitted for their vehicle However, accidents keep occurring due to speed violations since the drivers tend to ignore their speedometers.
This speed checker will come handy for the highway traffic police as it will not only provide a digital display in accordance with a vehicle’s speed but also sound an alarm if the vehicle exceeds the permissible speed for the highway.
The system basically comprises two infrared transmitter-photodiode sensor pairs, which are installed on the highway 100 metres apart, with the transmitter and the photodiode sensor of each pair on the opposite sides of the road. The installation of infrareds and photodiode is shown in Fig. The system displays the time taken by the vehicle in crossing this 100m distances from one pair to the other with a resolution of 0.01 second.
CONSTRUCTION AND WORKING
In the circuit, use long wires for connecting the two photodiode, so that you can take them out of the PCB and install on one side of the highway, 100 metres apart. Install the two infrared LED transmitters (such as laser torches) on the other side of the highway exactly opposite to the photodiodes such that infrared led light falls directly on the photodiodes. When any vehicle crosses the first infrared light, photodiode1 will start time. The output of 89c51 for the time set to cross 100 meters and LED1 glows during for period. When the vehicle crosses the second infrared light, stops the time for this period.
The counter starts counting when the first laser beam is intercepted and stops when the second infrared beam is intercepted. The time taken by the vehicle to cross both the infrared beams is displayed on the LCD display. For 60 kmph speed setting, with timer frequency set at 100 Hz, if the display count is less than ‘600’, it means that the vehicle has crossed the speed limit. Reset the circuit for monitoring the speed of the next vehicle.