30-03-2012, 11:57 AM
DIGITAL LOGIC AND DESIGN
29758279-Traffic-Signal-Project-Report.docx (Size: 32.05 KB / Downloads: 32)
SYNCHRONIZED TRAFFIC SIGNAL CONTROLLER
1- This controller assumes equal traffic density on the entire road.
2- This traffic controller uses digital logic, which can be easily, is implemented by logic gates.
3- This controller is generalized one can be used for different roads with slight modification.
4- All the traffic signals in this controller are synchronized with each other.
X, Y are used as binary variables to denote the four states of all the signals. Letters A to H indicate the left and right sides of roads in four directions as shown in the fig.
And the traffic movement on the roads at a specific signal (green) is denoted by arrows in directions in which traffic can flow as shown in figure.
When one signal is green the other signals, one will be yellow from which direction traffic will flow after it and other two will be red.
The Boolean function of green light of a signal will be same as the Boolean function of yellow light of the other signal through which traffic will flow after it signal and the other two red lights of remaining signals and it will be same as for other paths.
IMPLEMENTATION:-.
Timer 555 (IC1) is wired as an astable multivibrator to generate clock signal for the 4-bit counter 74160 (IC2). The time duration of IC1 can be adjusted by varying the value of resistor R1, resistor R2, or capacitor C2 of the clock circuit. The
‘on’ time duration T is given by the following relationship:
T = 0.695C2(R1+R2)
IC2 is wired as a 2-bit binary counter by connecting its pin 11’s output to clear pin 1 via inverter. Binary outputs from pins 13, 14 assumed as variables X and Y, respectively. These outputs, along with their complimentary outputs X’, Y’ respectively, are used as inputs to the rest of the logic circuit to realize various outputs satisfying Table 1. Pin 12 is grounded because we require two bit counter so to convert it into 2 bit counter. We inverted pin 11’s output and set it to clear input of counter and grounded pin 12.
We can simulate various traffic lights using green, yellow, and red LEDs and feed the outputs of the circuit.
The traffic signals can also be controlled manually, if desired. Any signal state can be established by entering the binary value corresponding to that particular state into the parallel input pins of the 2-bit counter. Similarly, the signal can be reset at any time by providing logic 0 at the reset pin (pin 1) of the counter using an external switch.