16-07-2012, 01:06 PM
Applications of Decoder in Traffic Light Controller
[attachment=27723]
Introduction:
Traffic signal controller is playing more and more important role in modern managemenet and controls of urban traffic to reduce the accident and traffic jam in the road.
The traffic light controller is a sequential machine to be analyzed and programmed through a multi-step process.
Decoders:
Decoders are the digital circuits that detects the presence of a specified combination of bits on its inputs and indicates the presence of the code by a specified output level.
In its general form, a decoder has n input lines to handle n bits and from one to 2^n output lines to indicate the presence of one or more n-bit combinations.
Control signals:
The control signals are 3-lights:
Top light is RED(Stop).
Middle light is YELLOW(Wait).
Bottom light is GREEN(Go).
General flow of circuit:
The system has four states, so a
Logic circuit is needed to control
the sequence of states. Also
circuits are needed to generate
the proper time intervals of 24s
and 4s that are required in a
system and to generate a clock
signal for cycling the system.
Developing the block diagram:
The system must control six different pairs of lights. These are red, yellow, and green lights for both directions on the main street and on the side streets. The system has four states so as a logic circuit is needed to control the sequence of states. Logic circuits are also needed to determine which of the four states the system is in at any given time, to generate the proper outputs to the lights and to initiate long and short time intervals.
The state diagram:
A state diagram graphically shows the sequence of states in a system and the conditions for each state and for transitions from one state to the next.
[attachment=27723]
Introduction:
Traffic signal controller is playing more and more important role in modern managemenet and controls of urban traffic to reduce the accident and traffic jam in the road.
The traffic light controller is a sequential machine to be analyzed and programmed through a multi-step process.
Decoders:
Decoders are the digital circuits that detects the presence of a specified combination of bits on its inputs and indicates the presence of the code by a specified output level.
In its general form, a decoder has n input lines to handle n bits and from one to 2^n output lines to indicate the presence of one or more n-bit combinations.
Control signals:
The control signals are 3-lights:
Top light is RED(Stop).
Middle light is YELLOW(Wait).
Bottom light is GREEN(Go).
General flow of circuit:
The system has four states, so a
Logic circuit is needed to control
the sequence of states. Also
circuits are needed to generate
the proper time intervals of 24s
and 4s that are required in a
system and to generate a clock
signal for cycling the system.
Developing the block diagram:
The system must control six different pairs of lights. These are red, yellow, and green lights for both directions on the main street and on the side streets. The system has four states so as a logic circuit is needed to control the sequence of states. Logic circuits are also needed to determine which of the four states the system is in at any given time, to generate the proper outputs to the lights and to initiate long and short time intervals.
The state diagram:
A state diagram graphically shows the sequence of states in a system and the conditions for each state and for transitions from one state to the next.