24-10-2016, 11:23 AM
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ABSTRACT
Traffic lights, which may also be known as stop- lights, traffic lamps, traffic signals, stop-and-go lights, are signaling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic. Traffic lights have been installed in most cities around the world. They as- sign the right of way to road users by the use of lights in standard colors (red - yellow - green), using a universal color code (and a precise sequence to enable comprehension by those who are color blind).
Typically traffic lights consist of a set of three colored lights: red, yellow and green. In a typical cycle,
Illumination of the green light allows traffic to proceed in the direction denoted
Illumination of the yellow light denoting if safe to, prepare to stop short of the intersection, and
Illumination of the red signal prohibits any traffic from proceeding.
In recent days electro-mechanical controllers are replaced by electronic circuits. The accuracy & fault tolerant drive towards electronic circuits.
This project is developed to meet the requirements of solid state traffic light controller by adopting microcontroller as the main controlling element, and led’s as the indication of light. A micro controller interfaced to LEDs provides for centralized control of the traffic signals. Micro controller is programmed in such a way as to adjust the timing and phasing of LEDs to meet changing traffic conditions. The circuit besides being reliable and compact is also cost effective.
. INTRODUCTION
Traffic congestion is a severe problem in many modern cities around the world. Traffic congestion has been causing many critical problems and challenges in the major and most populated cities. To travel to different places within the city is becoming increasingly difficult. Due to these congestion problems people lose time and miss opportunities. Traffic congestion directly impacts the companies. Due to traffic congestions there is a loss in productivity from workers, trade opportunities are lost, delivery gets delayed, and thereby the costs goes on increasing.
To solve these congestion problems, we have to build new facilities & infrastructure but at the same time make it smart. The only disadvantage of making new roads on facilities is that it makes the surroundings more congested. So for that reason we need to change the system rather than making new infrastructure twice. Therefore many countries are working to manage their existing transportation systems to improve mobility, safety and traffic flows in order to reduce the demand of vehicle use.
This project uses simple electronic components such as LED as TRAFFIC LIGHT indicator and a MICRO CONTROLLER for auto change of signal after a pre-specified time interval.
Micro controller AT89C51 is the brain of the project which initiates the traffic signal at a junction. The LED’s are automatically turned ON and OFF by making the corresponding port pin of the micro controller high. A seven segment display is also connected to display the timing of each signal. At a particular instant only one green light holds and other lights hold at red. During transition from green to red, the present group yellow LED and succeeding group yellow LED glow and then succeeding group LED changes to green. This process continues as a cycle as long as supply is maintained.
Almost all electronic circuits required DC power supply. DC power supply is a circuit which converts the Ac wave form of power lines to direct voltage of constant amplitude. An ideal regulated power supply is designed to provide a pre- determined DC voltage which is independent of the current drawn from the source. These circuits are special class of feedback amplifiers. All the benefits of 'ICs' are thus obtained: excellent performance, small size, ease of use, low cost, high and reliability.
An unregulated power supply has many disadvantages due to which it is not sufficient for many applications. Some of the disadvantages are:
Poor regulation
DC output voltage varies with the ac input
DC output voltage variation varies with temperature because of semi conductors used To over come the above disadvantages we depend up on regulated power supply. Regulated power supplies have internal short circuit protection, thermal shut down and safe operation of output transistor.
MICRO CONTROLLER UNIT
Micro-controller unit is constructed with ATMEL 89C51 Micro-controller chip. The ATMEL AT89C51 is a low power, higher performance CMOS 8-bit microcomputer with 4K bytes of flash programmable and erasable read only memory (PEROM). Its high- density non-volatile memory compatible with standard MCS-51 instruction set makes it a powerful controller that provides highly flexible and cost effective solution to control applications. Micro-controller works according to the program written in it. The program is written in such a way, so that this controller energizes or de-energizes the relays according to the information received by the pushbuttons and the sensing probe.
The 8051 series of microcontrollers are highly integrated single Chip micro computers with an 8-bit CPU, memory, interrupt controller, timers, Serial I/O and digital I/O on a single piece of silicon. The 8051 is an 8-bit Machine. Its memory is organized in bytes and practically all its instruction deal with byte quantities. It uses an Accumulator as the primary register for instruction Results. Other operands can be accessed using one of the four different addressing modes available: Register implicit, Direct, Indirect or Immediate. Operands reside in one of the five memory spaces of the 8051.
The five memory spaces of the 8051 are: Program Memory, External Data Memory, Internal Data Memory, Special Function Registers and Bit Memory.
The Program Memory space contains all the instructions, immediate data and constant tables and strings. It is principally addressed by the 16-bit Program Counter (PC), but it can also be accessed by a few instructions using the 16-bit Data Pointer (DPTR). The maximum size of the Program Memory space is 64K bytes. Several 8051 family members integrate on-chip some amount of either masked programmed ROM or EPROM as part of this memory.
The External Data Memory space contains all the variables, buffers and data structures that can't fit on-chip. It is principally addressed by the 16-bit Data Pointer (DPTR), although the first two general purpose register (R0, R1) of the currently selected register bank can access a 256-byte bank of External Data memory. The maximum size of the External Data Memory space is 64Kbytes. External data memory can only be accessed using the indirect addressing mode with the DPTR, R0 or R1.
The Internal Data Memory space is functionally the most important data memory space. It resides up to four banks of general purpose registers, the program stack, 128 bits of the 256-bit memory, and all the variables and data structures that are operated on directly by the program. The maximum size of the Internal Data Memory space is
256-bytes. However, different 8051 family members integrate different amounts of this memory space on chip.
The register implicit, indirect and direct addressing modes can be used in different parts of the Internal Data Memory space. The Special Function Register space contains all the on-chip peripheral I/O registers as well as particular registers that need program access. These registers include the Stack Pointer, the PSW and the Accumulator. The maximum number of Special Function Registers (SFR’s) is 128, though the actual number on a particular
8051 family member depends on the number and type of peripheral functions integrated on-chip.
The SFRs all have addresses greater than 127 and overlap the address space of the upper 128 bytes of the Internal Data Memory space. The two memory spaces are differentiated by addressing mode. The SFRs can only be accessed using the Direct addressing mode while the upper 128 bytes of the Internal Data Memory (if integrated on-chip) can only be accessed using the Indirect addressing mode
Principle:
When a light-emitting diode is forward biased electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence. Electroluminescence (EL) is an optical and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field. The wavelength of the light emitted, and thus its color depends on the band gap energy of the materials forming the p-n junction. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.
Construction:
LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate. Most materials used for LED production have very high refractive indices. Light extraction in LEDs is an important aspect of LED production.
4.2.4 SEVEN SEGMENT DISPLAY
A seven-segment display, is a electronic display device for displaying decimal numerals. A seven segment display is composed of seven elements. Individually on or off, they can be combined to produce simplified representations of the Arabic numerals.
The set values and the selected time intervals are shown on the 7- segment display. There are two types of displays available. They are:
i. Common Cathode
ii. Common Anode
In Common Cathode type display all the cathodes of the segments are tied together and connected to ground. The supply will be given to the required segment from the decoder or driver.
FUTURE SCOPE
This project can be enhanced in such away as to control automatically the signals depending on the traffic density on the roads using sensors like IR detector/receiver module extended with automatic turn off when no vehicles are running on any side of the road which helps in power consumption saving.
This proximity detector using an infrared detector shown in fig.1 can be used in various equipment like automatic door openers and burglar alarms. The circuit primarily consists of an infrared transmitter and an infrared receiver. The transmitter section consists of a 555 timer IC functioning in astable mode. It is wired as shown in the fig. 2. The output from astable is fed to an infrared LED via resistor R4, which limits its operating current. This circuit provides a frequency output of 38 kHz at 50 per cent duty cycle, which is required for the infrared detector/receiver module.
The receiver section comprises an infrared receiver module, a 555 monostable multivibrator, and an LED indicator. Upon reception of infrared signals, 555 timer (mono) turns on and remains on as long as infrared signals are received. When the signals are interrupted, the mono goes off after a few seconds (period=1.1 R7xC6) depending upon the value of R7-C6 combination. Thus if R7=470 kilo-ohms and C6=4.7μF, the mono period will be around 2.5 seconds.
Both the transmitter and the receiver parts can be mounted on a single breadboard or PCB. The infrared receiver must be placed behind the infrared LED to avoid false indication due to infrared leakage. An object moving nearby actually reflects the infrared rays emitted by the infrared LED. The infrared receiver has sensitivity angle (lobe) of 0-60 degrees, hence when the reflected IR ray is sensed, the mono in the receiver part is triggered. The output from the mono may be used in any desired fashion. For example, it can be used to turn on a light when a person comes nearby by energizing a relay. The light would automatically turn off after some time as the person moves away and the mono pulse period is over. The sensitivity of the detector depends on current-limiting resistor R4 in series with the infrared LED. Range is approximately 40 cm. For 20-ohm value of R4 the object at 25 cm can be sensed, while for 30-ohm value of R4 the sensing range reduces by 22.5 cm.
ABSTRACT
Traffic lights, which may also be known as stop- lights, traffic lamps, traffic signals, stop-and-go lights, are signaling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic. Traffic lights have been installed in most cities around the world. They as- sign the right of way to road users by the use of lights in standard colors (red - yellow - green), using a universal color code (and a precise sequence to enable comprehension by those who are color blind).
Typically traffic lights consist of a set of three colored lights: red, yellow and green. In a typical cycle,
Illumination of the green light allows traffic to proceed in the direction denoted
Illumination of the yellow light denoting if safe to, prepare to stop short of the intersection, and
Illumination of the red signal prohibits any traffic from proceeding.
In recent days electro-mechanical controllers are replaced by electronic circuits. The accuracy & fault tolerant drive towards electronic circuits.
This project is developed to meet the requirements of solid state traffic light controller by adopting microcontroller as the main controlling element, and led’s as the indication of light. A micro controller interfaced to LEDs provides for centralized control of the traffic signals. Micro controller is programmed in such a way as to adjust the timing and phasing of LEDs to meet changing traffic conditions. The circuit besides being reliable and compact is also cost effective.
. INTRODUCTION
Traffic congestion is a severe problem in many modern cities around the world. Traffic congestion has been causing many critical problems and challenges in the major and most populated cities. To travel to different places within the city is becoming increasingly difficult. Due to these congestion problems people lose time and miss opportunities. Traffic congestion directly impacts the companies. Due to traffic congestions there is a loss in productivity from workers, trade opportunities are lost, delivery gets delayed, and thereby the costs goes on increasing.
To solve these congestion problems, we have to build new facilities & infrastructure but at the same time make it smart. The only disadvantage of making new roads on facilities is that it makes the surroundings more congested. So for that reason we need to change the system rather than making new infrastructure twice. Therefore many countries are working to manage their existing transportation systems to improve mobility, safety and traffic flows in order to reduce the demand of vehicle use.
This project uses simple electronic components such as LED as TRAFFIC LIGHT indicator and a MICRO CONTROLLER for auto change of signal after a pre-specified time interval.
Micro controller AT89C51 is the brain of the project which initiates the traffic signal at a junction. The LED’s are automatically turned ON and OFF by making the corresponding port pin of the micro controller high. A seven segment display is also connected to display the timing of each signal. At a particular instant only one green light holds and other lights hold at red. During transition from green to red, the present group yellow LED and succeeding group yellow LED glow and then succeeding group LED changes to green. This process continues as a cycle as long as supply is maintained.
Almost all electronic circuits required DC power supply. DC power supply is a circuit which converts the Ac wave form of power lines to direct voltage of constant amplitude. An ideal regulated power supply is designed to provide a pre- determined DC voltage which is independent of the current drawn from the source. These circuits are special class of feedback amplifiers. All the benefits of 'ICs' are thus obtained: excellent performance, small size, ease of use, low cost, high and reliability.
An unregulated power supply has many disadvantages due to which it is not sufficient for many applications. Some of the disadvantages are:
Poor regulation
DC output voltage varies with the ac input
DC output voltage variation varies with temperature because of semi conductors used To over come the above disadvantages we depend up on regulated power supply. Regulated power supplies have internal short circuit protection, thermal shut down and safe operation of output transistor.
MICRO CONTROLLER UNIT
Micro-controller unit is constructed with ATMEL 89C51 Micro-controller chip. The ATMEL AT89C51 is a low power, higher performance CMOS 8-bit microcomputer with 4K bytes of flash programmable and erasable read only memory (PEROM). Its high- density non-volatile memory compatible with standard MCS-51 instruction set makes it a powerful controller that provides highly flexible and cost effective solution to control applications. Micro-controller works according to the program written in it. The program is written in such a way, so that this controller energizes or de-energizes the relays according to the information received by the pushbuttons and the sensing probe.
The 8051 series of microcontrollers are highly integrated single Chip micro computers with an 8-bit CPU, memory, interrupt controller, timers, Serial I/O and digital I/O on a single piece of silicon. The 8051 is an 8-bit Machine. Its memory is organized in bytes and practically all its instruction deal with byte quantities. It uses an Accumulator as the primary register for instruction Results. Other operands can be accessed using one of the four different addressing modes available: Register implicit, Direct, Indirect or Immediate. Operands reside in one of the five memory spaces of the 8051.
The five memory spaces of the 8051 are: Program Memory, External Data Memory, Internal Data Memory, Special Function Registers and Bit Memory.
The Program Memory space contains all the instructions, immediate data and constant tables and strings. It is principally addressed by the 16-bit Program Counter (PC), but it can also be accessed by a few instructions using the 16-bit Data Pointer (DPTR). The maximum size of the Program Memory space is 64K bytes. Several 8051 family members integrate on-chip some amount of either masked programmed ROM or EPROM as part of this memory.
The External Data Memory space contains all the variables, buffers and data structures that can't fit on-chip. It is principally addressed by the 16-bit Data Pointer (DPTR), although the first two general purpose register (R0, R1) of the currently selected register bank can access a 256-byte bank of External Data memory. The maximum size of the External Data Memory space is 64Kbytes. External data memory can only be accessed using the indirect addressing mode with the DPTR, R0 or R1.
The Internal Data Memory space is functionally the most important data memory space. It resides up to four banks of general purpose registers, the program stack, 128 bits of the 256-bit memory, and all the variables and data structures that are operated on directly by the program. The maximum size of the Internal Data Memory space is
256-bytes. However, different 8051 family members integrate different amounts of this memory space on chip.
The register implicit, indirect and direct addressing modes can be used in different parts of the Internal Data Memory space. The Special Function Register space contains all the on-chip peripheral I/O registers as well as particular registers that need program access. These registers include the Stack Pointer, the PSW and the Accumulator. The maximum number of Special Function Registers (SFR’s) is 128, though the actual number on a particular
8051 family member depends on the number and type of peripheral functions integrated on-chip.
The SFRs all have addresses greater than 127 and overlap the address space of the upper 128 bytes of the Internal Data Memory space. The two memory spaces are differentiated by addressing mode. The SFRs can only be accessed using the Direct addressing mode while the upper 128 bytes of the Internal Data Memory (if integrated on-chip) can only be accessed using the Indirect addressing mode
Principle:
When a light-emitting diode is forward biased electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence. Electroluminescence (EL) is an optical and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field. The wavelength of the light emitted, and thus its color depends on the band gap energy of the materials forming the p-n junction. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.
Construction:
LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate. Most materials used for LED production have very high refractive indices. Light extraction in LEDs is an important aspect of LED production.
4.2.4 SEVEN SEGMENT DISPLAY
A seven-segment display, is a electronic display device for displaying decimal numerals. A seven segment display is composed of seven elements. Individually on or off, they can be combined to produce simplified representations of the Arabic numerals.
The set values and the selected time intervals are shown on the 7- segment display. There are two types of displays available. They are:
i. Common Cathode
ii. Common Anode
In Common Cathode type display all the cathodes of the segments are tied together and connected to ground. The supply will be given to the required segment from the decoder or driver.
FUTURE SCOPE
This project can be enhanced in such away as to control automatically the signals depending on the traffic density on the roads using sensors like IR detector/receiver module extended with automatic turn off when no vehicles are running on any side of the road which helps in power consumption saving.
This proximity detector using an infrared detector shown in fig.1 can be used in various equipment like automatic door openers and burglar alarms. The circuit primarily consists of an infrared transmitter and an infrared receiver. The transmitter section consists of a 555 timer IC functioning in astable mode. It is wired as shown in the fig. 2. The output from astable is fed to an infrared LED via resistor R4, which limits its operating current. This circuit provides a frequency output of 38 kHz at 50 per cent duty cycle, which is required for the infrared detector/receiver module.
The receiver section comprises an infrared receiver module, a 555 monostable multivibrator, and an LED indicator. Upon reception of infrared signals, 555 timer (mono) turns on and remains on as long as infrared signals are received. When the signals are interrupted, the mono goes off after a few seconds (period=1.1 R7xC6) depending upon the value of R7-C6 combination. Thus if R7=470 kilo-ohms and C6=4.7μF, the mono period will be around 2.5 seconds.
Both the transmitter and the receiver parts can be mounted on a single breadboard or PCB. The infrared receiver must be placed behind the infrared LED to avoid false indication due to infrared leakage. An object moving nearby actually reflects the infrared rays emitted by the infrared LED. The infrared receiver has sensitivity angle (lobe) of 0-60 degrees, hence when the reflected IR ray is sensed, the mono in the receiver part is triggered. The output from the mono may be used in any desired fashion. For example, it can be used to turn on a light when a person comes nearby by energizing a relay. The light would automatically turn off after some time as the person moves away and the mono pulse period is over. The sensitivity of the detector depends on current-limiting resistor R4 in series with the infrared LED. Range is approximately 40 cm. For 20-ohm value of R4 the object at 25 cm can be sensed, while for 30-ohm value of R4 the sensing range reduces by 22.5 cm.