Traffic Light Controller Using 8051 Pdf Download

Traffic signals operate in either pre-timed or actuated mode or some combination of the two. Pre-timed control consists of a series of intervals that are fixed in duration. Collectively, the preset green, yellow, and red intervals result in a deterministic sequence and fixed cycle length for the intersection. In contrast to pre-timed control, actuated control consists of intervals that are called and extended in response to vehicle detectors. Detection is used to provide information about traffic demand to the controller. The duration of each phase is determined by detector input and corresponding controller parameters. Actuated control can be characterized as fully-actuated or semi-actuated, depending on the number of traffic movements that are detected. Table 5-1 summarizes the general attributes of each mode of operation to aid in the determination of the most appropriate type of traffic signal control for an intersection. The attributes of the various modes of operation are discussed in additional detail in the following subsections.

traffic light controller using 8051 pdf download

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Semi-actuated control has several advantages. Its primary advantage is that it can be used effectively in a coordinated signal system. Also, relative to pre-timed control, it reduces the delay incurred by the major-road through movements (i.e., the movements associated with the non-actuated phases) during periods of light traffic. Finally, it does not require detectors for the major-road through movement phases and hence, its operation is not compromised by the failure of these detectors.

Fully-actuated control refers to intersections for which all phases are actuated and hence, it requires detection for all traffic movements. Fully-actuated control is ideally suited to isolated intersections where the traffic demands and patterns vary widely during the course of the day. Most modern controllers in coordinated signal systems can be programmed to operate in a fully-actuated mode during low-volume periods where the system is operating in a "free" (or non-coordinated) mode. Fully-actuated control can also improve performance at intersections with lower volumes that are located at the boundary of a coordinated system and do not impact progression of the system (). 4Fully-actuated control has also been used at the intersection of two arterials to optimize green time allocation in a critical intersection control method.

There are several advantages of fully-actuated control. First, it reduces delay relative to pre-timed control by being highly responsive to traffic demand and to changes in traffic pattern. In addition, detection information allows the cycle time to be efficiently allocated on a cycle-by-cycle basis. Finally, it allows phases to be skipped if there is no call for service, thereby allowing the controller to reallocate the unused time to a subsequent phase.

The vehicular green interval is the time dedicated to serving vehicular traffic with a green indication. This interval is defined primarily by the minimum and maximum green parameters in the case of an isolated intersection. At an actuated controller, other parameters (e.g., passage time) also determine the length of this interval. Those parameters are discussed in Section 5.4. It is also possible that the duration of the vehicle green interval may be defined by the length of the associated pedestrian intervals.

The soft recall parameter causes the controller to place a call for vehicle service on the phase in the absence of a serviceable conflicting call. When the phase is displaying its green indication, the controller serves the phase only until the minimum green interval times out. The phase can be extended if actuations are received. This may be used during periods of low traffic when there is a desire to default to the major street.

The gap reduction feature reduces the passage time to a smaller value while the phase is green. Initially, the gap sought between actuations is the passage time value. Then, after a specified time (Time Before Reduction), the passage timer is reduced to a minimum gap using a gradual reduction over a specified time (Time To Reduce). This functionality is achieved by programming the following controller parameters: time before reduction, time to reduce, and minimum gap. Their relationship is shown in Figure 5-5.

Variable initial is used in some cases to ensure that all vehicles queued between the stop line and the nearest upstream detector are served. Variable initial uses detector activity to determine a minimum green. Vehicles arriving on red that are not able to reach the upstream detector due to a standing queue will be detected and will extend the green by an amount sufficient to allow them to be served using the passage time. This feature is applicable when there are one or more advance detectors, no stop-line detection, and wide fluctuations in traffic volumes between peak and off-peak hours. Variable initial timing is achieved by programming the following controller parameters: minimum green, added initial, and maximum initial. Their relationship is shown in Figure 5-6.

A common policy for selecting the added-initial parameter is to set this value at approximately 2.0 seconds per actuation if the phase serves only one traffic lane, 1.5 seconds per actuation if it serves two traffic lanes, and 1.2 seconds per actuation if it serves three or more lanes. Slightly larger values can be used if the approach has a significant upgrade or a significant number of heavy trucks. Bicycle traffic may also warrant higher values depending on the intersection width. Some agencies have developed more specific calculations for determining the added initial parameter. For example, the Los Angeles Department of Transportation uses Equation 5-4 to calculate the added initial setting.

A delay parameter can be used to postpone a vehicle actuation for a detector input on a phase. By using a delay timer, an actuation is not made available until the delay timer expires and the actuation channel input is still active (i.e., the detection zone is still occupied). Once an actuation is made available to the controller, it is continued for as long as the channel input is active. Application of the delay timer is illustrated in Figure 5-7.

A detector can be configured as a queue service detector to effectively extend the green interval until the queue is served, at which time it is deactivated until the start of the next conflicting phase. This functionality is offered as a parameter in most modern controllers. However, if it is not available as a parameter, equivalent functionality can be acquired by using the features of many modern detector amplifiers.

The LEDs get automatically switched on and off by making the corresponding port pins of the microcontroller high, based on the 8051 microcontroller and its programming done by using KEIL software. At a particular period of time, only the green light holds ON and the other lights remains OFF, and after sometime, the changeover traffic light control from green to red takes place by making the succeeding change for glowing of yellow LED. This process continues as a cycle and the timing for changing the LEDs can be displayed with the use of a seven-segment LED display in this projectThis traffic light control system can be further enhanced in such a way to control the traffic signals automatically based on the traffic density on roads with the help of IR sensor modules with automatic turnoff if there are no vehicles on either side of the road which leads to power consumption.

Density Based Traffic Signal SystemA prototype of traffic light control system is made by using Infra-Red sensors along with major components Microcontroller and LEDs which are used for controlling traffic signals based on the density of the traffic. The junction taken into consideration is a four-side junction with the traffic flow on each side is only in one direction. This traffic light control system consists of the following three main components:

After going through this article I remembered my project which I made in my final year!!!We were a group of 3 friends made an automated car parking system using microcontrollers.Thanks for taking me back to my old memories!!

Traffic lights are signaling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic. An actual traffic light alternates the right way of road users by displaying lights of a standard color (red, yellow/amber, and green), using a universal color code (and a precise sequence to enable comprehension by those who are color blind). In the typical sequence of colored light, (1) illumination of the green light allows traffic to proceed in the direction denoted; (2) illumination of the yellow/amber light denoting ready to proceed in the direction denoted; and (3) illumination of the red signal prohibits any traffic from proceeding. Usually, the red light contains some orange in its hue, and the green light contains some blue, for the benefit of people with red-green color blindness, and green lights in many areas are in fact blue lenses on a yellow light (which together appear green). Program was written for the MDE trainer kit to control the outputs of the microcontroller in a given sequence. Green and red light-emitting diodes (LEDs) are connected to the microcontroller outputs. First, the assembly language programs were written to turn on only one LED and then turn off the same LED. Next, the program is improved by making the LED blink, and then, the input switches are read. The walk push button and the other indicating a car at the crossing light are turned on. As switches are mechanical objects, some de-bounce time (timer programmed dead time of 50 ms) is also placed in the program. The light is controlled as long as each LED with one switch is pressed, and the LED is ON and when the switch is not depressed, the LED is OFF. Then, the LED will be made to blink once per second as long as the associated switch is ON. Finally, the program is improved when a subroutine is added where the traffic light controller is on green or red stays ON while the corresponding switch is ON. If more than one switch is activated, then the ON is for the red light. The LEDs simulate the traffic lights and switches simulate the walk push button and the car presence sensor at a crossroad. 2ff7e9595c