Simple Traffic Light Control in Multisim
Traffic Light system is used to control the vehicular traffic. In recent times, as the population is increasing, parallelly, everyone owns different types of vehicles, most of them own more than the required number of vehicles, resulting in a rise in the numbers of vehicles. That’s makes traffic lights are a necessity to avoid traffic jams and accidents. The system consists of three lights, having a different message for the drivers. The upper one is red light indicating the driver to halt at the intersection, the last light is green giving the driver permission to drive through the intersection whereas the middle one, yellow in color, alerts the driver to wait when the next light in order is red or to start the engine and get ready to go if the green light is next.
A traffic light system is a proven methodology to stop the collisions of vehicles and to control the traffic jams in today’s time where everyone owns different types of vehicles. The fundamental idea behind this project is to manage the traffic and avoid traffic jams. It also serves the purpose of avoiding vehicular collisions. This project is just a one-way traffic controller, although it can be further modified as well. The project will be designed to work in a way, it provides instruction to the drivers to drive through the intersection or halt at the intersection. With this project, we aim to build a traffic light system that can efficiently control the traffic too.
Components
1. 555 timer IC — 555_virtual
2. 4017 IC — 4017BP_10V[CMOS_10V_IC]
3. Diodes — 1N4148
4. 9V Battery
5. 100k, 22k, 500k, and 100-ohm resistors
6. 0.1µF and 2.2µF capacitors
7. LEDs — red, green, and yellow
This traffic light system is made without a microcontroller.
Components Details
IC 4017
It is a CMOS decade counter. It counts from 0–10 and the output is decoded. Pin 1–7 and 9–11 are the 10 output pins. Pin 8 is connected to the ground of the circuit. Pin 12(carry out) is used as carry while counting. Pin 14 is connected to the 555 timer. Pin 15 is used to reset the count to 1. Pin 16 is VDD or VCC. Pin 13(clock enable) is an input that holds the count when high.
555 TIMER IC
Here we are operating in the astable mode. Pin 2(Trigger) — turns on output when supplied voltage is less than 1/3(VCC). Pin 6(Threshold) — turns off output when supplied voltage is more than 2/3(VCC). Pin 7(Discharge) — for low output voltage, C1=0.01µF is discharged to the ground. The threshold pin and trigger pin are connected to C1, which means that they have the same voltage. At the beginning of the cycle, the threshold pin is low and the discharge pin is off. So current flows through R1 and R2 and charges C1. When it charges to 2/3 VCC, the output is switched off by the threshold pin, and the discharge pin switches on and discharges C1. When it reaches 1/3 VCC, the discharge pin is turned on and C1 starts charging again.
Circuit Design
Connect all the components according to this schematic.
The circuit starts with a dc supply of 9V that is provided to the IC 555 VIRTUAL TIMER, working in astable mode. The timer is used in an astable mode to make sure we can control the inner circuitry of the timer (basically capacitors) to increase the time period. To control the time period of the wave generated we use a resistor connected to the discharge pin of the timer on one end and another end to the threshold and trigger pin shorted together. On increasing the value of resistance, the time period of the pulse increases, and vice versa.
By doing the calculations we can hence find the perfect value of resistance, for the required time period.
When the timer is operating in astable mode the frequency of the output waveform can be calculated by the simple formula.
The output waveform of a timer in astable mode:
From the waveform the following points can be concluded:
Period of output waveform: t = tON + tOFF = 0.693 C (R1 + 2R2)
Output High state Duration: tON = 0.693 C (R1 + R2)
Output Low state Duration: tOFF = 0.693 C R2
Duty cycle:[tON/(tON + tOFF)] = [(R1+R2) / (R1+2R2)] x 100%
Pulse repetition frequency: P.R.F = 1.44/[C(R1 + 2R2)]
In the above formulas t is time is seconds,C is the capacitance used in Farads, and R1and R2 are in ohm.
In case R1 = R2 the duty cycle equation becomes
[tON/(tON + tOFF)] = [(R + R) / (R+2R)] x 100% = 67%
By changing the values of R1, R2 & C the Pulse repetition frequency of the 555 astable multivibrator circuit output can be changed.
The output of the timer is given to the decade counter by connecting the output pin of the timer to pin 14 of the decade counter. The decade counter has 10 output pins o0-o9 which give output for one pulse each. We also have pin 12 which is used to cascade 2-decade counters to increase the count to 20 pulses, however, cascading more than 2 counters results in reducing the efficiency of the circuit. Pin o0-o3 are attached to 1N4017 diode each and then they are shorted, making it an OR gate and finally connected to red led. Pin o4- o5 and passed through diodes, shorted, and connected to yellow led. In the same fashion pins, o6-o9 are connected to green led. For the first 4 pulses, one of the inputs from o0–03 is active sequentially hence red led glows. For the next two pulses, the yellow led glows, and then the green led for the next4 pulses. The diodes are attached to prevent the circuit from shortening as it blocks the output for the pins when it is not forward biased. Each led is connected to a resistor before being grounded to provide a sink and prevent the circuit from burning.
Result
Now click on the simulation button on the top and you are done with your basic traffic light system. In case of a convergence issue, click on solve convergence to let Multisim resolve the issue.
Once the circuit run you will get the system with all three led blinking in sequential order.
Conclusion
Hence, we have constructed a simple traffic light control system. This system can be improved by adding a potentiometer instead of R1 that can control the display time for each LED according to need and also by adding a transformer for conversion from AC to DC voltage that allows this circuit to work in real-life applications. It can be further improved by using a density-based traffic control system with the help of a microcontroller.
