4 Way Traffic Signals Controller
Category: Example Projects
Designer: Talha Zaheer
Notes
4 Ways Traffic Signals with Controlled Yellow Light Delay This circuit consists of the following key elements and their functionality: The circuit is simulated in Proteus 8.17. • Clock Generation (555 Timer) (U1): Configured in a stable mode, it generates a continuous clock signal. The timing components, resistors (R5, RV1) and capacitor (C1), determine the frequency of oscillation. The output frequency of the 555 timer (f) is determined by: f = 1.44/((R5+2RV1).C1) Adjusting RV1 changes the timing interval, which modifies the duration for each traffic light. R4 limits the current to the timing capacitor C1. This signal acts as the clock input for the CD4017 counter. • CD4017 Decade Counter (U2): The CD4017 is a 10-stage decade counter. It takes the clock signal from the 555 timer (at pin 14) and sequentially activates its outputs (Q0 to Q9). Each clock pulse shifts the high signal (logic 1) to the next output pin. This sequential output controls the traffic light sequence. • LEDs (D3, D27, etc.): The LEDs represent the traffic lights (red, yellow, green). Multiple LEDs are grouped for different directions, each controlled by a transistor. • Transistors (Q1 to Q5): NPN transistors act as switches to control the LEDs. They amplify the current from the CD4017 outputs to drive the LEDs. Each transistor is connected to a specific group of LEDs. • Diodes (1N4148): Diodes ensure that signals from different outputs of the CD4017 do not interfere with one another when combined to control the LEDs. • Resistors: Current-limiting resistors are used to protect the LEDs from excessive current. Other resistors control the base current of the transistors and the timing of the 555 timer. • Switches (S1 to S4): These may simulate pedestrian crossing or manual override controls for the traffic lights. Summary Purpose: This circuit is a basic simulation of a traffic light control system for four directions. It uses the 555 timer and CD4017 IC to create a cyclic sequence of red, yellow, and green lights. Sequence: The circuit ensures that only one direction is green at a time, while the other is red. Yellow lights act as a transition between red and green. Adjustable Timing: By modifying the value of RV1, the timing of the sequence can be adjusted, simulating different traffic conditions. Additional Counter Used additional counter to reduce yellow lights delays.