Traffic Light Project Using CD4017 Decade Counter IC

Traffic lights are useful circuits that generally serve to signal vehicular traffic in places such as highways, intersections, etc. In a simple traffic light, there are usually 3 signaling lights: Red light asks the driver to yield at the intersection, yellow light (middle one) alerts the driver to wait if the next light is red or get ready to go in case of green, whereas green light (last one) gives the driver free license to drive through the intersection. So, in this project, we are going to build a simple Traffic Light circuit using the CD4017 Decade counter IC along with an astable multivibrator circuit.

A CD4017 IC is a 16-pin CMOS decade counter/Divider with 10 outputs. It is also known as the ‘Johnson 10 stage decade counter’. It has 10 decoded outputs that give output signals one by one in sequence when a clock signal from the clock input is given.

Hardware Components

The following components are required to make Traffic Light Circuit

S.no	Component	Value	Qty
1.	Decade Counter IC	CD4017	1
2.	Transistor	2N4401, 2N4403	2, 1
3.	Resistors	22K, 5.1K, 1K, 390Ohms	1
4.	LEDs	5mm	3
5.	Diodes	1N4148	7
6.	Potentiometer	100K	1
7.	Electrolytic Capacitors	47uF, 1uF	1
8.	Breadboard	–	1
9.	Battery	9V	1

CD4017 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of CD4017

2N4403 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N4403

Traffic Light Circuit

Working Explanation

The heart of the circuit is a CD 4017 decade counter IC. The IC has 10 outputs. The IC will activate each of its outputs in a sequence manner each time a positive pulse receives on its clock pin 14. Here, an astable multivibrator circuit provides a positive clock input to the CLK pin (14) of the counter IC.

On providing CLK the counter IC starts pulsing cycles through the output pins (Q0-Q9). First, the red LED lights up, then yellow, and finally green. After which the cycle repeats continuously. The cycling time for the LEDs can be changed by tuning the 100K Pot. Here, the 1N4148 diodes protect the output LEDs from shorts.

Applications

• Traffic lights generally serve in places such as motorways, in refereeing complex industrial processes involving autonomous entities like robots.