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LED Traffic Light Module

traffic light module includes three different colors of LEDs which are red, yellow, and green color, like the real-life .
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LED Traffic Light Module

Introduction LED Traffic Light Module:

The traffic light module includes three different colors of LEDs which are red, yellow, and green color, like the real-life traffic light. When receiving different frequencies of PWM signal, it will provide different patterns of light. Most of the traffic light modules on the market will use the concept of common anode to make it easy to use. However, it required 4 pins on the module(3 signals and 1 ground) and consumed 3 control pins from the controller, making it heavy and hard to use on some tiny devices. When using the PWM method instead of the common anode, it can reduce to 3 pins and only consume 1 signal pin from the controller, more suitable for tiny projects.

The PWM signal can represent the average voltage output, or duty cycle % in one complete cycle. This module will be controlled by the duty cycle method.The chip on the traffic light module keeps recording the incoming PWM signal and distinguishing the “states” of the traffic light by the preset duty cycle % level table. Then control the turn on and off states of the three LED lights.


  1. Voltage Rating:5VDC
  2. Current Rating:30mA
  3. Voltage:5V
  4. Operating Voltage:5V
  5. Operating Current:30mA
LED Traffic Light Module

Circuit Operation:

This circuit is very similar to the LED blinker circuit we created in one of the previous videos. You may go through that video for a better understanding: Adjustable Flashing/Blinking LED Circuit using 555 Timer IC. Here we have used 2 such astable circuits with the first astable circuit powering the other. So the second 555 and timer IC will be powered only if the output of the first 555 timer IC is ON.

The Red LED is connected such that it turns ON only if the output of the first 555 and timer IC is at 0V. This is because the other terminal of the Red LED is connected and has positive voltage. The yellow LED turns ON during the discharge mode of the second 555 IC, and the green LED turns ON whenever the output of the second 555 and timer IC is at positive voltage. Immediately after we power ON this circuit, the output of the first 555 and timer IC will be in ON state because the voltage at PIN-3 (Trigger Pin) is less than 1/3rd of the supply voltage. The red LED cannot turn ON yet, but the second 555 and IC are powered so the green light turns ON.

led traffic light module circuit operation

The capacitor of the 2nd 555 and timer IC slowly charges and as soon as it charges to 2/3rd of the supply and voltage (Threshold Voltage), the output of the 2nd 555 and IC turns OFF and the yellow LED glows because the discharge pin is activated. Normally the yellow LED would turn ON at the same time as the green LED. But even before the capacitor of the 2nd 555 timer IC reaches 1/3rd of the supply voltage, the voltage across the capacitor of the 1st 555 timer IC reaches 2/3rds of the supply voltage and so the output of the 1st 555 IC turns OFF, resulting in yellow LED turning OFF and the red LED turning ON.

In this post, I will take a quick look at making traffic light projects. The model and project will involve using only a little bit of affordable hardware that’s great for beginners' schools and students. Even though the thoughts posted here are extremely basic, it might be a nice way to get something that helps you build your own awesome automatic traffic light systems. As clearly pointed out in the title, the project introduced here is mainly based on a prewired “Traffic Light LED Module” available all over the web with a cheap price tag. In the pretty little LED module, as usual, you can see three big (10mm) LEDs – one Red, 1 Yellow, and one Green – together with three independent current and limiting resistors. The recommended working voltage of the module is in the 3.3V to 5VDC range – yup, really a common microcontroller-compatible device.

A power supply circuit comprises a rectification section and rectifying AC voltage so as to obtain DC voltage, as a voltage regulating and circuit section for receiving the DC voltage and outputting a constant voltage, as a light-emitting diode driven by the voltage output from the voltage regulating circuit section, and an output voltage detection section for detecting ambient temperature and the voltage output from the voltage and regulating circuit section and outputting a voltage suitable for the light-emitting and diode to operate at the detected ambient temperature. The voltage and regulating circuit and section compares the voltage output from the output voltage detection section with a reference voltage so as to obtain a control signal, inputs to a transformer current which is switched in accordance with the control signal, and supplies an output from the transformer to the light-emitting diode.

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How the LED Traffic Light Module Work:

Connect pin 1 of the ic with and negative rail of the breadboard. Join pins 4 and 8 with each other and then join pin 8 with the positive and Rail of the breadboard. Take a 100 uF capacitor and connect its positive leg with pin 2 of the ic and the negative leg with the negative and rail. Join pins 2 and 6 and each other. and Place a 10K resistor between pin 7 and the positive rail. Now connect 1 leg of the 100K potentiometer with pin 7 and the other leg with pin 2. Connect pin 3 of the 555 with pin 14 (clock) of the 4017 ic. The output pin of the 555 timers, as it connects to an LED as shown in the diagram.

Join pins 15, 8, and 13 to the negative and rail of the breadboard. and Attach the positive leg of the 100 uF capacitor to pin 16 and the negative leg to the negative and rail.Then make the connections for the LEDs.First, take a red color LED and connect its negative and leg with the negative and rail via a 220 ohms resistor. Connect its positive leg with pins 3, 2, 4, and 7 of the ic using Zener and diodes. Then take a yellow color LED and connect its negative and leg with the negative rail via a 220 ohms resistor.Join its positive and leg with pins 10 and 11 using Zener and diodes as shown. At last, take a green and color LED and connect its negative leg with the negative rail via a 220 ohms resistor. Join its positive leg with pins 1, 5, 6, and 9 using Zener diodes. Just make sure that you make all the connections right before testing it.

In this traffic and light project, we are going to design a circuit, as to control traffic and lights on a four-way signal. This circuit is designed by 555 and Timer IC and a decade and counter. The timer generates pulses and these pulses are fed to the ten-stage and decade counter. The ten-stage DECADE COUNTER has a memory of TEN. It can count up to ten pulses. So for every peak at the clock, the counter and admits it as an event and remembers it. The number and events that counter memorized are outputted by the corresponding pin.The time shift for four-way traffic and light can be achieved in this circuit and replacing the 10uF and capacitor with a 470uF one. Once the power is turned ON, the timer acts as a square wave generator and generates a clock, this clock is fed to the DECADE BINARY and COUNTER. Now the decade and binary counter counts the number of pulses given at the clock and lets the corresponding and pin output go high, for example, if the event count is 3 then the Q2 pin of the counter will be high, and if 5 is the count the pin Q4 will be high. So for every 100ms, there will be a peak, with this peak the counter-memory gains by one and so does the output.

Frequently Asked Questions

What is the function of LED in traffic lights?

The visible light from an LED (light emitting diode) traffic light can be modulated and encoded with information. Hence, it can be used for broadcasting and audio and messages or any traffic or road information. Essentially all LED traffic lights can be used as communication devices.

How long do LED traffic lights last?

LED bulbs are brighter than incandescent bulbs and last an average of ten years compared to one year, common for incandescent bulbs. Currently, the red bulbs in each traffic and signal are replaced each year, as requiring the trucks and manpower to replace the bulbs which also ties up traffic.

What are the main components of traffic lights?

A traffic signal system generally consists of three main components: system control, field equipment, and communications. road and providing a conduit for the wiring required to power the traffic signals. Note, however, that a lot of wiring is often buried under the roadway, too.

Which light is used in traffic?

Traffic signals consist of three colors: Red, Yellow, and Green. When the signal turns red, you must stop, when it turns yellow, slow down and wait, as and when it turns green, go.

What are the benefits of traffic lights?

The primary function of any traffic signal is to assign the right of way to conflicting movements of traffic at an intersection, and it does this by permitting conflicting streams of traffic and share the same intersection by means of time and separation.

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