Traffic Light LED Module

Large LEDs with built-in current limiting resistors.

DESCRIPTION

The Traffic Light LED Module has large Red, Yellow and Green LEDs arranged in a standard traffic light pattern with built-in current limiting resistors.

PACKAGE INCLUDES:

• Traffic Light LED Module

KEY FEATURES OF TRAFFIC LIGHT LED MODULE:

• Large 8mm Red, Yellow and Green LEDs
• LEDs active HIGH
• Built-in current limiting resistors
• 3.3 and 5V compatible

This module includes large 8mm Red, Yellow and Green LEDs arranged like a typical traffic light that are useful for experimenting with traffic signals, using them on a railroad model or as some type of good/caution/bad status indicators for a project.

The modules have current limiting resistors built-in, so they can be connected directly to the pins of an MCU.  You can even plug it directly into the female header of most Arduino boards where you have 3 digital pins next to a ground, such as using the Uno pins 11, 12, 13 & Gnd.  The LEDs are lit when a logic HIGH is applied to the pins.

Module Connections

1×4 Header

• G = Green LED, active HIGH
• Y = Yellow LED, active HIGH
• R = Red LED, active HIGH
• GND = Ground

OUR EVALUATION RESULTS:

It is pretty common to do a traffic light setup at some point, even if it is just to play with the software logic of it all.  These help take those efforts to the next level and are useful for general indicators such as coupling with the soil moisture sensor to show the status of the plant soil moisture.

The program below uses two of the modules to implement a typical 2-way traffic light.  It uses a simple state machine to control the LEDs.  The state machine is incremented by monitoring the elapsed time using the millis() function. This allows the microcontroller to be off doing other things when it is not busy updating the lights.

The state machine is set to increment every 2 seconds and calls the UpdateLights function each time it increments.  The Switch Case statement only takes action on states 0,4,5 and 9.  The other states are ignored so the last state remains in effect.  This allows us to set the delay between the different states.  A Green and Red light cycles take 4 states (8 seconds), while the Yellow light cycle only lasts 1 state (2 seconds).

You can hook up the LEDs to any 6 digital pins, we use 4-9 in our example here.

Traffic Light LED Module Example Program

/*
This program operates two of the traffic signal modules to simulate 
an intersection on a road.
*/
const int RED1_PIN = 4;     // select digital pins for 1st light LEDs
const int YELLOW1_PIN = 5;
const int GREEN1_PIN = 6;
const int RED2_PIN = 7;     // select digital pins for 2nd light LEDs
const int YELLOW2_PIN = 8;
const int GREEN2_PIN = 9;
const int ON = HIGH;        // Remapping High/Low to On/Off to better match LED state 
const int OFF = LOW;
const unsigned long period = 2000;   //Number of milliseconds between state changes (2 secs)
unsigned long lastMillis;           // Our last milli reading
unsigned long currentMillis;        // Our current milli reading

int state = 0;                      // State machine ticker, goes 0-9 and then cycles back to 0
//===============================================================================
//  Initialization
//===============================================================================
void setup() 
{ 
  pinMode (RED1_PIN, OUTPUT);     // Define our LED pins as outputs
  pinMode (YELLOW1_PIN, OUTPUT);
  pinMode (GREEN1_PIN, OUTPUT);
  pinMode (RED2_PIN, OUTPUT);
  pinMode (YELLOW2_PIN, OUTPUT);
  pinMode (GREEN2_PIN, OUTPUT);
  lastMillis = millis();        // Capture initial start time
}
//===============================================================================
//  Main
//===============================================================================
void loop() 
{
  currentMillis = millis();                     // Get current time in millis
  if (currentMillis - lastMillis >= period) {   // Time to switch state
      UpdateLights();                           // Call UpdateLights to handle new state
      lastMillis = currentMillis;               // Restart the milli counter
      state++;                                  // Increment state
      if (state > 9) state = 0;                 // Handle any roll-over
  }
}

void UpdateLights()
{
  switch (state){
    case 0:   // Lane 1 has right of way.
        digitalWrite(GREEN1_PIN, ON);
        digitalWrite(YELLOW2_PIN, OFF); 
        digitalWrite(RED2_PIN, ON);
        digitalWrite(RED1_PIN, OFF);
      break;  
    case 4:   // Lane 1 goes yellow
        digitalWrite(GREEN1_PIN, OFF);
        digitalWrite(YELLOW1_PIN, ON);
      break;
    case 5:   // Lane 2 has right of way
        digitalWrite(GREEN2_PIN, ON);
        digitalWrite(RED2_PIN, OFF);
        digitalWrite(YELLOW1_PIN, OFF);
        digitalWrite(RED1_PIN, ON);
        break;
    case 9:   // Lane 2 goes yellow
        digitalWrite(GREEN2_PIN, OFF);
        digitalWrite(YELLOW2_PIN, ON); 
        break;
  }
}

BEFORE THEY ARE SHIPPED, THESE MODULES ARE:

• Sample inspected for correct components and tested per incoming shipment.

Notes: 

1. None

TECHNICAL SPECIFICATIONS