Traffic Signal

My Lego City is moving now! We are going to need more than a stop sign to keep the traffic in order. Let’s build a traffic light!

Goal:

– Build a traffic signal that sequences through the traffic lights.

Challenges:

– Construct the traffic signal.

– Multiple LED circuit.

• Code the sequence.

Components:

• Raspberry Pi (or any NodeJS host)
• Arduino (I used the Mega 2560 but any will do)
• 1.8v LEDs
• breadboard
• 220 Ohm resistors

Schematic:

Code:

We will need to initialize the board as usual and then define the three LED pins for our lights. Because I’m using British style signaling (or close enough), there will be a yellow light before and after the red and green lights. This is handy because you could easily connect the alternate red/green color and have both signals (6 lights) using three pins.

Basic Flow

• Red – Green – 6 seconds
• Yellow – Yellow – 2 seconds
• Green – Red – 6 seconds
• Yellow – Yellow – 2 seconds
• Loop

The setTimeout() function is something we will use often  because it allows us to delay an action. It consists of two basic parameters, the callback function and thedelay in milliseconds.

Filename

trafficsignal.js

 //trafficsignal.js var five = require("johnny-five"); var board = new five.Board(); //Arduino board  connection board.on("ready", function() { // Traffic Signal LEDs var trafficSignalLedRG = new  five.Led(49); //Signal Red & Green var trafficSignalLedY = new five.Led(50); //Signal Yellow var  trafficSignalLedGR = new five.Led(51); //Signal Green & Red var trafficSignalState = 0; // Initialize  Signal State function trafficSignal(){ if (trafficSignalState == 0){ // Red Green  console.log("traffic crossing RG"); trafficSignalLedRG.on(); trafficSignalLedY.off();  trafficSignalLedGR.off(); trafficSignalState = 1; setTimeout(trafficSignal,6000); } else if  (trafficSignalState == 1){ // Yellow Yellow console.log("traffic crossing Y");  trafficSignalLedRG.off(); trafficSignalLedY.on(); trafficSignalLedGR.off(); trafficSignalState = 2;  setTimeout(trafficSignal,2000); } else if (trafficSignalState == 2){ // Green Red  console.log("traffic crossing GR"); trafficSignalLedRG.off(); trafficSignalLedY.off();  trafficSignalLedGR.on(); trafficSignalState = 3; setTimeout(trafficSignal,6000); } else if  (trafficSignalState == 3){ // Yellow Yellow console.log("traffic crossing Y");  trafficSignalLedRG.off(); trafficSignalLedY.on(); trafficSignalLedGR.off(); trafficSignalState = 0;  setTimeout(trafficSignal,2000); } } trafficSignal(); // Start Traffic Signal });

Now save and close your file.

npm init

npm install johnny-five --save

node trafficsignal.js

root@thethingbox:~/IoL# node trafficsignal.js 
1442332839007 Device(s) /dev/ttyACM0 
1442332839092 Connected /dev/ttyACM0 
1442332842044 Repl Initialized 
>> traffic crossing RG
traffic crossing Y
traffic crossing GR
traffic crossing Y
traffic crossing RG