markwilson.it

Last night I wrote a blog post about the “traffic lights” for my office. The trouble with the original setup was that the light was set to a particular state until I edited the code and uploaded a new version to the Arduino.

I was so excited about having something working that I hadn’t actually finished reading the Arduino Programming For Beginners: The Traffic Light Controller post that I referenced. Scroll down a bit further and James Bruce extends his traffic light sequence to simulate someone pressing a button to change the lights (e.g. to cross the road).

I worked on this to come up with something similar – using a variation on James’ wiring diagram (except with 2 LEDs rather than 3, and using pins 11 and 12 for my LEDs and 2 for the pushbutton switch), I now have a setup which waits for the button to be pressed, then sets the red LED, until the button is pressed again (when it goes green), etc.

My code is available on github but here’s the current version (just in case I lose that version as I get to grips with source control…):

/*
Red/green LED indicator with pushbutton control
Based on http://www.makeuseof.com/tag/arduino-traffic-light-controller/
*/

// Pins for coloured LEDs
int red = 11;
int green = 12;
int light = 0;

int button = 2; // Pushbutton on pin 2
int buttonValue = 0; // Button defaults to 0 (LOW)

void setup(){
// Set up pins with LEDs as output devices and switch for input
pinMode(red,OUTPUT);
pinMode(green,OUTPUT);
pinMode(button,INPUT);
}

void loop(){
// Read the value of the pushbutton switch
buttonValue = digitalRead(button);
if (buttonValue == HIGH){
changeLights();
delay(15000); // Wait 15 seconds before reading again
}
}

void changeLights(){
// Change the lights based on current value: 0 is not set; 1 is green; 2 is red
switch (light) {
case 1:
turnLightRed();
break;
case 2:
turnLightGreen();
break;
default:
turnLightRed();
}
}

void turnLightGreen(){
// Turn off the red and turn on the green
digitalWrite(red,LOW);
digitalWrite(green,HIGH);
light = 1;
}

void turnLightRed(){
// Turn off the green and turn on the red
digitalWrite(green,LOW);
digitalWrite(red,HIGH);
light = 2;
}

Now I’m wondering how long it will be before the kids work out that they too can change the status (like pushing the button at a pedestrian crossing!)…

It’s the school holidays, which means that working from home can be a little… noisy… at times.  Earlier today I saw a blog post from Scott Hanselman where he had hooked a light up to his instant messenger status to tell his family when he was on a call, or otherwise busy with work – and that gave me an idea…

Scott’s solution uses something called a Busylight but a) I’m too tight to spend €49 on this and b) the geek in me thinks “surely I can rig up something using a few LEDs?”. One of the comments on Scott’s post led me to an open source project called RealStatus but that uses an expensive USB HID for the LEDs so doesn’t really move me much further forward…

I decided that I should use my Arduino instead… with the added bonus that involving the children in the project might get them “onboard” too… the trouble is that my electronics prototyping skills are still fairly rudimentary.

As it happens, that’s not a problem – I found an Arduino traffic light program for beginners and, as I don’t have a yellow LED right now, I adapted it to what I do have – simple red/green status (my son and I had fun trying different resistors to adjust the brightness of the LEDs)

You can see the breadboard view here (generated with Fritzing – I’m still working out how to make this into a schematic) and below is my Arduino code (which is also available on github – although I might have worked on it a bit by the time you read this):

// Pins for coloured LEDs
int red = 12;
int green = 13;

void setup(){
// Set up pins as output devices
pinMode(red,OUTPUT);
pinMode(green,OUTPUT);
}

void loop(){
// Change the lights
// turnLightRed();
turnLightGreen();
}

void turnLightGreen(){
// Turn off the red and turn on the green
digitalWrite(red,LOW);
digitalWrite(green,HIGH);
}

void turnLightRed(){
// Turn off the green and turn on the red
digitalWrite(green,LOW);
digitalWrite(red,HIGH);
}

It’s pretty simple really – I just call the turnLightRed() or turnLightGreen() function according to whether I am ready to accept visitors. In itself, that’s a bit limited but the next step will be to work out how to send commands to the Arduino over USB (for some integration with my instant messaging client, perhaps) or even using a messaging service (Twitter?) and some network connectivity… more research required!