I'm using an Arduino MEGA for all of the following examples. In the Tools menus of the Arduino IDE, I have the following settings:

• Board: Arduino Mega or Mega 2560
• Processor: ATmega1280
• Port: COM3 (this property can be determined in the device manager)

It's important to note these settings are for my specific device and the above list is for my own reference mostly. Your device may differ in all three settings!

I guess this is probably a lot of people's first project with an Arduino. It was very simple, although I did have to look up a tutorial to see how to do it using a breadboard, which can be found here. Here's the code using the Arduino software.

int ledPin = 53;

void setup() {
  // put your setup code here, to run once:
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(ledPin, HIGH); 
  delay(3000);
  digitalWrite(ledPin, LOW);
  delay(3000);
}

As for the actual wiring, I had a ground coming from the Arduino's digital ground to the breadboard ground, and then another wire coming from pin 53 to row 10 on my breadboard... from there it went through a 290 ohm resistor which stretched to row 5 next to the short end of an LED. The long end of the LED ended back into the ground of the breadboard and subsequently into the Arduino itself. A pretty simple circuit.

Click here to download both the arduino source code and the C# code (Visual Studio Express 2010)

The next thing I wanted to do was be able to turn the LED light on and off by clicking a button. To do this, I found a tutorial here (may want to translate that page) that helped me bridge the gap between the Arduino and C#. From there I altered the C# code slightly and boom! There it was! I also bought more LED lights and ran 3 of them in parallel... just to prove to myself I knew what I was doing (at least a little... lol).

All this setup is doing is using a C# program that uses serialPort.Write to send a value of either "1" (on) or "0" (off). The arduino program (which obviously needs to be uploaded to the Arduino itself) uses a function called Serial.read() to assign a value to a char variable, then the program goes through a switch/case and executes commands depending on if the value is 1 or 0. Pretty freakin' simple.