We are going to make an Arduino control LED Piranha Plant :]

Step 1: What You'll Need

Arduino Uno
9 Resisters
9 LEDs - Red, Yellow, Orange is best since they need less amperage
PIR sensor
9v battery
arduino wall plug (you'll be cutting the connection so that you can connect it to the battery. 12v plug in will over heat the arduino)
LOTS of wire
Plant plot of your choice - plastic is easiest
8in styrofom ball
Large white pipe cleaner
Paint - green, red, white
paint brushes
PVC pipe
saw - to cut pvc pipe
hot glue gun
45 degree elbow pipes - 3
model magic - doesn't matter which color
foam core - for teeth
foam sheets

Step 2: Painting

After asembling the 3 45 degree elbow pipes, you'll want to put the model magic on it to coverthe rough parts. This takes about a day or so to dry. Then you can begin painting.
You'll want to paint everything first since it takes while to dry.

Plant pot, elbows, pvc pipe, and leaves will be green
Ball is red with white spots.
teeth - if you buy white foam core you wont have to worry about painting the teeth

You cut the leaf shape out of the foam sheet
you'll also want to cut a circle to fit the pot

After the ball is painted you need to cut out a mouth. Once the mouth is cut you'll nee to hallow out the inside. I used a knife to help cut mouth of it out. Then I used a spoon to refine it. Make sure you take about enough for the LED legs to come through.
Don't worry about painting the inside. You'll be cutting some foam core to fit inside. The mouth insert should be red

Step 3: Setting Up

Testing makes things perfect :]

PIR
GND -arduino GND
VCC - Arduino 5V
OUT - A0 / OnOff switch (refer to yellow gator clip)

ONOff switch
Green gator clip - 11
Yellow gator clip - arduino GND
Black gator clip - any capasitor
red gator clip - PIR ground

Step 4: Coding

int sensorPin = 0;    //Microphone Sensor Pin on analog 4
int sensorValue = 0;
int leds[] = {2,3,4,5,6,7,8,9,10}; // 9 total
int relay = 11;

void setup() {
pinMode(sensorPin, INPUT);
   pinMode(relay,OUTPUT);
   for(int i = 0;i<90;i++){
       pinMode(leds[i],OUTPUT);
   }
   Serial.begin(9600);
}

void loop() {
randomSequence();

// read the value from the sensor:
sensorValue = analogRead(sensorPin);
Serial.println(sensorValue);

if (sensorValue>950){ //The 'silence' sensor value is 509-511
    digitalWrite(relay,HIGH);
    delay(100);
} else {
    digitalWrite(relay,LOW);
}
}

// utterly random , a a kind of twinkling effect is acheived?
void randomSequence(){

int randomLed = random(0,9);
digitalWrite(leds[randomLed],HIGH);
      delay(50);

randomLed = random(0,9);
digitalWrite(leds[randomLed],LOW);

}

Step 5: Building Circuit Board

After testing and making sure everything works on the breadboard its time to move it all to the circuit board.

On the BACK on the circuit board, you'll want an EXPOSED wire touching all the capacitors to the "jumper" wire. Do this for both sides.

PIR
GND -arduino GND
VCC - Arduino 5V
OUT - A0 / OnOff switch (refer to yellow gator clip)

ONOff switch
Green gator clip - 11
Yellow gator clip - arduino GND
Black gator clip - any capasitor
red gator clip - PIR ground

LEDs
it doesn't matter with 2-10 you put the LED wire in

Step 6: Building It

Once the circuit board and the arduino are set up you'll want to connect it to the styrofoam ball. First you'll cut a hole in the back of the ball. Make sure to feed the wires through the pipe before you start soldering the LEDs to the ball. Once you're finished you can hot glue the ball to the pipe. Now we can hot glue the mouth insert, then teeth and lastly the pipe cleaner lips.

You'll also need to hot glue the leaves to the circular pot insert.

Inside of mouth DOESN'T need to be painted, it's covered by the mouth insert.

Step 7: Finishing Up

You'll need to cut a small hole into the plant pot for the sensor. If you haven't so already, you'll need to cut a small hole into the PVC pipe as well. This is so the wires can go through it.

When putting it together I sujest the way my image is.

I hope you enjoy the projects :]