Since there's very little room in the helmet the wireless system was powered by a single 7.4V NiMH battery pack. The digital servos used in the helmet are designed to be operated on 7.4V so a DC/DC converter is used to provide power for the Arduino, XBee and LEDs. 

A larger image is available here.

Here's the code for the helmet-

#include "Servo.h" // include the servo library

Servo faceplateServo;
Servo chinServo;

int ledPin1 = 4;                    // control pin for LED eyes
int servoPin1 = 2;               // control pin for face plate servo
int servoPin2 = 3;              // control pin for chin

void setup() {

faceplateServo.attach(servoPin1);         // attaches the servo on pin 2 to the servo object
chinServo.attach(servoPin2);                // attaches the servo on pin 3 to the servo object
faceplateServo.write(30);                      // rotate face plate servo to 30 degrees
chinServo.write(95);                               // rotate chin servo to 95 degrees
pinMode(ledPin1, OUTPUT);                 // sets the LED pin as output
digitalWrite(ledPin1, HIGH);                   // turn on LED eyes

Serial.begin(9600);
}

void loop() {


// look for a capital A over the serial port and turn off LED
if (Serial.available() > 0) {
if (Serial.read() == 'A') {
digitalWrite(ledPin1, LOW);                         // turn off LED eyes
delay(500);                                                  // wait half a second
faceplateServo.write(95);                           // rotate the face plate servo to 95 degrees
chinServo.write(20);                                    // rotate the chin servo to 20 degrees
delay(4000);                                                // wait 4 seconds
chinServo.write(95);                                    // rotate the chin servo to 95 degrees
faceplateServo.write(30);                           // rotate the face plate servo to 30 degrees
digitalWrite(ledPin1, HIGH);                        // turn on LED eyes

}
}
}