Yes, it doesn't need relays. The parts required are:
2 transistors (pins 13 and 8 with this code)
1 motion sensor (data input on pin 2), this one: PIR (motion) sensor : ID 189 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits
optional- 1 powerswitchtail (to turn the speakers off when not in use, on pin 0)
I've found that the mp3 player needs to be recharged once a week. The wires to the battery are usable, so I'm looking at cutting into those and powering it off the arduino. I'll update later.
I've cleaned up the code, removed some old junk from it, and added some more comments to make it easier for a beginner to read.
// when I walk in the house a motion sensor is activated.
//The arduino turns on the speakers with a powerswitchtail. Then
// it activates the mp3 player. After playing the song for 1
// minute, the speakers are turned off. Then the song is forwarded
// to the next one, and the mp3 player is turned off.
//A song will play every other time so that it doesn't play
// on exit, only entry.
int speaker = 0; //powerswitchtail for speakers
int Forward = 13; // song forward
int Play = 8; // play/pause a song
int motion = 1;
int entry=0;
void setup() {
//Serial.begin(9600);
pinMode(Forward, OUTPUT); //to a transistor
pinMode(Play, OUTPUT); //to a transistor
pinMode(0,OUTPUT); //speaker
pinMode(2,INPUT); //motion sensor input
digitalWrite(speaker,LOW); //speakers off
}
void loop()
{
motion=digitalRead(2); // read motion sensor on pin 2
if(motion==1){ // if the motion sensor has been activated
if(entry==1){ // entry goes from 0 to 1 and 1 to 0 every time that
// the motion sensor is activated. It will only
// play a song every other time, when it's 1
//TURN the MP3 player ON by pressing 'play' for 3 seconds
digitalWrite(Play, HIGH);
delay(3500);
digitalWrite(Play, LOW);
delay(5260); //wait for the mp3 to come on
// TURN SPEAKERS ON
digitalWrite(speaker,HIGH);
//PLAY SONG
delay(60000); //wait 1 minute while the song plays
// TURN SPEAKERS OFF
digitalWrite(speaker,LOW);
//GO FORWARD ONE SONG
digitalWrite(Forward, HIGH); //pass the current song
delay(145);
digitalWrite(Forward, LOW);
delay(300); // let it load in
//TURN mp3 player OFF by pressing 'play' for 3 seconds
digitalWrite(Play, HIGH);
delay(3500);
digitalWrite(Play, LOW);
delay(4000);
entry=0; // make 'entry' 0 so that next time it won't play a song
} else{
entry=1; // else, next time play the song
delay(20000); //waits 20 seconds for the person to leave the house
}//end entry if statement
} //END MOTION SENSOR IF STATEMENT
delay(100);
} // END MAIN LOOP