RFID Controlled Car Trunk

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Step 5: Understanding the Code

Picture of Understanding the Code
Thanks to an unknown code writer for most of this code!
#include <Servo.h>  // Includes libraries (computer files) that include lines of code for the servo
Servo myservo; // Gives the servo a name

int RFIDResetPin = 0;

//Register your RFID tags here
char tag1[13] = "------------";  //First tag ID, I replaced the letters and numbers with a corresponding amount of dashes (i'd rather you              
                                                  //not hack my system...)

char tag2[13] = "------------";  //Second tag ID

void setup(){                        // everything within the void setup runs the code once on start-up 
  Serial.begin(9600);    //Sets up a connection to the computer when prototyping, incredibly useful to figure out whats happening in                      
                                        //the code because it can print lines of code onto a computer screen 
  myservo.attach(8);     //Attaches the servo to a specific pin on the arduino, this is like the lane of a highway for information 
  myservo.write(178);  // Sets the limited rotation (0-180 degrees) servo to 178, the idle position
  pinMode(RFIDResetPin, OUTPUT);  //Clears the slate for sensing a tag
  digitalWrite(RFIDResetPin, HIGH);    //puts it on "high alert"


void loop(){              //everything within the void loop is run through in a linear fashion over and over again 
  char tagString[0];                    //the next couple of lines work with the incoming data to turn it into numbers and letters which form
  int index = 0;                            //the ID tag 
  boolean reading = false;

  while(Serial.available()){               //while there is a serial connection (while the reader is communicating to the board...)

    int readByte =; //read next available byte          //code that begins decoding (haha) the binary 

    if(readByte == 2) reading = true; //begining of tag
    if(readByte == 3) reading = false; //end of tag

    if(reading && readByte != 2 && readByte != 10 && readByte != 13){
      //store the tag
      tagString[index] = readByte;
      index ++;

  checkTag(tagString); //Check if it is a match
  clearTag(tagString); //Clear the char of all value
  resetReader(); //reset the RFID reader

void checkTag(char tag[]){                   //Check the read tag against known tags

  if(strlen(tag) == 0) return; //empty, no need to contunue

  if(compareTag(tag, tag1)){                 // if matched tag1, do this
    servoGo();                                            //Activate the servo!
    Serial.println("card 1 read");             //print "card 1 read" to the computer, helps see if the code reaches this point when and how it
  else if(compareTag(tag, tag2)){           //if matched tag2, do this
   servoGo();                                                //Activate the servo!
   Serial.println("card 2 read");
/* else{
    Serial.println(tag); //read out any unknown tag
    Serial.println("unknown card");


void servoGo(){                                     
  Serial.println("Servo Activated");         //prints a line to the computer that tells me that its reaches this point 
    myservo.write(20);                               //writes the servo to a position that will pull the cord that pops the trunk
    myservo.write(178);                            //resets the position for the next activation 
  Serial.println("Servo Action Complete");    //prints a line to the computer confirming the completion of this method (external code of

/////////////////////////////////// The rest is code used to control the system that reads the code

void resetReader(){

//Reset the RFID reader to read again.

  digitalWrite(RFIDResetPin, LOW);
  digitalWrite(RFIDResetPin, HIGH);

void clearTag(char one[]){

//clear the char array by filling with null - ASCII 0
//Will think same tag has been read otherwise

  for(int i = 0; i < strlen(one); i++){
    one[i] = 0;

boolean compareTag(char one[], char two[]){

//compare two value to see if same,
//strcmp not working 100% so we do this

  if(strlen(one) == 0) return false; //empty

  for(int i = 0; i < 12; i++){
    if(one[i] != two[i]) return false;

  return true; //no mismatches

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Great place to start. I can see where it could be integrated into the car a little more. One could use the car's own battery, make sure your Arduino can take 14 volts or use a regulator. Most cars now have an electric trunk release so you could hook into that using a relay instead of the servo.
Heat sinks, good idea, I rarely use one though. I would recommend anyone new to soldering use one. I find if you move quickly you get the best joints. If your flux is smoking get the joint completed before it quits and don't be afraid to use lots.