Escape-Room Prop · 2017–2019

Briefcase Bomb Prop

Tactical Escape 101 · Lead Prop Engineer

A prop built to look like a briefcase bomb that customers race to "defuse" before the timer runs out — flip the colored switches in order, turn every key, seat the audio cables, enter the passkey, then cut the right wire. Get it wrong and the clock speeds up 10× into a heartbeat finale.

ArduinoC4 coordinated MCUs 7-segment timerKeypad + LCDPhotoresistor trigger
Download Arduino source Back to portfolio
How it works

Design & Build

From a hand-cut proof of concept to a store model that survived 300+ groups, the prop grew into a multi-board system wired around a master "timer" Arduino.

Initial design

The first build was a proof of concept for the owners of Tactical Escape 101. To finish the challenge the colored switches had to be flipped in the correct order, every key inserted and turned, every cable seated, and the right passkey entered — with a final wire to cut. Each completed objective lit a green indicator. Finish everything and cut the correct wire and the timer stops to a victory tune; cut the wrong one and it accelerates 10× into a heartbeat animation that slowly flatlines.

First briefcase prop design
The first prototype — proof of concept that earned a bigger budget. The timer was too small, the hand-cut board looked unprofessional, and there was no sound.

Store model

After improvements and testing, this model was approved and a room was designed around it. The photo below was taken after more than 300 uses — the case shows wear but the functionality held. A larger, easier-to-read 7-segment timer replaced the 50¢ display, and two cuttable wires were added at the top for a stronger finish (a $10, 100-ft roll of red wire lasts about two months). The exterior is screwed shut so players can't reach inside and pull the wiring.

Final store model of the briefcase prop
The approved store model after 300+ runs.

Internally, each switch ties to 5 V, ground, and a pin on the switches Arduino; when flipped in the right order it lights the green indicator and signals the master timer board. Every sub-board reports into timer, which only stops the clock once it has received all the correct signals and the right wire is cut. A top-mounted photoresistor starts the countdown the moment the case is opened to room light. The six audio jacks run on a variable voltage — the cable loops induce enough of a field to interfere with the circuits, so each jack is driven and read on a changing signal to tell the locations apart. A keypad + LCD handles a configurable passkey. Total parts cost came in around $200 including spares.

Wiring analysis of the briefcase prop
Wiring breakdown — switches, audio plugs, keypad and the master timer board.

Circuit diagram

The full circuit, drawn in Fritzing.

Full Fritzing circuit diagram
Complete wiring diagram created in Fritzing.
Firmware

The Code

Four Arduinos split the work: a master countdown timer, the colored switches, the audio plugs & keys, and a keypad lock. Expand any listing to read the source.

timer.ino 
/*
Lucas Dahl
60 minute countdown for 4 digit 7 segment led display
Used for the suitcase bomb design, also uses code for the 7 digit code also on github
The output pins for the other arduinos will go into A1, safe, death, A5, and A3
*/
#include <TimerOne.h>


int sensorPin = A1;
int musicer = A0;
int sensorValue = 0;  // variable to store the value coming from the sensor
int resistorValue = 0;
int starter =0 ;
int safe = A2;
int death = A4;

// pins for the 4 digit 7 segment led, these can change depending on which is orders so look at the data sheet for the led.
int a = 2;
int b = 3;
int c = 4;
int d = 5;
int e = 6;
int f = 7;
int g = 8;
int p = 9;
int d4 = 10;
int d3 = 11;
int d2 = 12;
int d1 = 13;

// n is the number that is displayed, the countdown function is on the bottom but if you wanted a different countdown then 60 min then change this value.
long n = 5959;
int x = 100;
//Used to change the speed of the coundown, if you add more programs to this code the countdown will be slower.
int timing_adjust = 5;

//A larger adjust for speed, if this is changed to 0 then it will count down 10 times faster. use this as a punishment for doing something wrong
int count = 9;

int minute = 0;
int stopper = 0;

//flip is the flipswitches part of the suitcase bomb, pass is the 7 digit passkey, and plug is the audio plug part.
int flip = 0;
int pass = 0;
int plug = 0;

// variable to change the count
int change_count = 9;

//the two pins that connect to the wire that needs to be cut, one stops the time and the other increases the speed.
int readDeath = 0;
int readSafe = 0;

int nostop = 0;
int toners = 0;
int ending = 0;

void setup()
{
  Serial.begin(9600);

  pinMode(d1, OUTPUT);
  pinMode(d2, OUTPUT);
  pinMode(d3, OUTPUT);
  pinMode(d4, OUTPUT);
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
  pinMode(p, OUTPUT);
  pinMode(musicer, OUTPUT);

  Timer1.initialize(100000);
  Timer1.attachInterrupt( countdown );
}
/***************************************/
void loop()
{
  //The timer will only start when the starter changes, this is so that when the bomb opens up the photoresistor will detect the light and start the bomb
  if (starter ==0)
  {
    delay(1000);
    sensorValue = analogRead(sensorPin);
    if (sensorValue > 40)
     {
        starter = 1;
     }
  }
  flip = analogRead(A5);
  readDeath = analogRead(death);
  pass = analogRead(A3);
  readSafe = analogRead(safe);
  if (readDeath < 800)
  {
   change_count = 1;
   nostop = 1;
  }

  //baseling for the inputs for the other arduinos
  if (flip > 900 && pass > 800)
  {
    if (readDeath < 800)
    {
       change_count = 1;
       if (readSafe <900 && n == 0001)
       {
        n = 1;
        stopper = 1;
        if (toners == 0){
        winner();
        toners = 1;
       }

       }
    }
    //The time will stop only when the conditions are set from the other arduios and then the wire is cut
    if(nostop == 0)
    {
      if (readSafe < 900 )
      {
        stopper = 1;
        if (toners == 0){
        winner();
        toners = 1;
        }
      }
    }
  }
  //If the conditions are not set and the time runs out they lose
  if(starter == 1 && n == 0 && toners == 0)
  {
   loser();
   toners = 1;
  }
  //when the timer counts down at the 30min 15min marks it will play a tune to alert them
  if(n == 3000)
  {
    tone(musicer, 1000);
    delay(1000);
    noTone(musicer);
  }
   if(n == 1500)
  {
    tone(musicer, 1000);
    delay(1000);
    noTone(musicer);
  }
  //at the last 5 seconds it will beep and then play a heart beat animation and tune
   if(n == 5 && ending == 0)
  {
    tone(musicer, 1000);
    delay(10);
    noTone(musicer);
    ending = 1;
  }
   if(n == 4 && ending == 1)
  {
    tone(musicer, 1000);
    delay(10);
    noTone(musicer);
    ending = 2;
  }
   if(n == 3 && ending == 2)
  {
    tone(musicer, 1000);
    delay(10);
    noTone(musicer);
    ending = 3;
  }
   if(n == 2 && ending == 3)
  {
    tone(musicer, 1000);
    delay(10);
    noTone(musicer);
    ending = 0;
  }

 //This loops through the different digits and displays them by using a modulus fuction to specifiy the digit
  clearLEDs();//clear the leds
  digits(0);//turns on the first digit
  numbers((n/1000));// get the value of first digit
  delay(timing_adjust);//delay 5ms

  clearLEDs();//clear leds
  digits(1);//Light up second digit
  numbers((n%1000)/100);// get the value of second digit using modulus
  delay(timing_adjust);//delay 5ms

  clearLEDs();//clear the leds
  digits(2);//Light up third digit
  numbers(n%100/10);//get the 3rd digit
  delay(timing_adjust);//delay 5ms

  clearLEDs();//clear the leds
  digits(3);//Light up fourth digit
  numbers(n%10);//Get the value of fourth digit
  delay(timing_adjust);//delay 5ms
}
/**************************************/
void digits(int x) //light up a 7-segment display
{
  //The 7-segment LED display is a common-cathode one. So also use digitalWrite to  set d1 as high and the LED will go out
  digitalWrite(d1, HIGH);
  digitalWrite(d2, HIGH);
  digitalWrite(d3, HIGH);
  digitalWrite(d4, HIGH);

  switch(x)
  {
    case 0:
    digitalWrite(d1, LOW);//Light digit one
    break;
    case 1:
    digitalWrite(d2, LOW); //Light digit two
    digitalWrite(p, HIGH);
    break;
    case 2:
    digitalWrite(d3, LOW); //Light digit three
    break;
    default:
    digitalWrite(d4, LOW); //Light digit four
    break;
  }
}
//Simplifies the digit leds that need to be powered by setting leds to a given number
void numbers(int x)
{
  switch(x)
  {
    default:
    zero();
    break;
    case 1:
    one();
    break;
    case 2:
    two();
    break;
    case 3:
    three();
    break;
    case 4:
    four();
    break;
    case 5:
    five();
    break;
    case 6:
    six();
    break;
    case 7:
    seven();
    break;
    case 8:
    eight();
    break;
    case 9:
    nine();
    break;
  }
}
void clearLEDs() //clear the 7-segment display screen
{
  digitalWrite(a, LOW);
  digitalWrite(b, LOW);
  digitalWrite(c, LOW);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
  digitalWrite(p, LOW);
}

void zero() //the 7-segment led display 0
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, HIGH);
  digitalWrite(g, LOW);
}

void one() //the 7-segment led display 1
{
  digitalWrite(a, LOW);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void two() //the 7-segment led display 2
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, LOW);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, LOW);
  digitalWrite(g, HIGH);
}
void three() //the 7-segment led display 3
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, HIGH);
}

void four() //the 7-segment led display 4
{
  digitalWrite(a, LOW);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);
}

void five() //the 7-segment led display 5
{
  digitalWrite(a, HIGH);
  digitalWrite(b, LOW);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, LOW);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);
}

void six() //the 7-segment led display 6
{
  digitalWrite(a, HIGH);
  digitalWrite(b, LOW);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);
}

void seven() //the 7-segment led display 7
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);
}

void eight() //the 7-segment led display 8
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);
}

void nine() //the 7-segment led display 9
{
  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, LOW);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);
}
/*******************************************/
void countdown()
{
//This is the function that controls the countdown, it subtracts from the countdown, and then when it reaches 60 it subtracts 40 to make it on a clock system of counting.
  if(starter == 1 && stopper == 0){
    count --;
  if(count == 0)
  {
    minute++;
    count = change_count;
    n--;
    if(minute == 60)
    {
      n = n-40;
      minute = 0;
    }
    if(n == 0)
    {
      n = 0000;
    }
  }
  }
}
void winner()
{
   tone(musicer, 523);
  delay (100);
  noTone(musicer);
  delay(25);
  tone(musicer, 659);
  delay (125);
  noTone(musicer);
  delay(25);
  tone(musicer, 680);
  delay (150);
  noTone(musicer);
  delay(25);
  tone(musicer, 659);
  delay (125);
  noTone(musicer);
  delay(50);
  tone(musicer, 1000);
  delay (175);
  tone(musicer, 1200);
  delay (250);
  noTone(musicer);

}
void loser()
{
  tone(musicer, 100);
  delay (100);
  noTone(musicer);
  delay(50);
  tone(musicer, 200);
  delay (50);
  noTone(musicer);
  delay(250);
   tone(musicer, 100);
  delay (100);
  noTone(musicer);
  delay(50);
  tone(musicer, 200);
  delay (50);
  noTone(musicer);
  delay(450);
    tone(musicer, 100);
  delay (100);
  noTone(musicer);
  delay(50);
  tone(musicer, 200);
  delay (50);
  noTone(musicer);
  delay(700);
  tone(musicer, 100);
  delay (100);
  noTone(musicer);
  delay(50);
  tone(musicer, 200);
  delay (50);
  noTone(musicer);
  delay(1000);
  tone(musicer, 100);
  delay (100);
  noTone(musicer);
  delay(50);
  tone(musicer, 200);
  delay (50);
  noTone(musicer);
  delay(1200);
  tone(musicer, 1000);
  delay(1000);
  noTone(musicer);
}
switches.ino 
/*
Lucas Dahl
Key switechs part of the breifcase bomb prop
 */

     // the color switcches
const int redSwitch = 5;
const int blueSwitch = 3;
const int greenSwitch = 4;
const int yellowSwitch = 6;
const int purpleSwitch = 7;
const int ledPin = 13;
const int redline = 1;
const int blueline = 2;
int pass = 0;

// variables will change:
int blueState = 0;
int redState = 0;
int greenState = 0;
int yellowState = 0;
int purpleState = 0;

void setup() {
  pinMode(redSwitch, INPUT);
  pinMode(yellowSwitch, INPUT);
  pinMode(greenSwitch, INPUT);
  pinMode(blueSwitch, INPUT);
  pinMode(purpleSwitch, INPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(10, INPUT);
  Serial.begin(9600);
}

void loop(){
  // read the state of the pushbutton value:
  Serial.println(blueState);
  blueState = digitalRead(blueSwitch);
  greenState = digitalRead(greenSwitch);
  purpleState = digitalRead(purpleSwitch);
  yellowState = digitalRead(yellowSwitch);
  redState = digitalRead(redSwitch);
  pass = digitalRead(10);
//If the blue purple and red ones are on tand the others are off then it sends a high output signal
  if (blueState == HIGH && purpleState == HIGH && redState == HIGH ) {
   if(greenState == LOW && yellowState == LOW){
    delay(3000);
    digitalWrite(ledPin, HIGH);
    if (pass == HIGH)
    {
    digitalWrite(11, HIGH);
    }
    else
    {
     digitalWrite(11, LOW);
    }
  }

  else {
    digitalWrite(11, LOW);
  }
  }
}
audio_plugs_and_keys.ino 
/*
Lucas Dahl
Audio Plugs and keys Arduino
 */

//The Audio cords create large loops that take on a lot of interference so there are ouput voltages that changee and then it reads the signal to minimize noise
int sensorcenter = A4;
int sensortop = A5;
int sensorbottom = A3;
int sensorswitch = A2;
int outbottom = 2;
int outcenter = 3;
int outtop = 4;
int outswitch = 5;
int sensorValuec = 0;
int sensorValueb = 0;
int sensorValues = 0;
int sensorValuet = 0;
int ledPin = 13;

int cent = 0;
int bot = 0;
int top = 0;
int swit = 0;

void setup() {
  pinMode(outbottom, OUTPUT);
  pinMode(outcenter, OUTPUT);
  pinMode(outtop, OUTPUT);
  pinMode(outswitch, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(7, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  // read the value from the sensor:
  digitalWrite(outcenter, HIGH);
  sensorValuec = analogRead(sensorcenter);
  if( sensorValuec > 1000)
  {
   cent = 1;
  }
  else
  {
   cent = 0;
  }
  digitalWrite(outcenter, LOW);

  digitalWrite(outbottom, HIGH);
  sensorValueb = analogRead(sensorbottom);
  //Serial.println(sensorValueb);
  if( sensorValueb > 1000)
  {
   bot = 1;
  }
  else
  {
   bot = 0;
  }
  digitalWrite(outbottom, LOW);


  digitalWrite(outswitch, HIGH);
  sensorValues = analogRead(sensorswitch);
  Serial.println(sensorValues);
  if( sensorValues > 1000)
  {
   swit = 1;
   digitalWrite(12, HIGH);

  }
  else
  {
    digitalWrite(12, LOW );

   swit = 0;
  }
  digitalWrite(outswitch, LOW);

  digitalWrite(outtop, HIGH);
  sensorValuet = analogRead(sensortop);
  Serial.println(sensorValuet);
  if( sensorValuet > 1000)
  {
   top = 1;
  }
  else
  {
   top = 0;
  }
  digitalWrite(outtop, LOW);
  digitalWrite(outbottom, LOW);
  digitalWrite(outcenter, LOW);

  if(top == 1 && bot ==1 && cent ==1)
  {
  digitalWrite(ledPin, HIGH);
  delay(100);
  if(swit ==1)
  {
   digitalWrite(7, HIGH);
  }
  else{
    digitalWrite(7, LOW);
    delay(1000);
  }
  }
 else
{
 //Serial.println(top);

  digitalWrite(ledPin, LOW);
  delay(100);

}

}
keypad.ino 
#include "Keypad.h"
#include "LiquidCrystal.h"
#include "EEPROM.h"

//May have to change the lcd libraries depending on the lcd screen used
LiquidCrystal lcd(9,8,7,6,5,4);

//The typed password, the stored and the changed password variables
char password[7];
char pass[7],pass1[7];
int i=0;
char customKey=0;
//The keypad matrix can be changed as well depending on the keypad used
const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
char hexaKeys[ROWS][COLS] = {
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};
byte rowPins[ROWS] = {A0,A1,A2,A3}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {A4,A5,3,2};   //connect to the column pinouts of the keypad
//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);

//pins for the buzzer and the output which can go to the relay
int buzzer = 10;
int output = 13;

void setup()
{
  Serial.begin(9600);

  lcd.begin(16,2);
  pinMode(output, OUTPUT);
  pinMode(buzzer, OUTPUT);

  lcd.print(" Electronic ");
  lcd.setCursor(0,1);
  lcd.print(" BOMB Lock ");
  delay(1000);
  lcd.clear();
  lcd.print("Enter Passkey:");
  lcd.setCursor(0,1);
  for(int j=0;j<7;j++)
    EEPROM.write(j, j+49);
  for(int j=0;j<7;j++)
    pass[j]=EEPROM.read(j);
}

void loop()
{
  digitalWrite(output, HIGH);
  customKey = customKeypad.getKey();
  if(customKey=='#')
    change();
  if (customKey)
  {
    password[i++]=customKey;
    lcd.print(customKey);
    Serial.print(customKey);
  }
  if(i==7)
  {
    delay(200);
    for(int j=0;j<7;j++)
      pass[j]=EEPROM.read(j);
      //strncmp is a string comparison, its a nice tool for passkey checks
    if(!(strncmp(password, pass,7)))
    {

      digitalWrite(output, HIGH);
      //beep();
      lcd.clear();
      lcd.print("Passkey Accepted");
      digitalWrite(output, LOW);
      delay(2000);
    }
    else
    {
      digitalWrite(output, HIGH);
      digitalWrite(buzzer, HIGH);
      lcd.clear();
      lcd.print("Access Denied...");
      lcd.setCursor(0,1);
      delay(2000);
      lcd.clear();
      lcd.print("Enter Passkey:");
      lcd.setCursor(0,1);
      i=0;
      digitalWrite(buzzer, LOW);
    }
  }
}
void change()
{
  int j=0;
  lcd.clear();
  lcd.print("Current Password");
  lcd.setCursor(0,1);
  while(j<7)
  {
    char key=customKeypad.getKey();
    if(key)
    {
      pass1[j++]=key;
      lcd.print(key);
      beep();
    }
    key=0;
  }
  delay(500);
  if((strncmp(pass1, pass, 7)))
  {
    lcd.clear();
    lcd.print("Wrong Passkey...");
    lcd.setCursor(0,1);
    lcd.print("Better Luck Again");
    delay(1000);
  }
  else
  {
    j=0;
    lcd.clear();
    lcd.print("Enter New Pass:");
    lcd.setCursor(0,1);
    while(j<7)
    {
      char key=customKeypad.getKey();
      if(key)
      {
        pass[j]=key;
        lcd.print(key);
        Serial.print(key);
        EEPROM.write(j,key);
        j++;
        beep();
      }
    }
    lcd.print(" Done......");
    delay(1000);
  }
  lcd.clear();
  lcd.print("Enter Password:");
  lcd.setCursor(0,1);
  customKey=0;
}

void beep()
{
  digitalWrite(buzzer, HIGH);
  delay(20);
  digitalWrite(buzzer, LOW);
}