Arduino Defuseable Bomb, Perfect for Airsoft Games! (with Timer, LCD, Keypad, Sound and More!)





Introduction: Arduino Defuseable Bomb, Perfect for Airsoft Games! (with Timer, LCD, Keypad, Sound and More!)

This is a project I made a long time ago, but decided to upload anyways, feel free to ask me about it!
The bomb has several features:
- Password input by keypad to arm the bomb
- Timer/count down
- Sound
- Flashy LEDs
- Defusing via the password
- LCD display
- Keypad
- Simple to edit and change

So to get started you would need:
- Arduino
- LCD (I used a 16x2 from sparkfun)
- Potentiometer for the contrast on the LCD 
- Keypad (again from sparkfun)
- Jumperwires
- Resistors for the LEDs (I used 330 Ohm)
- Piezo/buzzer
- LEDs

Step 1: Assembly

Connect the components as according to the circuit schematic

Step 2: Upload the Code

Upload the bomb project4 code to your arduino, and add the following libraries: Keypad, Tone, and liquid crystal to your libraries folder in the arduino folder

and now you're ready to use the bomb!

First edit the time in the code, to match your needs, then start the arduino and enter your desired password, then the bomb timer will start, and you can press the * to begin defusing the bomb, if you press a wrong key, pressing # will delete what you've written. If you write a wrong password, or the timer reaches 0, the bomb will "explode"!

Feel free to ask :)

10 People Made This Project!


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4 Questions

Hi. How do i wire the LCD if i have only 4 pins(gnd,vcc,sda,scl)? I have a small board on the 16p. Do i need a different cod? Pls help me.



Replace your LiquidCrystal.h library with LiquidCrystal_I2C.h that you can find anywhere on the net. Wire the SDA to terminal A4 on your Arduino and SCL to terminal A5.

Then add this to your code:

LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

//LiquidCrystal lcd(7,8,10,11,12,13); // the pins we use on the LCD

You may need to alter the LCD commands to something like:



lcd.print("Code: ");

A bit of reading on the net will also help out, but that should get you going for now :-)

"menu principal was not decleared in this scope"- how to fix it?


"menu principal was not decleared in this scope" ----------how to fix it?

I keep getting a exit status 1 message when I upload. Do you know how to fix this?


thank you :D it worked like a charm:

8 replies

Glad you found it useful! Your prop looks great!

Hey, I am having a issue with the LCD screen. When I turn it on nothing is being displayed on the screen, the keypad, LED's and buzzer work fine, when I enter the code and it start counting I am able to enter password again after the * and it is being defused or explode but the LCD screen itself does not display anything. I am including the picture of how the LCD is displayed


I'm having the same issue

hi, have you found a solution i have your same problem.....the lcd makes only a long line like in your photos...

did you find a solution?

do you have Potentiometer for the contrast on the LCD ?

I may found the reason for the LCD to not work correctly.....

The schematics of the LCD does not show which order are the pins, if they are VSS, VDD, VO, RS, RW, E, D0, D1, D2, D3, D4, D5, D6 ,D7, A, K, or other way round... I will Re-solder them and we will see if it helps.

Do you have any detailed photos of your wiring ? I'm having some trouble getting this to work

hi, how to Connect This type oferta display? it Has some addons: potentiometr, gnd (-?), vcc (+?) , sda, scl. Also led and power with jumper on it. how can i adjust it to the shame.

1 reply

Hi. i'm having the same LCD. Did u have any luck?


Cool i fixed it with a 4x4 Keypad. I needed to change the code. Below is the code:

Also i added a image of the pin on the keypad.

//replace these lines in the code when u have a 4x4 instead of 3x4 keypad.

//and add a cable to pin 6 which is pin 1 on the keypad.

const byte ROWS = 4; //four rows

const byte COLS = 4; //four columns

char keys[ROWS][COLS] = {






byte rowPins[ROWS] = {A0, 5, A1, A2}; //connect to the row pinouts of the keypad

byte colPins[COLS] = {A3, A4, A5, 6}; //connect to the column pinouts of the keypad

//Pins 8, 7, 6, 5 on the keypad should be connected to digital pins A0, 5, A1, A2 on //the Arduino.

//Pins 4, 3, 2, 1 on the keypad should be connected to digital pins A3, A4, A5, 6 on //the Arduino.

2 replies

can you please upload the full code you use, i also have a 4x4 keypad and im having issues to verify the code, you realy help me

In the code I found its only about 6 lines. I also only use 1 analog pin freeing up all the analog pubs.

Hey!, is there anyway to amplify the sound in an easy way?


I have a problem. Everytime i klick on the upload button, i get this Error:

C:\Users\Fabian Scheuermeier\Desktop\bomb_project4\bomb_project4.ino:6:20: fatal error: Keypad.h: No such file or directory

#include <Keypad.h>


compilation terminated.

exit status 1

Error compiling for board Arduino/Genuino Uno.

Can someone help me? I dont know what to do.

1 reply

In documents you have the directory "Arduino"
Copy the "PROJECT" (in a folder)
And in the folders "KEYPAD", "CRYSTAL LIQUID", "TONE"

Then the upload will come

hi dear MaltheF

I've loaded the circuit according to your instructions, uploaded a program.
But I do not work LCD (I used a 550 ohm potentiometer)
I do not even use Leds (330 ohm resistors)
Buzzer works

LCD does not work or when I do not connect anything else

Please help me
well thank you

sorry for englis

please can someone send me the code to

So, over the past year I have this down now. I have the complete code to bring the keypad down to one pin, Program the time in steps from the keypad instead of having to code it all the time. I'm still working on the Serial LCD Screen to get it down to four pins instead of all the pins being used. I'll get it all together in the next few days and post it. I'll look for the schematic for the keypad so that nobody has any questions on how it works. I'm still looking for the right container for it to make it look realistic.