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

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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 :)

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    Made with Math Contest
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186 Discussions


Reply 4 years ago on Introduction

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


Reply 3 years ago

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

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.


Question 5 weeks ago

Hello! I wanted to ask if i can use any other LCD or does it have to be from sparkfun? Thank you!


3 years ago

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.

3 replies

Reply 3 months ago

You, sir, are a life saver. Thank you very much!


Reply 1 year ago

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


Reply 3 years ago

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


2 years ago

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.

1 reply

Reply 4 months ago

Did you ever figure out how to change the LCD Screen to four pins?


Question 5 months ago

Has anybody fixed the bug with the ##:00 minutes?


Tip 5 months ago

For those with I2C (IIC) LCD, you can transfer the keypad to the digital side, then move the LED's and the buzzer to free up the analog. It will require minor code changes tho, but most of what I used was based on this instructable.


Question 5 months ago on Step 1

Hi! Is there a version of this where an IIC (I2C) LCD is used? or is it just a simple conversion? My only working LCD is a 16x2 IIC LCD. Can you help me?