Mil-sim Airsoft Bomb Prop

First of all, thanks to all the great people here that helped me through my first project!

This is a project I have been working on for a while. We usually just use egg timers to simulate explosives in these games, but I figured it was time for something a little more realistic looking.


How it Works: The bomb must be attached to the tether (which is locked to a tree or other immobile object) before it can be armed, this ensures that the bomb can only be armed in the designated area. If the tether is removed at any time while the bomb is on, it will detonate. It can only be turned on and off with an electronic key switch, I have 2 keys, one for each team leader/ref. To arm the bomb a 7 digit code must be entered. This starts a countdown. The countdown can be interrupted at any point by pressing the disarm button, when the button is pressed the user is asked for the disarm code, this is a separate 7 digit code from the arm code. After the disarm button is pressed, the bomb will wait 15 seconds for a code to be entered, if the code is correct, the countdown will end and the LCD will display "Bomb Disarmed". If the code is incorrect no message will be displayed, press the reset key ( the "*" key) and try again. If no code is entered after 15 seconds, the counter will restart and 15 seconds will be subtracted from the time left. When the countdown reaches 0, a buzzer is sounded and the LCD will display "Have A Nice Day". It sounds more complicated than it is, just watch the video.

Variables: - can be changed at any time. Countdown time 0hr:2min:30sec Arm code: 7355608 Disarm code: 1234567

The Bomb can be powered by a normal 9v battery, or a 12v 1.6A/hr battery. Right now I have it attached to a small buzzer, but it has more than enough battery capacity to run a siren, strobe, radio, electric detonator, servo, or just about anything that would be useful to alert people when the bomb is detonated.


This is my first project, so i'm assuming that there are quite a few errors and places where I made an error, then reversed to to make the code work. Feel free to suggest any alternate ways to achieve this (if the code is clean enough to even be readable by other people, that is).

Wery cool!

Love the idea, and the implementation.

Made me want to switch back to airsoft, from paintball… :smiley:

a a co2 canister in line with a paint canister with a spray nozzle with a solenoid in between.

(C02)----(PAINT)-> NOZZLE ~~ ||~~ ~~ Arduino~~

small detonator unter a plastic bag of paint.

somewhat funny that thing :0) Good Job

just googled a bit. really wonder how companies like this ship their products :)

Would be funny to have a couple of colored wired that you had to cut in the right order.

how did you layout the pinout??? so far i was able to plan out:


keyswitch wired between battery and arduino to set ready mode

enter code followed by pound to arm
enter seperate code followed by pound to disarm
any other presses decrease time by ten sec.

this is my first project as well. i have the code portion covered
but im lacking in the knowledge of what pin can do what.
is it possible to wire the keypad to the analog pins to free up some of the digitals??? id like to add a flashing rgb led so thats another pin there…

That would take some explaining if you got stopped by the rozzers with it in your boot.

(I hope the yanks can understand that ;) )

forgotten, if you use a serial LCD like I did, then you only need to use 1 digital pin for it, that frees up some digital pins. If you already have an LCD, sparkfun sells a serial backpack for LCDs, i’m not sure which ones it will fit though. You can probably put the buzzer on an analog pin, I set mine to trip a relay, then connected the buzzer directly to my 12v power supply.

lol, yeah i didnt get a serial.. ill have to toy with it and see what i can do. thanks for the reply..


I'm actually working on this exact same project.

I came via a different route, I wanted to put mercury switches in the device but needed some form of latching relay to do it and it took off from there.

I would love to get some shots of the inside of your device if possible (I'm heading towards a lexan box myself with all the guts inside except the keypad since i'm in Seattle)


Sure, I can get some pictures up tomorrow. I’m still in the process of redesigning this so I can sell them, but I have a working design right now. To cut costs, I followed the tutorial to make a bare-bones arduino, and am now using that instead of the pre-built unit I started with. I’m trying to keep the project updated with pictures and video at I have a really crude wiring diagram here:

Heres a picture of the inside, i'll get better ones when the college work lets up.

The 8 pin connector is for the keypad (only 7 pins are used), the three pin one is for the LCD, and the various 2pin ones are for the 9v -12v power in, power switch, buzzer, and tether. I used a weather proof project box from NTE.

Wisdum- I am currently building a project extremely similar to this, except in my version the 'bomb' is buried underground, IED style. I have rigged a solenoid valve to a compressed air tank, and when activated it sprays washable paint upwards out of a shower head, marking anyone who would have been killed by a real bomb. It would be a great help if I could get a schematic and parts list (preferably with a website or store name where the parts came from)

Thanks /me

I'm currently working on my website, but you can find a basic schematic and description at . I'll try to add a parts list later today. I got everything from sparkfun and digikey.

To translate Mike Mc.

rozzers = police boot = trunk

All good fun, but definitely some scope for serious misunderstanding with the authorities.

Your police all carry guns for heavens sake! Over here we have only just let them have cars and they do enough damage with them!

I looked over the schematic and it looks very nice and clean. Realizing that I have most of the parts needed as spares and stuff from previous projects, all that I really need in the way of a parts list is just the website for the keypad, and the sparkfun model number for the display.

Thanks again, /me

Thats is freaking awesome.

SI, it hasn't really been a problem for us. Most of the time the police are more interested in what airsoft is, and want to try out some of our gear, and I drive around with some pretty serious hardware. For most games I have nothing less than 2 M4A1s, 1 G36c, 1 sig552, 2 ak-74s, 1 M249 SAW, 2 mp5ks, 2 Beretta M9s, 1 M1911, 6 M67 Frag grenades, 6 flash bang grenades, 2 claymores, 40 or so magazines, 3 tac-vests, and of course, the bomb prop. For games we always notify state and local police (and campus police when using our University field), and we often have members of law enforcement playing in the games with us.

Electrical Juggernaut, this is the keypad I used for the first design:

I used a 4x4 keypad in later designs that I got at a local shop, it's the same setup, just 1 extra pin.

And this is the serial LCD that I used: