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BAKUDAN Mk.1 (Airsoft Prop Bomb)

Updated: Sep 21, 2023

So, I began a little project of building prop bombs that are fully functional for our October charter game. These will be used in various game modes like Bomb Disposal, Domination and Sabotage.

I got the idea from military training regimes and decided to do some research to make them into a functional game where the purpose is to defuse them.


Decided to go for a simple and accessible route for the wires to allow for later modifications
Stage 1 - decide on the wiring route

I looked around online and found that you can buy a premade timer like the Nootropic Design Game Timer Pro. However, this item is essentially a barebones clock with timer function and has wires you can cut or remove or a keypad to stop the timer. While it seemed like a good product, it does not allow any flexibility for programming and upgrading it beyond a 4 digit password or wire sequence. It is also notorious for shorting out and getting hot. For me, this makes the application of the device somewhat limited and impossible to repair.

That is where I decided to make something more unique with more functions and practical use that people can enjoy more and also I can gain a sense of achievement for creating something myself.

Enter the AOJ Bakudan Mk.I (BD1 for short).


  • 4 - 12 digit password

  • Various sound effects

  • Various light sequences

  • Fully customised programming

  • 3 game modes installed

  • Customisable timers for game length, arm time, disarm time & detonation time

  • Winning team announcements

  • Domination counters

  • Hand made design

  • Sturdy waterproof case with wood subframe and aluminium faceplate

  • Completely modular and customisable

  • MP3 Audio capable.


The Interior

First I ordered an Arduino UNO Rev 3 board from Amazon as a set with various parts I could use as well as a breadboard and other parts to build the basics.

Now, it is worth mentioning that a lot of the parts were bought using donations from AOJ leaders and members. Their donations, made this possible and without them, we would not have such an amazing item to use.

Part List

(Remembering they will be 5V to work well with the board)

Required Tools

Most of these I got from home centres and hardware stores after research.

  • Voltmeter

  • Wire strippers

  • Wire cutters

  • Flux

  • Soldering Iron

  • Screwdrivers

  • Assortment of nuts, bots, washers, spacers and screws

  • Hard case

  • Acrylic sheet (3mm)

  • Aluminium sheet (2mm)

  • Epoxy Resin

There are some other items for design purposes and you do not necessarily need aluminium sheet, I chose it more for strength and design purposes. If you do not use aluminium, then you need something stronger than 3mm acrylic and it will cost a lot more than aluminium. But, these extras and what types you go for are your choice. Just made sure the interior is at least 20cm x 10cm x 10cm (W/D/H) to fit it inside without being too tight.

Once I had all my items, I was ready to begin. The first stage was decided what will be plugged in and to where.

Since the keypad uses 8 pins and the LCD uses 6 pins (excluding the power, ground and potentiometer cables), I grouped them as best I could allowing for the breadboard to handle the multiple inputs and extensions.

Programming Code

Once I had everything plugged in I needed to refresh my C++ knowledge and began programming the input and output pins. An easy program for me to test this is a simple calculator with an addition and subtraction ability only.

This enabled me to test the input and make sure the LCD was producing the desired results. After this I had Ben had to move on to the functions in more detail and add a main menu, game modes, variables and the splash for when the games are won or lost. THIS was the time consuming part, as I only learned basic C++ before and partly relied on forums to gather information on functions I had never used before.

Thanks to a man (or woman) called XFPD, I was able to learn the basic functions I needed and modify the code to my liking.

As my mentor, XFPD assisted in correcting my mistakes and educating me to make the first game "Search & Destroy". After this was complete and simulated on Wokwi to test it works.

After two days of trial and error it worked with zero problems and compiled perfectly. now, the challenge was to add a Sabotage and Domination game mode.

With the device made, the program installed, I felt that I wanted to modify it further.

I added a key switch to act as a power switch and to prevent anyone turning it off by accident (or cheating to reset it). Two coloured buttons for red team and yellow team for the domination game and a single channel relay, which I then modified the code to add more options for the "BOOM". In this case I want a red strobe light, louder speaker and perhaps MP3 output to play sound files.

The software is also branded with the creator name and AOJ's name on the LCD on startup as well as a battery check to give current battery voltage.


The case

Stage 2 - the case and layout design

One of the other leaders bought this case. It is thick hard polypropylene case designed for carrying a firearm, drone, camera or other sensitive equipment and come in a range of sizes. It can withstand heavy weights and is waterproof.

This one cost about ¥5,000 and came with various foam inserts, but I took them out as having electronic components on foam is a bad idea, not matter the voltage. We all saw what happened to Samsung batteries a few years ago and a circuit with a processor will draw a fair amount of voltage and will get warm depending on the processes you create. In this case, I am using 56% of the processing power, so nothing that can burn or melt should touch the circuit and air-flow is essential.

That is where the designing phase came in. I wanted the ensure that the entire contents can come out in one piece and allow easy access and modification. I began designing it to have am acrylic base with wood subframe (wood has been treated to be fire-retardant), acrylic top with aluminium sheet for the face. I also added handles to make lifting out the unit easier and it fits snugly inside without any rattling, and lets me lift it out quickly and easily to change batteries. I also added a small compartment inside with spare resistors, cables, power cord, USB cable and such for repairs on the go.

Bomb design stage 1
Stage 3 - Basic layout is complete

With the basic wooden frame in to support it all and keep it sturdy, just in case that one guy presses buttons too hard... I just need to attach the base acrylic sheet and all the components, then cut the top sheet, which will also double as a template for grinding the aluminium sheet. The best and most simple part is the handles on top. They will be the method to lift it out of the case as well as pushing it down when the case is closed to prevent any movement.

As you can see the base layout is done and the next stage is cutting the aluminium sheet to attach to the top, put some protective glass over the screen and then fix down the components inside and it is done. However, I am liking the black, sheek look of the face place, so the final design is somewhat undecided.

The final stage is to finish the design. I wanted to use rough aluminium sheet, so purchased a 3mm thick sheet, cut it by hand and finished it with a dremel. I have also fixed all the cables in place and just need to make a battery holder as well as install some more speakers.

Hand made, programmed and original design by Ben Merritt.

Stay tuned for more updates soon.

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Sep 05, 2023
Rated 5 out of 5 stars.

Looks great! I look forward to seeing this thing in-game!

Bravo Nineteen
Bravo Nineteen
Sep 05, 2023
Replying to

Thanks. It’s getting there. But waiting for two imported parts to finish things off.

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