Introduction: CUBEX - an Arduino Sensor Safe

About: We are two young inventors, Kousheek Chakraborty and Satya Schiavina. We like using digital fabrication, electronics and various other fields of knowledge to create projects that focus on simplicity, efficienc…

Ever wondered if you could control things with the power of your gestures? Ever wondered if with the help of sensors you could make things look as though it works by magic?

Well meet CUBEX, an Arduino sensor safe that permits you to do what you always wanted to do! To magically open up your very own safe! This safe will open up without even you ever touching it!

At home I wanted a space where i could keep my secret ''treasures'' well away from the reach of my siblings, parents or even friends. This got me thinking to a rather different design of a safe! With the invention of CUBEX, you don't need keys neither do you need a number lock, you will unlock it only with the power of your gestures. To play on with the magical idea we added in motors so that the box actually opens up completely by itself, somewhat like a scene from a Sci-fi movie!

Watch the video on top, to have an understanding on how we made it and how it will look once its done.

To see how it works, and to make the new generation of the SENSOR SAFE theme follow on!

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Step 1: Overview of CUBEX

The uniqueness of CUBEX is that instead of using a number lock or a key it permits us to unlock the safe with the power of our gestures. This design wipes out the never ending problem of loosing one's keys and makes it impossible for an intruder to even guess how it works!

To make this possible we used various sensors positioned around the box at specific areas. As we weren't ever physically touching the box we set parameters to each sensor, that when performed in the right sequence would unlock itself, in a rather mysterious way. To play on with this magical idea the parameter that we set made our gestures one of a magician's. Then as though magically CUBEX opens up automatically, opening the safe and permitting you to access your treasures.

Step 2: Materials Needed


  • Plexiglass ( Lasercut 4mm thickness, colour of your choice)
  • Cardboard ( for prototyping)


  • Servo motor( used in opening the box, 13 kg / cm (4.8V), 15 kg / cm (6.0 V) 40mm x 19mm x 43mm
  • arduino uno(you could use any that you have)

  • Ultrasonic Sensor (2 of these, one for left and another for right, you'll see why, in a late step)

  • 1 photoresitor

  • 1 10k ohm resitor

  • jumper wires (lots of them)

Step 3: PROTOTYPING : Making a Cardboard Model

To be able to visualize and have a better understanding of our safe, we decided to make a cardboard model. We then positioned the sensors and motors to make the whole concept work. We transferred this model into a ready for laser cutting, easily printable for you.

Step 4: Designing and Modelling

Using a graphic design software (inkscape, link to this free software below) we designed the parts we would need to make CUBEX .

Then we took the design to a nearby workshop to get the parts laser cut. Attachment below for the designs. After laser cutting be sure to have 18 individual pieces.

Link to download :Inkscape.

Step 5: Parts Lasercut

Once you have the parts laser cut you can move on in a rather time consuming job so get some help! Make sure to peal each and every piece from the cover, when you're done, verify that you've got 18 pieces on the whole.

Step 6: Assembling the Big Box ( DRY FIT )

Start by assembling the big box (outer one) to just get familiar where all the pieces go, this will make a flawless work in the sticking process and also will make it go faster. The finger joints hold well but later on dabs of superglue will give it more rigidity.

Step 7: Assembling the Inner Box ( DRY FIT )

Do another ''dry fit'' for the smaller box (inner compartment). The pictures will help if any doubts, so make sure to follow them...

Step 8: Adding the Servo's & Inner Box's Supports

The design of the inner box, is one that can be removal if by chance the user needs to access the electronics. Glue in the flaps with superglue on the outer and inner box. The outer ones act like a ledge for the inner one.

Two small supports for the servo motor also will be glued in, you will notice two holes to mount the servo this will be done in a later step. Once done let the glue dry.

Step 9: Circuits and Electronics

Simply follow the first picture, make sure to tin the wires well before soldering to ensure good connections. We used a small breadboard and lots of jumper wires, if you like you could try making a custom PCB for this project ( it will neaten things up). We used dabs of hot glue to stick the wires to make it less messy.

Step 10: Fitting in the MOTORS, SENSORS and ELECTRONICS

You will notice that the slots and holes for the motors, sensors and switches are around 1 mm smaller. We wanted the pieces to fit in snugly, with a light sanding you can press in the components making sure they are flush with the outside, to make CUBEX look sleek.

Step 11: Assembling CUBEX!

You need to assemble the box exactly how it was done for the ''dry fit''. Although this time apply dabs of superglue on the edges and joints of both the interior and outer box.

Then simply slid in the inner box, making it sit on the ledge. Set the servo at its zero point and attach the lid by fitting in the servo horn. Finally put in the screw and you're done!

CUBEX is completed, let's move on to the code!

Step 12: Testing the Code

Now that you've built CUBEX, upload the code that is attached below onto your arduino. You'll have to download arduino's IDE, to upload the code. The code has a certain number of parameters, that once executed correctly allows you to open the box. The moves, according to what we've programmed go like this (you can always edit them to your liking by modifying the code)

  1. your left hand should be about 2 to 10 centimeters away from the left ultrasound sensor, and for your right hand 8 to 16 centimeters away from the right sensor
  2. next, your left hand should be 8 to 16 cms away from the left sensor, and your right hand should cover the photoresistor so that the light drops below the threshold
  3. then, your right should be 2 to 10 cms away from the right sensor, and your left hand needs to cover the photoresitsor, again till the light drops below the threshold
  4. finally both of your hands need to be 5 to 13 cms away from each sensor respectively

Now step back and watch CUBEX magically unlock itself.


The moment of truth! It's time to test your creation, its time to test CUBEX. Let's find out the power of your gestures.

Start by plugging in your Arduino to the computer.

Next perform the moves, mentioned in the previous step,

And presto! The green light will turn on, the motor will swing the lid open and there you have it, you, have successfully unlocked the safe in a magical manner.


Step 14: DONE!

There you have it! Now go impress and amaze your friends with your very own CUBEX. I got amazing reactions, the reactions which makes you wonder how on earth did that happen. CUBEX was a really fun project to make and we are really happy with the outcome. Other than the cool features, CUBEX is also very useful, this could be a simple safe for you to build and to keep your personal stuff in it.

What stands out I feel is the originality of this project, I THINKl future safes should look something like this and trust me if someone doesn't know the sequence it's nearly impossible to break in.

We already have ideas for version 2.0 and we will be soon publishing it here so stay tuned!

Hope you enjoyed the instructables, feel free to drop a question or some feedback in the comment section and don't forget to VOTE for us in ALL the contests!


Cardboard Contest 2017

Participated in the
Cardboard Contest 2017

Microcontroller Contest 2017

Participated in the
Microcontroller Contest 2017

Sensors Contest 2017

Participated in the
Sensors Contest 2017