Table of Contents

DIY Mini Safe Locker: Locking Mechanism Using Corrugated Sheets and a Servo Motor

DIY Mini Safe Locker Using Servo
Project Description


A mini safe locker comes in handy when you want to keep your precious little belongings safe but also close to you(r heart). Though the ones used at homes require a) a LOT of metal b) next-level tech, what we’re making is our own version of the DIY mini safe locker that kids can use to keep their cookies safe from their siblings

Components for making this safe locker are available in the evive Starter kit and it can easily be programmed in PictoBlox – our graphical programming software based on Scratch blocks. You can download it from HERE.

Ready for making your own safe locker? Let’s begin!

Preparing the Box for the Safe Locker

For making the box for the safe locker, we first need to make a functional safe box that would help us store valuables in it. The box then needs a door, doorknob, and a locking mechanism.

We will start with how to make a safe locker with cardboard, but for now, we are going to make the safe box using the corrugated sheets. 

Making the Top and Bottom of the Safe Box:

First, let’s make the top and bottom of the box.

  1. Take a yellow corrugated sheet of 30 cm * 15 cm and make a line at the center of the sheet and 
  2. Now cut along the markings we would get two sheets of 15 cm * 15 cm each of which would act as the bottom and top of our safe box.Mini Safe Box making (2)

Making the Sides of the Safe Box:

The next step would be making walls for making the safe locker.

  1. For making the four walls, take a red corrugated sheet of 60 cm * 15 cm.
  2. Mark three lines on a red corrugated sheet at every 15 cm we would now get four equal squares each of these squares of dimension 15 cm*15 cm.Mini Safe Box making (3)
  3. Next, cut through the first layer along all the three lines designed, which makes the sheet easily foldable, thus removing the mess of gluing the walls together to make the wall of the safe box.Mini Safe Box making (4)

Making the Door of the Safe Box: 

We would need a door to access the valuables inside of the safe box.

  1. Thus, mark a square of 10 cm *10 cm inside the last square on the red corrugated sheet on which we have marked the walls.Mini Safe Box making (5)
  2. Cut along the three sides of this 10 cm * 10 cm square, but make sure not to completely cut through the fourth side.
  3. Create a slit on the fourth side through the first layer, this will give the door, a hinge structure to make the opening and closing of the door smooth.Mini Safe Box making (1)

The door is done!

Making the Door Handle

To open and close the door easily we would make a small doorknob or the door handle.

  1. Take a circle master and mark a small circle on a piece of corrugated sheet of approximately 5 cm diameter.Mini Safe Locker Making (2)
  2. Cut out the circular disk for a knob.
  3. Take a straw and cut a 1 cm tube from it for making the shaft of the doorknob.
  4. Take this straw piece and attach it to the doorknob, with this our door handle is ready.Mini Safe Locker Making (3)

Thus, the different components of the Safe box are ready!

Designing the Interlocking Mechanism

We are going to use the servo as the main element of our Interlocking mechanism. Where a part of the door gets hooked to the servo horn thus keeping the door of the safe locker closed. Thus, let’s make the structure that will interlock with a servo motor.

  1. Take another small strip of a corrugated sheet of about 10cm * 4cm size and mark the two lines at an equal distance from one another.
  2. Now fold along the markings and by using some hot glue make sure the bends hold its shapes and all the bends are perfectly perpendicular.Mini Safe Locker Making (4)

Once done, keep it aside.

Assembling the Mini Safe Locker

We will start assembling the components of the safe box that we have prepared.

  1. Take one of the two yellow 15cm * 15cm sheets which would act as the bottom and now attach the 3 walls of the safe perpendicular to it. Make sure to keep the fourth side open.Mini Safe Locker Making (1)
  2. Also, attach the door handle assembly we have prepared above near the opening edge on the fourth side using the hot glue.Locker Interlocking Mechanism (2)

Completing the Interlocking Mechanism

This interlocking mechanism will provide security to our safe locker.

  1. Thus, take the U-shaped piece of corrugated sheet and attach it at the back of the door exactly behind the door handle using hot glue.Locker Interlocking Mechanism (3)
  2. The servo motor acts as the actuator which controls the locking mechanism.

But before attaching servo, we would set the angle to 90 degrees by using the evive firmware menu.

Setting the servo angle

Setting the servo angle has never been this easy, the plug and play feature of evive. Just follow the steps:

  1.  Attach the servo to evive’s servo channel 2Conenction Servo for Mini Safe Locker
  2. Switch ON evive.
  3. From the menu, select Controls
  4. Navigate to Servo
  5. Than select Servo 2
  6. Use potentiometer 2 to set the servo angle to 90°

Disconnect the servo.

Attaching the Servo Motor

Before we attach the servo motor, let’s first attach servo horns to it which will hook the U-shaped structure in it.

  1. Take one single-sided and one double-sided servo horn and fix them both to servo motor using a 20mm servo screw.Locker Interlocking Mechanism (5)
    evive Notes Icon
    Make sure not to disturb the servo angle while attaching the horn.
  2. Attach the servo motor to the door frame using some hot glue such that it interlocks with U- shaped corrugated sheet that we attached on the inside of the door.Locker Interlocking Mechanism (1)
  3. Once done, close the fourth side by applying some hot glue to the edges of the fourth side.Mini Safe Locker Using Servo (2)

With this most of the assembly is done but we need to make sure if our locking mechanism works properly or not before sealing off the top.

Checking Whether our Locker Works Perfectly?

Once again, connect the servo motor to the servo channel 2 or s2 channel on the evive.Conenction Servo for Mini Safe Locker

Upload basic PictoBlox code by using the PictoBlox to the evive.

Use the slide switch 1 on the evive to lock and unlock the door of the safebox.

Completing the Assembly of the Safe Locker

Now when we are sure that mechanism in our safebox works perfectly as we tried locking and unlocking the safe box. We will close the safebox by attaching the top.

Take the other yellow corrugated sheet of 15cm*15cm and close of the top of the safe locker using some hot glue.Mini Safe Locker Using Servo (1)

With this, the assembly and the connection of the safe box are ready!

Writing the PictoBlox’s Code

Our safe locker will be operated with the help of a slide-switch of evive. Let’s write the code in PictoBlox.

  1. The program starts executing forever when evive starts up.
  2. When the slide-switch is pushed up, the servo angle changes to 100° which results in freeing the U-shaped structure which in turn opens the door.
  3. When the switch is at the center position or down position, the servo angle changes to or remains at 0° and the U-shaped structure gets hooked up to the servo horns thus the door remains locked.Safe Locker Code

Making the Safe Locker Password Protected

For the advanced version, we will create a code using pictoblox which will help us open and close the locker only after entering a two-digit password for the safebox. 

  1. The code, as usual, begins when evive starts up. We will set the password in the code itself. 
  2. When slide switch is in the down position we would be allowed to enter the password by using the potentiometer 1 the display would show the entered password in real-time and access status of the door. 
  3. As we are going to enter the password using the potentiometer, which gives a value between 0 to 1023 and we need our password to be any number between 0 to 100.
  4. Thus, we are going to use the map function for the same. Once the values are mapped, we need to check whether the slide-switch is up or not and if the value entered by us is similar to the password. map function block
  5. If yes, then the servo angle changes to 100 degrees thus unlocking the door. And “Access Granted” is displayed on evive’s screen.
  6. If no, the servo angle is set to 0 degrees and the door is locked and TFT displays “Access Denied”.Safe Locker Code 2


With this, your DIY mini-safe locker is ready!

Project Downloads - Code and Files

Circuit Diagram

Circuit Diagram DescriptionCircuit Diagram Fritzing Diagram

Attach the servo to evive’s servo channel 2

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