The money grabber

Do you want to save money for your personal dream project?
Let the digital coin safe keep account of your coins!

Introduction to the project

Short description of the concept

Our plan is to manufacture a coin safe that measures the amount of money put in the safe. To achieve this, we use an accurate digital scale that measures the weight of the coins and distinguishes their value according to it. The safe will also have an LCD screen that outputs the current balance of safe in euros and tells the time. The top side will have a door that is opened by a servo motor and the coin box can be removed after opening the top door. Both the LCD and the door will be operated by a pressable button. Material for the safe will most probably be acrylic.

Description of how you arrived at your design

One suggestion was to make a responsive toy that transforms voice to higher pitch, but most of us decided that it would be too annoying. Eventually we decided that the coin safe would be a suitable project.

Other options you considered while deciding on your design

So far, the design has of course been transforming throughout the first weeks. One of the ideas for safe functions were for example make the coin box inside be rolled out by a motor, but that was changed so that only the top will be opened by the motor. Another idea was to make the safe lever function as a real lever in a safe does: by turning the lever the locks and the door open.

Design sketches

LCD screen

LCD screen
HighFi Sketch

Contact Us

Giuseppe Superbo

Juho Holmi

Nelson Lemercier

Clément Charton

Bill of materials

arduino uno board

1 x Arduino uno rev3

Single-board microcontroller to manage the sensors and the actuators of our digital coin safe

micro servo 9g

1 x Micro Servo tower pro SG90 9g

The servomotor is used to open the safe door.

LCD screen

1 x 162B-CC-BC-3LP Alphanumeric LCD Display

Screen used to display the time and the amount of money in the safe

Load cell

1 x Load cell TAL220

Load cell used to deduce the amount of money in the same from the weight

Load cell amplifier

1 x Load cell amplifier HX711

Amplify and convert the signal from the load cell for the arduino


4 x Pushbutton Switch - 12mm Square

Used to open the safe, set time and set an amount of money

Battery cable

1 x battery cable

Cable for the external power supply

Battery holder

1 x battery holder

External power supply for the LCD screen and the servo motor


4 x 100 ohm resistance

Used for the wiring of the buttons

red led

1 x red led WP7113ID

Indicate if the door can be opened or not

green led

1 x green led WP7113LGD

Indicate if the door can be opened or not


3 x 499 ohm resistance

Used for the wiring of the LEDs and the LCD screen