Digital Scale Using Ultrasonic Sensor ( in Freeform )




Introduction: Digital Scale Using Ultrasonic Sensor ( in Freeform )

Today we are going to make a simple portable Ultrasonic based Digital Scale, but there is a small twist in it, we are going to make this project in Free-Form, without using jumpers or pcb, instead we will use thick copper rods, so let’s get started!



1. Arduino Nano

2. Ultrasonic Sensor (HC-SR04)

3. 0.96" OLED

4. 0.8mm Copper Wire

5. 0.6mm Copper Wire


1. Soldering Iron

2. Soldering Wire

3. Helping Hands

4. Solder Fume Extractor

5. Plier

6. Drill Machine

Step 1: Watch the Video!

Step 2: How It Works??

Let’s understand how this project works, first of all we will measure the distance using Ultrasonic sensor, which acts as an input, next Arduino will do the computation and display the results on an I2C OLED display.

also, for Ultrasonic Tutorial, refer this post which explains all the basics of Ultrasonic, like "how to set up", "how to calculate distance", etc

similarly, we have a tutorial on OLED display, which would be very helpful for begineers, so click here !

Step 3: Let's Connect It!

Since this project and entire process of free-form electronics is complicated, let’s write the code and test everything on jumper wires before we start soldering. for which, we will follow these connections:


GND - D2



VCC - D5


Vcc - 5v

Gnd - Gnd

SDA - A4

SCL - A5

you can refer to the circuit diagram and Fritizing file attached in this step for better understanding.

Step 4: Press the Upload Button.

First we include the libraries of SPI, Adafruit GFX,Adafruit ssd1306,Then, initialize the OLED, define the Trigger and Echo pins, define variables,Then in pin mode, necessary definitions were added, along with a sweet start-up animation message saying “Electronic scale by Mission Critical” Next in loop section, we did the calculations of Distance in centimeter, which we discussed in Ultrasonic sensor tutorial ( link attached in previous step), next we saved the distance data in “distance” variable and extended it to appropriate cursor locations, and then we are done! Simply upload this code to Arduino nano.

( if you don't understand code, its alright, simply download the code attached here and upload it on your board, and wire everything as shown in previous diagram and we should be good to go! )

Step 5: Prepare the Plans of Design

honestly, this is my first free-form electronics project, so i tried to make a rough sketch of the design idea on a notebook ( my notebook has grid lines thanks to instructables :P), later i used ruler scale to measure the dimensions of the modules and later i used Fusion 360 from autodesk to make a CAD diagram and rendered out how my project should look!

Step 6: Straighten the Wire

since the wires come in a roll or you might tangle it while handling, it won't look good for free-form, neither it looks professional, so we nee to straighten up these wire before proceeding further, so follow the steps below:

  1. cut the wire to approx 10 cm length ( to avoid slipping of wire from chuck use longer lengths ).
  2. open the drill chuck.
  3. make a small bend at the first end of wire ( which goes to drill chuck).
  4. tighten the drill chuck.
  5. hold the opposite end with pliers at slightly angled manner ( create tension).
  6. trigger the drill at slow rpm.

PLEASE BE CAREFUL WHILE DRILLING ( if you are not comfortable handling drill don't hesitate to ask for parents help)

Step 7: Solder the Base

first we decided the footprint of our project by measuring components and referring to CAD diagram, to start we need a solid base, we will use 18 gauge wire to do this structural step.

our Base is a Rectangle of 52mm X 34mm, so we will cut 2 pieces of each 52mm and 34mm of straight copper wire using Pliers ( BE CAREFUL WHILE CUTTING ). once done, we will use Solder iron to solder these joints with visually perpendicular (90°).

Step 8: Solder the Ultrasonic Sensor

once the base was ready, we will next solder the Ultrasonic Sensor to Arduino since that will determine our vertical height of, so we will simply push the Ultrasonic into Arduino Board, such that " GND - D2 : ECHO - D3 : TRIG - D4 : VCC - D5 " these connections are made and simply solder it with arduino ( make sure it too make a 90° angle).

Step 9: Prison the Arduino Nano

once the ultrasonic sensor is packed, we get our height room, which comes to around 24mm. so let's cut 4 pieces of 24mm for height, and solder it at 90° angle from the base. next, we will use arduino nano's onboard Holes to prison it around the base structure. use 28mm wire and bend it at 24mm to prison it around the walls and finally solder the structure.

Step 10: Add the Screen

finally, its turn to add a Screen, for which we will need 4 wires of approximately 36mm length, which will be folded in parts according to Connecting Pads on Arduino, if you remember from Connections step, we have to Connect " Vcc to 5v : Gnd to Gnd : SDA to A4 : SCL to A5 " so simply bend your wire according to connection pad location.

( take your time don't rush here OLED is very delicate, i already broke one when it dropped during this project :P but don't worry just make sure you don't drop it )

once the pads are connected, solder the connector pins and it should easily hold up as shown in pictures attached to this step!

Step 11: Add "personal Touch"

since free-form electronics is not only about circuit, but its an ART in itself, just feel free to add your own touch to it, like i added Arms to make it look like a Robot, you can try crazy fits to make it like you like ( just don't ADD a tail to it, because if your pets wont like it, this might end up in their stomach XD ).

Step 12: Prevention Is Better Than Cure

we used copper wire for this build, which can be replaced with brass rods ( which isn't easily available in every country ) to make it weather resistant. but since we made it vulnerable to corrosion, let's add a Coat of "clear nail polish " to this entire structure, which will prevent the contact of copper to air and adds a little shine to our project.

Step 13: Support Our Work :)

if you followed up this post, and liked it, make sure to check out our other work on youtube, you can also support us for following Mission Critical on social media or becoming our patreon.

Patreon -

Twitter @ akshaymomaya1

Instagram @officialmissioncritical


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    11 months ago

    It would have been great to have seen a demo of it in use at the end! Neat build

    Great job I love the idea of Free-Forming it looks cool!


    Reply 1 year ago

    thank you :)


    1 year ago

    This isn't a "scale" but a "ruler".... title is confusing to me...


    Reply 1 year ago

    thanks for your correction, i also confuse about "scale" haha


    Reply 1 year ago

    sorry for that error, in our country, we call ruler as scale, i will keep that in mind for next time


    1 year ago

    thank you, and i guess that was the whole idea of experimenting with free form, hopefully everyone would like this technique