Project Hub/Test & Measurement Instrumentation/Multimeters, Voltmeters & Ammeters/Measure Difficult Angles With This Digital Protractor

Beginner

ARDUINO

₹500 – ₹1,500

3 – 6 Hours

Measure Difficult Angles With This Digital Protractor

Build a digital protractor that calculates and measures complex angles by converting stepper motor rotation steps into precise angular measurements.

Originally published by Ashwini Sinha on ElectronicsForU

View original tutorial

How It Works

The Digital Protractor is built around an Arduino Pro Mini microcontroller, which acts as the central processing unit for measuring and displaying angles. When you physically manipulate the device, a 28BYJ-48 unipolar stepper motor rotates in response to the movement. Because stepper motors move in fixed, discrete steps, tracking the number of steps taken allows the system to calculate precise angular displacement. The ULN2003A motor driver module sits between the Arduino Pro Mini and the stepper motor, providing the necessary current amplification and switching logic to control the motor coils accurately since the microcontroller pins cannot supply enough direct current. User interaction is handled by two pushbutton switches, which can be used to reset the zero angle, calibrate the device, or change operational modes. As the measurements are calculated, the I2C OLED display receives data from the Arduino and visually presents the precise angle to the user in real time. The entire circuit is powered by a portable 5V battery connected via jumper wires, making the device completely self-contained for field measurements. Software uploaded via the Arduino IDE utilizes a specialized stepper motor library to translate mechanical rotation into reliable angular readouts.

Why Build This

Ideal for school physics and engineering design projects requiring precise measurement instrumentation.

Useful for practical DIY home improvement and woodworking tasks where awkward angles must be calculated.

Provides a hands-on introduction to electromechanical feedback systems by combining mechanical motion with digital microcontrollers.

Real-World Application

Construction, architectural surveying, DIY home improvement, and precision mechanical layout where measuring awkward structural angles is required.

Skills You'll Learn

Stepper motor control

I2C communication protocol

digital input handling with pushbuttons

microcontroller programming

display interfacing

Safety Precautions

Ensure correct polarity when connecting the 5V power supply and common ground to avoid short-circuiting components.

Technology Tags

STEPPER MOTOR

ULN2003A

OLED DISPLAY

PUSHBUTTONS

ARDUINO IDE

C++

ANGLE MEASUREMENT

Frequently Asked Questions

Why is a ULN2003A motor driver module needed instead of connecting the stepper motor directly to the Arduino Pro Mini?

The Arduino Pro Mini digital pins cannot supply enough electrical current to drive the motor coils directly; the ULN2003A acts as an amplifier to safely handle the motor's power requirements.

How does the device know what angle it is measuring?

The system counts the precise number of steps the 28BYJ-48 unipolar stepper motor rotates when moved, converting those steps into degrees of angular displacement.

What is the purpose of the I2C interface on the OLED display?

The I2C protocol allows the OLED display to communicate with the Arduino Pro Mini using only two data wires (plus power and ground), freeing up other pins for the motor driver and pushbuttons.