Project Hub /Test & Measurement Instrumentation/Sensors & Signal Measurement Tools/How to Make a Portable Ultrasonic Digital Ruler using ATtiny85

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How to Make a Portable Ultrasonic Digital Ruler using ATtiny85

Build a compact, portable digital measuring device using an ATtiny85 microcontroller, HC-SR04 ultrasonic sensor, and an I2C OLED display on a custom PCB.

Originally published on CircuitDigest

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

Ultrasonic Sensor Module HC-SR04 Rs. 89.00
0.96 Inch I2C/IIC 4pin OLED Display Module White Rs. 349.00
LM2596 Step Down DC-DC Buck Converter Rs. 99.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

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How It Works

The Portable Ultrasonic Digital Ruler operates by coordinating several key hardware components powered by a 9V battery. Because the HC-SR04 ultrasonic sensor and I2C OLED display require a stable 5V supply, the AMS1117 5V voltage regulator steps down the incoming 9V battery voltage to a safe, regulated level for the logic circuitry. A 10 uF capacitor is placed across the power rails to help filter voltage ripples and stabilize the power supply during transient current spikes. At the core of the system is the ATtiny85 microcontroller, programmed using the Arduino IDE with the TinyWireM and TinyOzOLED libraries to communicate with the display and manage sensor timing. The ATtiny85 triggers the HC-SR04 ultrasonic sensor to emit a high-frequency sound wave, then measures the time it takes for the echo to return after bouncing off a target surface. By calculating the elapsed time of flight, the microcontroller computes the exact distance to the object. Finally, this calculated distance value is transmitted via the I2C protocol to the OLED display module, providing the user with a real-time digital readout. The entire circuit is integrated onto a custom PCB for a compact, professional layout.

Why Build This

Design and deploy a custom PCB integrating power regulation, sensor interfacing, and low-pin-count microcontroller programming.

Implement I2C communication protocols on a resource-constrained ATtiny85 architecture using specialized libraries.

Develop practical contactless measurement systems applicable to undergraduate robotics, automation, and assistive technology engineering.

Real-World Application

Distance measurement, robotic obstacle avoidance, contactless automated measurement tools, and assistive technology aids like blind walking sticks.

Skills You'll Learn

Microcontroller firmware development

I2C serial communication

ultrasonic time-of-flight distance calculation

linear voltage regulation

custom PCB design and integration

Safety Precautions

No specific precautions noted for this build — always follow general electronics safety practices.

Technology Tags

ATTINY85

HC-SR04

ULTRASONIC SENSOR

OLED DISPLAY

PCB DESIGN

I2C

ARDUINO IDE

C++

EMBEDDED SYSTEMS

Frequently Asked Questions

Can I program the ATtiny85 directly via USB without a programmer?

No, the ATtiny85 lacks native USB communication hardware, so you will need an external programmer or an Arduino configured as an ISP to upload your code through the Arduino IDE.

Why is an AMS1117 5V voltage regulator necessary in this circuit?

The 9V battery provides a voltage higher than the maximum rating of the ATtiny85, HC-SR04, and OLED display, so the regulator safely steps it down to a stable 5V to protect the components.

Why use the TinyWireM library instead of the standard Wire library?

The ATtiny85 does not have built-in hardware TWI/I2C pins in the same way standard Arduino boards do, so TinyWireM provides a specialized USI-based implementation for I2C communication on the ATtiny.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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