Project Overview

This project involves designing custom hardware for an ultrasonic distance measurement system from scratch. The system will measure distances from 2cm to 400cm with ±1cm accuracy using ultrasonic pulse-echo time-of-flight measurement.

FOR FULL PROJECT:

https://electronicsworkshops.com/flood-detection-and-warning-system-using-lora-and-arduino/

Introduction

Distance measurement is a key requirement in many electronic and automotive applications such as parking assistance systems, obstacle detection, robotics, industrial automation, and smart devices. Ultrasonic sensors are widely used for this purpose because they are low cost, reliable, and work in various lighting conditions.

Most projects use ready-made ultrasonic modules. However, this project focuses on designing our own ultrasonic sensor hardware from scratch, including signal generation, signal reception, processing, and distance calculation. This approach helps in understanding the core electronics, timing principles, and hardware design challenges involved in ultrasonic sensing.

Working Principle of Ultrasonic Distance Measurement

Ultrasonic sensors work on the echo principle, similar to how bats navigate.

Basic Concept:

The transmitter sends a high-frequency ultrasonic pulse (typically 40 kHz).

The sound wave travels through air and hits an object.

The wave reflects back and is received by the receiver.

The time taken for the pulse to return is measured.

Distance is calculated using the speed of sound.

Distance Formula:

Distance=Time×Speed of Sound2\text{Distance} = \frac{\text{Time} \times \text{Speed of Sound}}{2}Distance=2Time×Speed of Sound​

Speed of sound ≈ 343 m/s at 25°C

Division by 2 is required because the pulse travels to the object and back

Working Principle

Signal Flow:

Oscillator (U74 + G93-3) → generates 40kHz signal

Driver ICs (U78, U79) → amplify current capability

Transformer (T1074) → steps voltage up to 100-200Vpp

Matching network (L1, capacitors) → tunes to transducer resonance

Ultrasonic Transmitter → emits 40kHz sound waves

The receiving transducer converts reflected sound waves into a weak electrical signal.

The signal is amplified using a high-gain amplifier.

Noise and unwanted frequencies are removed using a band-pass filter.

Circuit Diagram

This custom ultrasonic sensor circuit takes the very weak echo signal from the ultrasonic receiver, AC-couples it and amplifies it in two stages using an MCP602 dual op-amp biased at mid-supply so it can work from a single power source; the amplified ultrasonic signal is then DC-blocked and rectified using diodes to convert it into a detectable pulse, which drives an NPN transistor acting as a switch to produce a clean logic-level output, making the circuit suitable for reliably detecting ultrasonic echoes and interfacing directly with a microcontroller or timing circuit for distance measurement.

This circuit is the ultrasonic transmitter and communication interface section: the ultrasonic transducer A1 generates ultrasonic pulses driven from the control signals, while power enters through connector J1 and is filtered by a ferrite bead (FB1), protection diode (D3), and decoupling capacitors to provide clean VCC; the MAX232 (U2) converts logic-level TX/RX signals (T1IN, T2IN, R1IN, R2IN) to proper RS-232 voltage levels using its charge-pump capacitors (C7–C11), enabling reliable communication between a microcontroller and external systems (PC or tester), while the surrounding capacitors ensure stable voltage generation and noise-free operation for accurate ultrasonic transmission and data exchange.

PCB

3D

Advantages of Custom Hardware Design

Better understanding of ultrasonic technology

Flexible design for specific applications

Cost optimization in mass production

Improved reliability and tuning

FOR FULL PROJECT:

https://electronicsworkshops.com/flood-detection-and-warning-system-using-lora-and-arduino/

Conclusion

This project successfully explains the design and development of custom ultrasonic distance measurement hardware. By designing the transmitter, receiver, and signal processing circuits independently, we gain deep insight into ultrasonic sensing technology. The system accurately measures distance using the time-of-flight method and can be further enhanced for automotive and industrial applications.