Analog Weighing Scale Using Load Cell

Overview

This project is an implementation of an analog weighing scale using a load cell and an amplification circuit with operational amplifiers (opamps). The goal is to measure weight with high accuracy and convert the load cell's analog signal into a readable format.

Table of Contents

• Introduction
• Components
• Circuit Diagram
• Working Principle
• Setup and Installation
• Usage

Introduction

This project demonstrates how to design and build an analog weighing scale using a load cell and an opamp-based amplification circuit. The load cell is a type of sensor that converts a force into an electrical signal. In this project, we use operational amplifiers to amplify the small electrical signals generated by the load cell for accurate weight measurement.

Components

• Load Cell
• lm324N Operational Amplifiers (Opamps)
• Resistors
• Capacitors
• Printed Circuit Board with Power supply (Designed by ourselves)
• ESP WROOM 32E Microcontroller
• Printed Circuit Board with Amplifiying part and the Microcontroller (Designed by ourselves)
• 230V AC to 12V AC Transformer
• Connecting Wires
• LCD Display

Schematic Design

Description of the circuit diagram:

• Outputs of the load cell is connected to the pcb.
• Then output difference voltage connects to inputs of instrumentation amplifier circuit.
• The amplified signal is directly connects to the ADC of the microcontroller.

PCB Layout

Amplifier and Microcontroller

Power Supply

Working Principle

1. Load Cell: The load cell deforms slightly when a force is applied, changing the resistance of strain gauges inside the cell.
2. Wheatstone Bridge: The load cell is wired in a Wheatstone bridge configuration, which outputs a small differential voltage proportional to the applied weight.
3. Amplification: The differential voltage from the load cell is very small, so it is amplified using an opamp-based differential amplifier circuit.For to be more precise and efficient we use a instrumentation amplifier circuit.
4. Output: The amplified signal can be read using an analog-to-digital converter (ADC), for this we use 12 bit ADC of the microcontroller.

Setup and Installation

1. Assemble the Circuit: Follow the provided circuit diagram to connect the load cell, opamps, and other components.
2. Power Up: Connect the power supply to the circuit.
3. Calibration: Calibrate the load cell and amplifier circuit using known weights to ensure accuracy.
4. Read Output: Connect the output to an ADC if using a microcontroller, or read the output directly on an analog meter.

Usage

1. Place Weight: Place the object to be weighed on the load cell.
2. Read Measurement: Observe the amplified signal on the analog meter or read the digital value from the microcontroller's display.

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