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Embedded Systems

Digital Thermometer with PIC

PIC16F877A-based temperature monitoring system with ADC reading, UART logging, and overheat alert mechanism

PIC16F877A Embedded C LM35 ADC UART MPLAB X

Project Overview

This embedded systems project implements a complete temperature monitoring solution using the PIC16F877A microcontroller and LM35 temperature sensor. The system provides accurate temperature readings, real-time UART data logging, and an intelligent overheat alert mechanism for safety demonstrations.

The project showcases fundamental embedded systems concepts including ADC configuration, sensor interfacing, and communication protocols, making it ideal for industrial monitoring and safety applications.

Key Features

🌡️

Accurate Sensing

LM35 sensor provides precise temperature measurements with 10mV/°C linear scale

⚙️

ADC Processing

10-bit ADC resolution for accurate analog-to-digital conversion of temperature data

📡

UART Logging

Real-time serial communication for continuous temperature monitoring and data logging

🚨

Alert System

Configurable threshold-based overheat detection with visual and audible alerts

Hardware Architecture

Core Components

  • Microcontroller: PIC16F877A (40-pin DIP)
  • Sensor: LM35 precision temperature sensor
  • Display: 16x2 LCD for real-time temperature display
  • Alerts: LED indicator and buzzer for overheat warnings
  • Communication: MAX232 for UART level conversion

Circuit Design

  • ADC Channel 0 configured for LM35 input (0-5V range)
  • Crystal oscillator: 20MHz for precise timing
  • LCD connected to PORTD with control signals on PORTB
  • Alert outputs on dedicated GPIO pins with current limiting resistors

Software Implementation

Embedded C Programming

  • ADC initialization and configuration for continuous conversion
  • Temperature calculation algorithm: Temp = (ADC_Value * 5000) / (1024 * 10)
  • LCD driver functions for displaying temperature in Celsius and Fahrenheit
  • UART communication at 9600 baud for PC interface
  • Interrupt-driven alert system for threshold monitoring

Development Environment

  • MPLAB X IDE for code development and debugging
  • XC8 compiler for efficient code generation
  • Proteus simulation for circuit validation
  • PICkit 3 programmer for device flashing

System Specifications

±0.5°C
Accuracy
1 sec
Update Rate
-55 to 150°C
Range

Key Learnings

ADC Configuration

Mastered ADC module configuration including acquisition time, conversion clock selection, and reference voltage settings for optimal sensor reading accuracy.

Sensor Interfacing

Learned proper sensor calibration techniques and signal conditioning to minimize noise and ensure stable temperature readings.

Real-time Processing

Implemented efficient interrupt-driven architecture to handle simultaneous display updates, UART transmission, and alert monitoring without delays.

Applications

  • Industrial process monitoring and control
  • HVAC system temperature regulation
  • Laboratory equipment monitoring
  • Food storage temperature tracking
  • Environmental monitoring stations
  • Safety demonstrations in educational settings