Residual Current Monitor (PIC16F877A)

This project implements a simple residual current monitoring system using the PIC16F877A microcontroller. It monitors the analog input voltage (0–5 V) representing current sensed from a measurement circuit and activates an LED indicator when the value exceeds a threshold.

This version uses a potentiometer in simulation to adjust the sensed level for easy testing and calibration.

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Features

• Single-channel current level measurement using ADC (AN0)
• Adjustable trigger threshold in firmware
• Visual alert through an LED on RB0
• Runs in Proteus simulation environment
• Clean and beginner-friendly embedded C code (XC8 + MPLAB X)

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How It Works

1. The input voltage (0–5 V) is applied to the AN0 pin of PIC16F877A. In real use, this would come from a current transformer and conditioning circuit.

2. The ADC continuously samples this voltage.

3. If the reading exceeds a predefined 10-bit threshold value:

   • The LED on RB0 is turned on.

4. Below the threshold:

   • The LED remains off.

Threshold value can be tuned inside the firmware code.

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Hardware / Simulation Setup

Proteus Schematic (Potentiometer Version)

• Potentiometer:

  • Left → +5 V
  • Right → GND
  • Middle (wiper) → RA0/AN0 (Pin 2)

• LED output:

  • RB0 (Pin 33) → 330 Ω resistor → LED → GND

• Power:

  • Pin 11 (VDD) and Pin 32 → +5 V
  • Pin 12 (VSS) and Pin 31 → GND

• Clock:

  • No crystal required in schematic
  • Set clock frequency to 4 MHz in PIC properties

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Firmware

Located in: firmware/main.c

Written in XC8 for PIC16F877A.

Key snippet:

unsigned int v = adc_read_ch0();
if(v > THRESHOLD_ADC)
    RB0 = 1;
else
    RB0 = 0;

Adjust this constant to change sensitivity:

#define THRESHOLD_ADC 512   // Half-scale of ADC (≈2.5V)

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Project Structure

Residual-Current-Monitor-PIC/
├─ firmware/
│  └─ main.c
├─ proteus/
│  └─ schematic.pdsprj  (to be added)
└─ README.md

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Future Enhancements

Planned improvements include:

• Dual-channel measurement (Live vs Neutral)
• Leakage detection by comparing two ADC channels
• Relay trip output for protection
• UART or LCD display of readings
• Proper calibration using real CT sensors
• PCB design for hardware deployment
• Safety isolation for mains operation

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Disclaimer

This project is intended for learning and simulation purposes only. It is not a certified Residual Current Device and must not be used for real mains protection without proper electrical safety design and compliance to standards.

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