Design and Construction of a 5 KVA Automatic Voltage Regulator with Integrated Timer and GSM Control

Voltage fluctuation remains a major challenge affecting the reliability, performance, and lifespan of electrical equipment in Nigeria and many other developing nations. This study presents the design and construction of a 5 kVA automatic voltage regulator (AVR) integrated with a timer and GSM-based control system for remote monitoring and operation. The proposed system employs a microcontroller to detect variations in input voltage and automatically activate the appropriate relay combination to maintain a stable output voltage within the range of 220–240 V. A built-in timer introduces a short delay at startup to protect connected appliances from surge currents, while the GSM module provides remote ON/OFF control and real-time feedback through short message service (SMS). The hardware implementation incorporates a step-down transformer, voltage sensing circuit, relays, and protection devices, whereas the control software was developed in embedded C and tested using Proteus simulation before construction. Experimental results showed that the AVR provided reliable voltage regulation and fast dynamic response across different loading conditions, maintaining its output within a ±5 percent deviation from the nominal voltage. The inclusion of timer and GSM functionalities improved safety, usability, and monitoring efficiency. The system therefore offers a cost-effective and practical alternative to conventional stabilizers, especially for domestic and small industrial applications in regions affected by unstable power supply.