Browsing by Author "Saifullah, Khalid"

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Design and Implementation of Smart Portable Safety Alert System for Vulnerable Individuals
(Daffodil International University, 2025-11-24) Mazumder, Manos; Ahmed, Riaj; Masrur, Asif Al; Saifullah, Khalid
Safety is a basic need, but not everyone has equal access to it, especially vulnerable groups like the elderly, children, people with disabilities, and women. This paper introduces a Smart Portable Safety Alert System designed to offer immediate support in emergency situations for these persons. The system was built using an Arduino UNO integrated with a SIM808 GSM/GPS module and also an additional GPS tracker for better accuracy to detect the user’s location and send an alert message or make a phone call via GSM communication by pressing the emergency switch. This prototype is powered by a rechargeable battery and was programmed through embedded C, ensuring fast response and low power consumption. The system can transmit location data accurately and deliver SMS/call alerts promptly within a few seconds, as confirmed by experimental testing. The system is compact, portable, economical, and dependable. These features make it suitable as personal safety for vulnerable persons during critical conditions.
Firehawk: an autonomous firefighting drone with fire-extinguishing ball release mechanism
(BRAC University, 2025-12) Alvi, Atair Rahman; Hamim, Ifrana; Adnan, Faraaz; Chowdhury, Misbahul Azim; Saifullah, Khalid; Azad, AKM Abdul Malek; Avash, Ihteyaz Aqaeed
This project presents a significant advancement in the field of autonomous emergency response systems by addressing the critical challenges associated with rapid fire detection and suppression. The system integrates a combination of environmental sensors, including flame, smoke, and temperature modules, to accurately identify potential fire hazards in real time. Leveraging modern UAV technology, the autonomous drone is equipped with a precision-controlled release mechanism capable of deploying a fire-extinguishing ball directly onto the fire source, enabling quick and targeted suppression without endangering human responders.Using advanced flight control algorithms, GPS navigation, and wireless telemetry communication, the drone ensures seamless data acquisition, autonomous decision-making, and mission execution. Real-time monitoring and alerting allow operators or emergency personnel to receive immediate updates on fire occurrences, improving situational awareness and enabling faster intervention. The system enhances firefighting efficiency by accessing dangerous or unreachable areas, reducing response time, and minimizing property damage. Overall, this project significantly strengthens the capacity for early-stage fire management through intelligent aerial intervention. By combining autonomous navigation, real-time fire detection, and automated suppression, the proposed solution contributes to safer communities, improved emergency response strategies, and a more resilient firefighting infrastructure.
New efficient AC-DC converters and their applications
(Department of Electrical and Electronic Engineering, Islamic University of Technology, 2017-11-15) Saifullah, Khalid; Hysam, Md. Abdullah Al; Haque, Md. Zihad Ul; Asif, Sakif
AC-DC converters are mostly used as power supplies for microelectronic systems, battery chargers, wind energy applications, electric appliances in household and dc motor drives. Switched-capacitor (SC) network based converters can be good solution to the challenges of 21st century having high voltage conversion ratio and low EMI emissions. The application of this type of converters is in microprocessor based systems where the line voltage requires a steep step down to 3V or even less in order to drive integrated circuits (ICs). In this paper, a new high step down bridgeless single switch AC-DC converter with switched capacitor is proposed. The absence of transformer as well as bridge rectifier reduce the components count, size and cost of the converter. Unlike the existing converters, this proposed buck boost converter is able to achieve simple control structure with single switch, high efficiency, low total harmonic distortion (THD) and high input power factor. Power supplies for microelectronic systems, battery chargers, wind energy applications, electric appliances in the household and dc motor drives require AC-DC converters. The proposed bridgeless Cuk PFC converter in this paper is featured with common ground, transformerless structure, and clear energy delivery process. The absence of bridge rectifiers, transformer and the presence of only two semiconductor switches in the current flowing path during each switching cycle result in less conduction losses and improved thermal management, reducing components count, size and cost of the converter compared to the conventional SEPIC and Cuk PFC converters. Moreover, the presence of two power switches for different half cycles leads to less stress on the power switch. Unlike the existing converters, this proposed bridgeless Cuk PFC converter is able to achieve simple control structure with high efficiency, low total harmonic distortion (THD) and high input power factor. This letter describes a new application of single-ended primary converter (SEPIC) and Cuk converter for dc bipolar net-work. A dc–dc converter configuration based on a combination of both converters is proposed. In the resulting topology, the switching node is shared by the SEPIC and Cuk converter since they have the same instantaneous duty cycle. The main advantage of this topology is that synchronization of various switches is not required, and control terminal is connected to ground which simplifies the design of the gate drive. On the other hand, this configuration allows the connection of renewable energy sources to microgrids (MG)-type bipolar dc link and to cover the current needs of new distributed generation units with efficient, economical, and easy way. To verify its performance, a prototype was designed. Experimental results show as this combination of two converter topologies with appropriated modulation schemes are adequate to use in dc MG.