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Project Details

22 September, 2025 Published By: Dr. Bipul Krishna Saha

Design of Prototyping Lifecycle of SOS bangle

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Design of Prototyping Lifecycle of SOS bangle

The SOS Bangle project was designed as a wearable safety solution aimed at enabling quick emergency communication. The prototyping lifecycle explored multiple GSM modules to identify the most reliable hardware for sending SMS alerts when a trigger button is pressed. Through rigorous testing across different stages, the project evolved from early trials with SIM800L and SIM900A modules to a final stable solution with the A7670C module.

  • Stage 1 – SIM800L Module (Initial Development):
    • Hardware: Arduino Uno, SIM800L GSM module, M2M SIM (VI), 3.7V 3800mAh Li-ion battery, PCB antenna.
    • Objective: Send an SMS when a button is pressed.
    • Workflow: Trigger-based SMS using AT commands via TTL communication.
    • Challenge: Inconsistent network registration and reliability issues.
  • Stage 3 – SIM900A Module (Promising Start with Issues):
    • Hardware: Arduino Uno, SIM900A GSM module, 5V/2A power supply, VI SIM.
    • Objective: SMS sending on button press.
    • Result: Initially worked for 2–3 days with successful SMS delivery.
    • Issues: Later failed to register on network due to 2G fallback limitations, possible network congestion, overheating, or hardware fault.
  • Stage 4 – SIM A7670C Module (Final Reliable Solution):
    • Hardware: Arduino Uno / TTL, A7670C GSM module, 5V/2A power supply, VI & Airtel SIMs.
    • Objective: Continuous and reliable SMS sending on button press.
    • Result:
      • Stable SMS delivery across multiple networks.
      • No network registration issues (unlike SIM800L and SIM900A).
      • Reliable, repeated message sending with controlled delay.
      • Proved to be the final robust solution for the SOS Bangle prototype.

Objectives

  • Develop a wearable SOS device capable of sending SMS alerts instantly.
  • Test multiple GSM module solutions for reliability, network compatibility, and power efficiency.
  • Ensure stable and continuous operation under real-world conditions.
  • Provide women and vulnerable communities with an emergency communication tool.

Expected Outcomes

  • A functional prototype of an SOS Bangle with reliable GSM-based SMS alert capability.
  • Finalized hardware setup using A7670C GSM module for stability and performance.
  • Scalable design that can be mass-produced for community safety initiatives.
  • Enhanced personal security through quick emergency communication.