Automatic Low-Power Emergancy Light circuit

This circuit features a white LED-based emergency light that provides several benefits. It is exceptionally bright due to the incorporation of white LEDs. The light activates automatically when the mains supply is interrupted and deactivates when mains power is restored. Additionally, it includes a built-in battery charger that ceases operation automatically once the battery reaches full charge. The power supply section for the charger is designed using the 3-terminal adjustable regulator IC LM317 (IC1), while the LED driver section utilizes the BD140 transistor (Q2).

The emergency light circuit is designed to ensure reliable illumination during power outages. The white LEDs are selected for their high luminous efficacy, providing bright and efficient lighting. The automatic activation feature is achieved through a relay or a similar switching mechanism that detects the absence of mains voltage. When the mains supply fails, the circuit engages the LED driver, allowing the white LEDs to illuminate the area.

The battery charger circuit, based on the LM317, is configured to maintain optimal charging conditions for the battery, which is typically a rechargeable lead-acid or lithium-ion type. The LM317 serves as a voltage regulator, ensuring that the battery receives a consistent voltage level for charging. The automatic shut-off feature is implemented using a voltage sensing mechanism that detects when the battery is fully charged, thereby preventing overcharging and extending the battery's lifespan.

The LED driver, constructed with the BD140 transistor, efficiently manages the current flow to the LEDs. This configuration allows for a stable and controlled output, ensuring that the LEDs operate within their specified parameters. The circuit may also include protective components such as diodes to prevent reverse polarity and capacitors for smoothing voltage fluctuations.

Overall, this emergency light circuit is a practical solution for providing illumination during power failures, combining energy-efficient lighting with an intelligent charging system for enhanced performance and reliability.Here is a white-LED-based emergency light that offers the following advantages. 1-It is highly bright due to the use of white LEDs. 2-The light turns on automatically when mains supply fails, and turns off when mains power resumes. 3-It has its own battery charger. When the battery is fully charged, charging stops automatically. The charger power supply section is built around 3-terminal adjustable regulator IC LM317 (IC1), while the LED driver section is built around transistor BD140 (Q2).. 🔗 External reference