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Automatic Emergency Light Circuit

Automatic Emergency Light CircuitAutomatic Emergency Light Circuit

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 Automatic Emergency Light Circuit comprises two sections: charger ability accumulation and LED driver.The charger ability accumulation area is built about 3-terminal adjustable regulator (IC1) LM317, while the LED disciplinarian area is congenital about transistor BD140(T2). In the charger ability accumulation section, ascribe AC mains is stepped bottomward by agent to bear 9V, 500mA to the arch rectifier, which comprises diodes (IN4007x4). Filter capacitor (25v/1000uf)eliminates ripples.

Able DC voltage is fed to ascribe pin 3 of IC1 and provides charging accepted through diode IN4007(D5) and attached resistor (16ohm)R16. By adjusting preset 2.2K(VR1), the achievement voltage can be adapted to bear the appropriate charging current. Back the array gets answerable to 6.8V, zener diode conducts and charging accepted from regulator (IC1) finds a aisle through transistor BC547(T1) to arena and it stops charging of the battery. The LED disciplinarian area uses a absolute of twelve 10mm white LEDs. All the LEDs are affiliated in alongside with a 100-ohm resistor in alternation with each. The common-anode alliance of all the twelve LEDs is affiliated to the beneficiary of pnp transistor T2 and the emitter of transistor T2 is anon affiliated to the absolute terminal of 6V battery.

The able DC voltage, produced at the cathode alliance of Bridge(Diodes), is fed to the abject of transistor T2 through a 1k resistor. Back mains ability is available, the abject of transistor T2 charcoal aerial and T2 does not conduct. Thus LEDs are off. On the added hand, back mains fails, the abject of transistor T2 becomes low and it conducts. This makes all the LEDs (LED1 through LED12) glow. The mains ability supply, back available, accuse the array and keeps the LEDs off as transistor T2 charcoal cut-off. During mains failure, the charging area stops alive and the array accumulation makes the LEDs glow.

Assemble the ambit on a general-purpose PCB and enclose in a chiffonier with abundant amplitude for array and switches. Mount the LEDs on the chiffonier such that they ablaze up the room. A aperture in the chiffonier should be accomplished to affix 230V AC ascribe for the primary of the transformer. I accept activated the ambit with twelve 10mm white LEDs.You can use added LEDs provided the absolute accepted burning does not beat 1.5A. Disciplinarian transistor T2 can bear up to 1.5A with able heat-sink arrangement.