This is one of the most cost effective (cheap) and simple emergency light circuit.
This is an Automatic Emergency Lamp with Day Light Sensing, means it
senses darkness/night and turns ON automatically. Similarly it senses
day light and turns OFF automatically.
A simple Emergency Lamp which does not
require any special equipment; even a multimeter to assemble and use.
Any individual who can do a good quality soldering must be able to build
this circuit successfully. This can be easily accommodated in the
defunct two 6 watt tube National Emergency Lamp or any PL tube type
emergency lamp. The difference will be in the working; it will work non
stop for more than 8 hours. Deep discharge is taken care by the LED
characteristic and over charge protection is taken care by the fixed
voltage regulator.This uses a simple 3Pin fixed regulator which has a
built in current limiting circuit. The only required adjustment is the
preset which has to be set to ensure the LEDs just light up (it should
be left at that position). The 5mm LDR is just mounted on top of the
emergency light as shown in the photograph. LDR is used to avoid it
lighting up during day time or when the room lights are ON. 2 LEDs are
used in series; the dropping resistance is avoided and 2 LEDs light up
with current that is required for a single LED, by which energy is
saved to a great extent.
Note: This particular circuit has been kept so
simple for people who has limited access to components or in other words
this is an emergency light that you can build with minimum components.