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
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.
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. In addition to circuit
diagram, He has shared photographs of the prototype he made in National
emergency light and a PCB design.