LED Based Automatic Emergency Light
Here
is a white LED based low cost emergency light that offers high
brightness, automatic activation, automatic charging with the use of
cheap components. The circuit is very simple in construction and we can
use the emergency light up to 6++ hours on battery feed.
As we know the power supply have been regulated by the the LM317 IC and produces a 7 volts output for charging the battery. when the battery gets charged to 6.8V the zenar ZD1 conducts and the IC1 output get shorted to ground through T1 so it stops charging. The transistor BD140 drives the out put LED's.
Assemble the circuit on a general-purpose PCB and enclose in a cabinet with enough space for battery and switches. Mount the LED's on the cabinet such that they light up the room. A hole in the cabinet should be drilled to connect 230V AC input for the primary of the transformer.
Note: it is better to connect a proper size heat sink to BD 140 and LM317. The output of LM 317
must be configured to 7v by adjusting the potentiometer.