This paper describes a model of a smart street
light that can work autonomously, save energy and can be
seamlessly integrated with the existing grid. The street light
incorporates a Light Emitting Diode array and an ARM
Cortex M0 based microcontroller, both of which are
powered by a combination of a solar panel and battery pack.
The microcontroller executes an astronomical time switch
based estimation algorithm to determine the sunrise and
sunset time daily. This is done using the Real Time Clock
running on the controller along with the hard coded
coordinates and time zone of any given location. Upon
evaluation of the sun times, the controller can routinely
regulate the lamp at sunrise and sunset. The algorithm
operates with an accuracy of up to 10 seconds in its
estimation of sun times. The controller also monitors the
voltage from the battery at sunset and switches to mains to
power up the LED array in case power is not enough. A coin
cell is also connected to the controller to ensure RTC keeps
on running in the scenario that battery is completely
discharged and there is no power from the mains. The
results conclude that the use of such a technology would
provide high energy efficiency, increases the operating life
and also proves to be cost effective as compared to prevalent
lamp technologies. Analysis is performed using HOMER, a
microgrid simulation software. The boundary conditions are
set for Indian scenarios; however the result applies to many
geographical locations.