The article describes a very simple homemade emergency light
circuit that can be used during power failures and outdoors where any other
source of power might be unavailable. The circuit uses LEDs instead of
incandescent lamp, thus making the unit very power efficient and brighter with
its light output. Moreover, the circuit employs a very innovative concept
especially devised by me which further enhances the economical feature of the
unit.
We know that LEDs require a certain fixed forward voltage
drop to become illuminated and it is at this rating when the LED is at it’s
best, that is voltages which is around its forward voltage drop facilitates
the device to operate in the most efficient way.
As this voltage is increased,
the LED starts drawing more current, rather dissipating extra current by
getting heated up itself and also through the resistor which also gets heated
up in the process of limiting the extra current.
If we could maintain a voltage around an LED near to its
rated forward voltage, we could use it more efficiently. That’s exactly what I
have tried to fix in the circuit.
Since the battery used here is a 6 volt battery, means this
source is a bit higher than the forward voltage of the LEDs used here, which
amounts to 3.5 volts. The extra 2.5 volts rise can cause considerable
dissipation and loss of power through heat generation.
Therefore I employed a few diodes in series with the supply
and made sure that initially when the battery is fully charged; three diodes are
effectively switched so as to drop the excess 2.5 volts across the white LEDs (because each diode drop 0.6 volts across itself).
Now as the voltage of the battery drops, the diodes series are reduced to two and
subsequently to one making sure only the desired amount of voltage reaches
the LED bank.
In this way the proposed emergency lamp circuit is made
highly efficient with its current consumption, and it provides backup for a much
longer period of time than what it would do with ordinary connections. sourced by : homemade
