Hello Sougata,

I have a similar requirement, but without the LCD. Same 6V operation and a Piezo buzzer.

Its basically a code lock operating on 6V. A couple of flashing LED, Sounder (piezo) and a Solenoid.

I have a design before me which does not use even a series diode to drop the voltage, So I presume , the PIC can take that, till the Alkaline battery drops down to safer level on its own. Seeing this , I feel a series diode would be good.

I used a GP PNP transistor with zener at its base to regulate the voltage. Don't know if that's the right way.

Any help ?