3v to 5v Converter Schematic - You can use the Converter 3v to 5v circuit described here. We see that almost all of which are available today in addition to the microcontroller powered by a battery. But if we do not want a 5V in many cells in series …
Based on the integrated circuits Maxim IC MAX641, this dc to dc converter ic makes it possible to provide 5V from only two AA or AAA batteries. This differs from the typical linear regulator (and inefficient 7805) which requires minimal input 8V to ensure 5V to the output (besides too much heat!) the eight pin small integrated circuit, similar to the 555 form, no more and no less than the surge controller switch (or Step-Up Controller SMP) which only requires a few passive components to function properly.
The advantages of using this ic:
This IC generates almost no heat.
Consumes very low power to work.
Through sensing the output (feedback) allows efficient for regulate the voltage.
It has an output pin for LED low battery indicator
Integrated terminal 2 is set for the ground when the battery level falls. This pin can directly drive an LED or you can connect to the microcontroller pin to signal, for example, to show indication on the display.
Referency at http://powersupply88.com/converter-3v-to-5v.html