i am making a battery operated project in which i want to put arduino in sleep mode but the problem is that the battery i use is 12v so i need to regulate that 12v down to 5 v either through a buck converter or a linear voltage regulator both of which will consume current of the order of milliamp can someone suggest me something to reduce this current or convert 12v to 5v efficiently
I don't know the answer but if you edit your Original Post and create a Title that summarizes your problem you are much more likely to catch the attention of someone who does know. What about "Suggestions for efficient 12v to 5v converter"
I once bought a commercial piece of test equipment that had a 9V battery and a PIC running off 5V. The power button was a soft switch that put the PIC into sleep mode. Of course, putting the PIC into sleep mode didn't stop the linear regulator they used flattening the battery. "Idiots" comes to mind.
I don't know the answer but if I were trying to do this and it were essential that the Arduino did not power down completely then I think I'd include a separate battery to power the Arduino in sleep mode and completely disconnect the 12V battery using a MOSFET (actually 2 MOSFETS I think). I'd probably use a rechargeable battery and charge it from the 12V supply when it was available.
Do you really need sleep mode? The later version of the tester I mentioned had a button you press to power it, releasing the button completely disconnects the battery.
Without knowing more about what you are doing it's difficult to be more helpful.
What is the total power consumption of your project?
This matters a lot.
Using a 12V battery is never really efficient.
Maybe power your Arduino from a 3.7V LiPo (use a 3.3V Pro Mini - remember to remove the LEDs for significant power savings) which in turn can get charged from the 12V battery?
i am thinking of doing this
Excellent selection of Pololu - Step-Down Voltage Regulators.
The problem is that a regulator that is highly efficient at significant loads, may not have the very low idle (quiescent) current that you’d like to have for a sleeping avr.
(Nevertheless, pololu would be my first choice as well.)
If you have a 10A load, even if used only occasionally for a short time, the quiescent current or even an awake Arduino won't matter much for the total battery life.