hi, i would like to known some other way to build a power supply circuit without using regulator 7805 because i m using li-on battery 11.1v and using 2 set of voltage regulator circuit to powering my arduino bot with 5 servo motor attached. the problem is, my battery is running out in less than 7 minute and the servo motor regulator is very hot...
please feel free to give comment and suggestion 
thank you very much! i will check it out~
Hi,
What is the size of your battery and what is the current consumption of your servos?
Tom..... 
hi tom, i m using 2 360micro servo for the track wheel, 2 mini servo and 1 C55R servo motor for the arm. i m not very sure about the current consumption because i don't have any digital measurement tool with me... i m using 3 li-ion battery to get 11.1V , each battery 3.7V 2000mAh.
Hi,
Have you got a heatsink on the regulators, I would suggest before you go buying batteries you measure you current load.
Tom.....
yup, i did put a heat sink on each regulator. Actually trying to searching for li-po 25c 11.1V battery pack but unfortunately i didnt found any hobby kits shop around my collage... so i build my own battery pack by using portable battery bank's battery... here,i attach my arduino bot picture.
A DC-DC converter would be about twice as efficient as 7805's in dropping 11V to 5V,
but you would definitely need to know the peak current load as overloading a DC-DC
converter would simply cause it to cut-out.
that might be the point i'm looking for... But do u have a DC to DC converter circuit that can provide 3Amp ? cause by some reason, i avoid to buy the DC to DC converter online... hope i can build 1~
(sorry for my bad English)