Quote Originally Posted by fokus_1116 View Post
hi,
may i ask..if i wan to use battery to replace the power supply, what battery to recommend?
That is a difficult one to answer.
The VDIP requires 5 volts. Four re-chargeable "AA" batteries will give ~4.8 volts, close enough but for how long. Then if someone were to use regular batteries now there is ~6 volts present, not good, the MCU will "smoke".

Could use a 7805 regulator with a ~9 volt or higher battery pack but then you need to carry around a "brick" of batteries. And the 7805 requires a heat sink and is not the most efficient thing out there, reliable yes... LM317 could also be used but has some of the same problems.

You may want to use a switching regulator. Could have one that works with a battery input from 3 to 6 volts, then four "AA" batteries of any type will work. Depending on the circuit the efficiency can be very good.

Not knowing the load of the finished project, you may not know yet either, the best I caqn do is point you here
http://www.national.com/analog
Look at the "WEBENCH DESIGNER". Input your parameters and see what come up.

I have also hear some talk about off the shelf DC to DC converters.