Hardware Reference
In-Depth Information
Figure 11-14:
9V battery pack
9V batteries are expensive, so some people prefer to use a AA battery pack.
An average AA battery has a nominal voltage of 1.5V. Hence, it's fairly common
to put four of these in series to generate about 6V total. Connecting four AA bat-
teries to the Vin pin or the barrel jack input of the Arduino sends power through
the voltage regulator, which has a small “dropout” voltage. (A dropout voltage
is the minimum voltage that must exist between the input and output voltages.)
On the Arduino, the 5V regulator has a dropout of approximately 1V (though
this varies with temperature and current consumption). The input from a AA
battery pack (with four batteries) is generally around 5.5V. With a 1V drop, you
can generally expect that the Arduino logic will be operating around 4.5V. The
ATMega is rated to run at this voltage (it can actually run all the way down to
1.8V), but you should be aware that all your logic will be operating at a slightly
lower voltage than when you are on USB.
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