Hi Jason, could you use 3 or 4 AAs instead of a 9V (I guess
this is a PP3 type ?). Or is there a weight problem ? Maybe
AAA or AAAA ?

Losing almost 1/2 a 9V battery's voltage in a linear regulator like
the 7805 is very wasteful, and PP3s don't have a lot of capacity
to start with. A better linear choice that's common would be the
LP2950-5.0, and there are other low quiescent current ones. One
of the big drawbacks with a 7805 is that it consumes 8mA just
on its own. That's acceptable for a big battery or mains supply
but not for smaller batteries. Low quiescent current regulators
use only a fraction of the 7805, usually under 100uA (that's just
an 80th or better of 8mA)

The above probably won't solve your motor problem but it's
really worth thinking about

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