24 motor array

Using Arduino Project Guidance
4

Why not just this,http://www.ebay.com/itm/USB-UART-32-Channel-Servo-Motor-Controller-Driver-PWM-For-Arduino-Robot-A130-/251192458425?pt=LH_DefaultDomain_0&hash=item3a7c3cbcb9

Its a little expensive but it will do what you want it to.