The paired regulator and controller
Building one of my robots with 6 volt motors challenged me to come up with the solution myself. What I built is a high current 7805 circuit that powers 4 Toshiba TA8050P motor driver chips. The regulator was built on an IC proto board with a TIP120 doing the heavy lifting. The result is a conservative 5 amps of output current. This should happily drive the four DC motors and the Arduino as well.
Another view of the paired devices
I built the controller on a mated pair of IC proto boards, using female 0.1 snip-off headers as 7 pin sockets for the TA8050Ps. I used a 301 ohm resistor and a 3mm red LED as a power indicator. I also added a couple of 10uf caps to help level the voltage and prevent ripple. Both the regulator and the controller are very straight forward, letting the pair of chips do the complex work and letting me just Lego them together.