Motor Driver Board
SMARS needs a motor driver board (also called a shield) to provide additional power, and controller chips in a single convenient package. Motor driver boards are widely available.
The FunduMoto driver board is cheap and easy to buy online, however there isn’t a lot of documentation available for it. The best documentation available is at: http://rc.mired.org/2017/09/the-fundumoto-motor-shield.html
The FunduMoto driver is based on the L298P chip.
The board also has a small jumper labelled “OPT”, which when removed stops taking power from the Arduino and instead takes it from the shield power in. Make sure you have this jumper in the closed position if you want to use the ultrasonic sensor without using external power to the shield.
Ultrasonic sensor pinouts
The FunduMoto shield also has as convenient header for the ultrasonic sensor (HC-SR04)