This project is an open source Arduino Nano robotics project. It uses an L293D as a motor controller, and has inputs and outputs for an external 7-12V battery pack, as well as output pins for the motors.
There are two porto-pin areas available as separate 4x2 headers for use with extra sensors, radio antennas etc.
Smoothing capacitors can be added to both the power supply-input as well as the output to the motors.
The project has two versions. One where IN1 through IN4 is mapped directly to separate Arduino pins (D8-D13), and one using an inverter for the IN-pins on the L293D, enabling control of the motor directions using only two pins on the Arduino (freeing up two pins).
Along the sides of the PCB there are mounting holes for motor brackets and the standard "yellow-type" brushed DC motors that are abundant on eBay and Aliexpress. There are also six extra mounting holes designed to allow attachment of battery packs and a line sensor, etc.