Mini Paper USV PCB Upgrade v1.0 schematic twin using an ELEGOO MEGA 2560, L293D H-bridge, HC-SR04 ultrasonic sensor, SG90 servo header, LED indicators, buzzer, and dual 9V parallel battery input.Mini Paper USV PCB Upgrade v1.0 schematic twin using an ELEGOO MEGA 2560, L293D H-bridge, HC-SR04 ultrasonic sensor, SG90 servo header, LED indicators, buzzer, and dual 9V parallel battery input.