Ultrasonic Signal Implementation in Arduino-Based Obstacle Robot Control System Hanifudin Sukri, Deni Tri Laksono, Dedi Tri Laksono and Miftachul Ulum E3S Web Conf., 328 (2021) 02008 Published online: 06 December 2021 DOI: 10.1051/e3sconf/202132802008