Referência Bibliográfica

  http://www.eletronica.com/sensor-de-estacionamento-para-veiculos/

  https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQf9pXcorJ7aIMm4P9moYWGtQhBhkN6t6gTiHF_GeMbwPGbMgrnkDQlRIe_b3PCT1MRNURIdr1T6pWCkJ37sJ6OENFpgLWlCAPmu9nqTaNeH8t7KAXQ6h6QQSVSsxFCq-GQ3bNeyCGrYD9/s400/car01.jpg

  http://www.novaeletronica.net/tutoriais/555/555a.htm

      http://www.engineersgarage.com/electronic-components/lm324n-datasheet