Buy Ultrasonic — Transducer

Available at Adafruit Industries , this ubiquitous sensor is ideal for distance measurement (2cm to 400cm) in robotics and interactive art. A02YYUW Waterproof Ultrasonic Sensor DFRobot& more Go to product viewer dialog for this item.

HC-SR04 Ultrasonic Sonar Distance Sensor + 2 x 10K resistors Adafruit Industries Go to product viewer dialog for this item. buy ultrasonic transducer

A high-power converter for plastic welding applications, found on eBay. Available at Adafruit Industries , this ubiquitous sensor

Industrial-grade transducers are designed for high-power continuous or pulse operations, such as ultrasonic cleaning tanks or plastic welding machines. Ultrasonic Transducer 60W 40kHz Go to product viewer dialog for this item. Available at Adafruit Industries

A complete learning kit for beginners available at RobotShop.com , including an Uno R3 microcontroller and lesson guides.