Sistema de medição de profundidade baseado em transdutor ultrassônico

Abstract

This work describes the development of an electronic device that can be shipped in an amphibious unmanned aerial vehicle (vehicle that was previously developed in Joint Project with the PTI) to measure depth of riverbeds using an ultrasonic sensor of 200 kHz by the Pulse-Echo technique. The device consists of the implementation of an excitation circuit that performs low amplitude pulse conversion generated by a microcontroller TM4C1294NCPDT for high amplitude pulses. The generation of the high voltage signal is given by means of a Boost converter, which converts the voltage of a 11,1 V battery to a voltage above 120 V. A Full-Bridge topology inverter circuit converts the DC voltage generated by the Boost converter into a square signal with a 200 kHz operating frequency, which will be conditioned by a resonant second-order low-pass filter for harmonic reduction. For the treatment of the received echo signal, an acquisition system was developed, consisting of a T/R Switch protection circuit with -0,714 dB losses for the coupling between the ultrasonic sensor and a variable gain amplification circuit that is controlled by the microcontroller, which allows the gain to be varied from 13,92 dB to 50,86 dB. The amplified signal passes through a peak detector circuit, in order that, by means of an internal comparator of the microcontroller, the decision is made whether an echo was or was not detected. The measured depth data is sent through a Wireless HC-12 RF transceiver for presentation on a computer through a platform developed in Visual Studio. In laboratory tests, which used a 46 x 86 cm barrel. The system showed ± 30 mm of measurement errors.