The ultrasonic transmitter includes two parts: an ultrasonic wave generating circuit and an ultrasonic wave transmitting control circuit. The ultrasonic wave probe (also called "ultrasonic transducer") selects CSB40T and can generate the ultrasonic wave by using the software generating method and the hardware generating method.
The former uses the software to generate 40kHz ultrasonic signal input to the drive through the output pin, driven by the driver to drive the probe to generate ultrasound. This method is characterized by full use of software, good flexibility, but the need to design a drive current above 100mA drive circuit.
The second method is the use of special ultrasound generating circuit or a common generating circuit to generate ultrasonic signals and directly drive the transducer to generate ultrasonic waves. The advantage of this approach is that it requires no driver circuitry, but lacks flexibility.
The design uses the first method to produce ultrasound, circuit design shown in Figure 2. 40kHz ultrasonic waves are generated using the 555-time base circuit. The oscillation frequency is calculated as f = 1.43 / ((R 9 + 2 · R 10) · C 5). The purpose of designing R 10 as an adjustable resistor is to adjust the signal frequency to match the transducer's 40 kHz natural frequency. In order to ensure 555-time base has sufficient driving ability, should adopt + 12V power. CNT ultrasonic emission control signal, controlled by the microcontroller.
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