ultrasonic speaker

The 555 chip is used to generate a 40kHz square wave signal. The 3.5mm audio input signal is modulated by the duty cycle of the square wave after passing through a high-pass filter. After passing through the L293DNE driver, it drives the ultrasonic transducer to produce sound.

12VDC power supply, power supply for L293D; regulated to 5v by LM1117-5 to power the 555 chip and provide signal voltage reference for L293D 

Using a 40-16T ultrasonic transmitter, a single operating current is about 3mA, and L293DNE supports a maximum output of 600mA per channel.

According to the actual measurement, the sound can be slightly heard with more than 8 speakers, and more than 30 speakers are needed to achieve better results, which can reflect good directional propagation characteristics.

Notice:

(1) The calculated value of the C3 capacitor of the 555 chip should be 150pF, but due to actual errors, it is more appropriate to use a 100pF ceramic capacitor in actual measurements

(2) 1117 needs a radiator, but I couldn’t find it on Lichuang.