I am building an ultrasonic flow sensor, based on piezoelectric actuators from cheap HR-SR04 modules. I need to measure the speed of sound back and forth. Schematic like this is good to send pulses: enter image description here

But then I need to switch this transmitter and receiver actuator. How to do this? Use mux? Or there is some generic driver schematic, which combines high-voltage sender circuit plus input amp?

  • \$\begingroup\$ Have a look at the SRF04 module schematic. These modules are so cheap that it's not worth doing your own design. The circuit you've shown uses a chip designed for RS232 serial line level conversion so it is either very clever or totally bonkers. I don't know which. \$\endgroup\$
    – Transistor
    Apr 19, 2020 at 21:04
  • \$\begingroup\$ @transistor Note that the MAX232 chip is used in the SRF04 to generate a higher voltage drive for the transmitting transducer. The schematic shown in the question is not as complete as that in the SRF04. \$\endgroup\$
    – Barry
    Apr 19, 2020 at 21:44
  • \$\begingroup\$ I didn't notice that. I had been looking at the modules earlier in the evening before the question was posted. OK, I've decided that it's very clever then. \$\endgroup\$
    – Transistor
    Apr 19, 2020 at 21:49


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