I'm trying to design a schematic to drive ultrasonic transducers for pinging objects underwater (sonar) The transducers I am looking at are 40khz used for ultrasonic cleaning, and rated to 50 watts
I want to make the schematic as simple as possible while still functional. This means I don't want a lot of hardware drivers or filters if possible. Instead, the stm32 uC have fast adc, and can easily output pwm in the desired frequencies.
DriveA and DriveB signals are produced by the microprocessor at the right frequency as inverted waveforms with dead time.
The T1 transformer will have 15 turns for each primary, and a secondary with 100-200 turns to produce a drive voltage of 200 Vp-p to the transducer.
The resistor R2, I am not really sure the correct value, I will try with 280 ohms to start out.
The Diodes D1 and D2 are fast recovery.
The idea of the diodes D1-D4 and R3 (also not sure of optimal value) to allow measuring the millivolt returns from the transducer, but not allowing the large drive voltages into the receiver.
C2 is to balance the transformer capacitance to ground.
TR1 transformer could be an audio transformer with a few hundred turns windings, probably 1:2 ratio
The opamp is to amplify the return signal for the adc range, I can tune the gain with a screwdriver. The actual filtering (besides the simple high-pass filter) is to be done in software.
Almost all other examples I see have a lot of filters in hardware which significantly complicates the design, can this really be avoided? Filtering in software allows for changing the transducer frequency, operating at secondary resonance frequency (170khz) as well as for detecting frequency change (doplar shift) of moving targets. I can also produce waveform of variable duty cycle to reduce power consumption depending on target range.
Will this work? How could I improve it? Recommended components? Am I missing anything critical?
Would it be better to have two transducers, one for transmit, and another as receiver?
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