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Original question:

PGA450-Q1: Object detection at two different distance

PGA450Q1EVM: different transducer problems

Lennert Es
Prodigy 30 points
Part Number: PGA450Q1EVM
Other Parts Discussed in Thread: PGA450-Q1, , PGA460, PGA460-Q1

Hello,

I have a PGA450-Q1 EVM, and connecting the included 58kHz transducer works fine.
I would like to switch to the 48kHz transducers from Bosch:

I have removed the piezo element (snap connector) from the rest of the module and attached it to the EVM.

I have changed the frequency settings to 48kHz and updated the band pass filter parameters, but the EVAL MONITOR just shows a single peak (around sample 90) every time, even when the piezo element is not connected.

There is no further information about these transducer other than that their frequency is 48kHz. Is there any reason for this combination not to work ?

Kind regards,

Lennert

  • 0
    TI__Genius 11015 points
    Hello Lennert,

    We will get back with you soon.
  • 0 in reply to Bharat Aravamudhan
    Prodigy 30 points
    Thank you very much! Some extra information:
    I assume the piezo element in the Bosch sensors is similar to this one:
    www.farnell.com/.../1759994.pdf

    It has the same frequency, dimensions, directivity gain and operating temperatures. This transducer is 160V p-p and 48kHz which should work with the PGA450Q1EVM is i understand correctly.

    Kind regards,

    Lennert
  • 0
    TI__Mastermind 27920 points
    Hi Lennert,

    The small peak at sample 90 is a false positive created by GUI-SPI communication in the background, and can be ignored on the GUI.

    As for the Bosch transducer, the driver and receiver specifications/rating are not publicly available, so I do not know if it is compatible with the PGA450. You can probe the transducer's positive terminal to check if a sinusoidal 48kHz waveform at 100~200Vpp is generated by the PGA450 + transformer + transducer.

    I suspect the matching components (transformer secondary inductance and/or parallel tuning capacitor values) need to be modified to match the resonance of the transducer. Otherwise, the driver may be distorted, resulting in a low sound pressure level from the transducer.

    Have you considered using the PGA460-Q1 instead of the PGA450-Q1? Also, you can find a list of off-the-shelf closed-top transducers on the PGA460 support page as: "PGA460 Transducer & Transformer Listing" ( www.ti.com/.../slac787 ). The PGA460 is the latest air-coupled ultrasonic sensing device from TI, wiht improved performance, lower cost, and smaller size.
  • 0 in reply to Akeem Whitehead
    Prodigy 30 points

    Dear Akeem,

    I confirmed that there is indeed a 48kHz waveform of 150V pp.

    I have switched to the following transducer from the provided list: Multicomp MCUSD17.5A48S11RS-30C. This transducer has the same characteristics (voltage,frequency,dimensions,directivity) as the Bosch ones and works fine with standard transformer.

    Kind regards,

    Lennert