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ESP32 Bluetooth - 40 kHz pulse for dog barking transmitter

walkquera 459 11
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Treść zostaĹ‚a przetĹ‚umaczona polish » english Zobacz oryginalnÄ… wersjÄ™ tematu
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  • #1 21887070
    walkquera
    Level 2  
    Hi,

    i am working on a simple project on ESP32 and would like to build a circuit:

    - ESP32 (Bluetooth)
    - receiving a signal from a phone/tablet
    - generation of an ultrasonic signal of approx. 40 kHz
    - control of ultrasonic transducer

    Premise:
    When a Bluetooth signal is received - a short ultrasonic pulse is generated.

    This is a hobby/test project.

    I would welcome suggestions:
    - how best to implement 40 kHz generation
    - whether a MOSFET would be a good solution
    - what components do you recommend

    If anyone has experience with such projects and would like to help with implementation - also welcome to contact me.

    Thanks!
    Remek
    AI: What exact ultrasonic transducer do you want to control (model or at least parameters: operating voltage, power, resonant frequency)?
    At this stage I do not yet have a specific model.
    I am assuming an ultrasonic transducer with a frequency of about 40 kHz (typical commercially available components, e.g. as in the HC-SR04 sensors).
    Power supply in the range 3.3V-5V (possibly with a driver).
    AI: What do you want this "short pulse" to look like - how many cycles / what duration and from what voltage do you want to supply the transmitter?
    I understand a short pulse to be a signal of about 40 kHz lasting between about 0.2 and 1 second.
    At this stage I am assuming ESP32 level control (PWM or tone), with adjustable pulse duration.
    I plan to supply the transmitter from the 3.3V-5V range (or via a transistor/MOSFET if required).
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  • #2 21887361
    inot
    Level 38  
    Perhaps a little help in solving how to control the audio transducer: Link
  • #3 21887435
    ArturAVS
    Moderator  
    @inot This is not the way to control an ultrasonic transducer, it's using an off-the-shelf module. You need to use a PWM and generate 40 kHz with it and feed this signal to the GPIO. Only with this signal you control an external mosfet transistor which acts as an amplifier.
  • #4 21887441
    inot
    Level 38  
    The author of the topic mentioned this module and perhaps he intends to use it. Otherwise, it is difficult to advise anything without knowing what converter he intends to use.
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  • #5 21887444
    ArturAVS
    Moderator  
    I see no mention of the HC-SR04 there. That is not what this module is for.
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  • #6 21887707
    walkquera
    Level 2  
    Thanks for the tips and help đź‘Ť
    Now I understand that the HC-SR04 is not the solution and you have to go in PWM 40 kHz + MOSFET + TX converter.
  • #7 21887761
    inot
    Level 38  
    walkquera wrote:
    you need to go with a 40 kHz PWM + MOSFET + TX converter

    It depends on which sensor you intend to use. For example, there are sensors controlled via the RS-485 bus.
  • #8 21887781
    ArturAVS
    Moderator  
    The HC-SR04 works similarly to a sonar/radar.
    inot wrote:
    There are, for example, sensors controlled via the RS-485 bus.

    You are suggesting more and more complicated things to beginners. Here you literally only need a few elements and a few lines of program.
  • #9 21887905
    inot
    Level 38  
    walkquera wrote:
    Summary:P of receiving a Bluetooth signal

    I misunderstood the author's intentions. This is only about the generation of the 40 kHz signal, not the distance measurement. I assumed that the result of the distance measurement should result in a Bluetooth signal.
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  • #10 21888119
    tesla97
    Level 20  
    Use the module from the ultrasonic cleaner, you immediately have a power supply and an emitter. Note the high voltage, even a few kilovolts. For this, power is 40, 60, 80W.
    You can buy the finished product on auction portals.
  • #11 21888745
    ArturAVS
    Moderator  
    tesla97 wrote:
    Use the module from the ultrasonic cleaner,

    Maybe still from an industrial one? What are you writing about, man? Do you want him to hurt himself?
  • #12 21889006
    inot
    Level 38  
    Back to the query:
    walkquera wrote:
    I assume control from ESP32 level (PWM or tone), with adjustable pulse duration


    The tone function will be a good option. Using a variable, the duration of the signal can be specified immediately.
    Code: Arduino
    Log in, to see the code
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FAQ

TL;DR: For ESP32 hobby builds, generate 40 kHz from PWM or tone(), then switch a separate ultrasonic transmitter through a MOSFET stage. As one expert put it, "you need PWM and generate 40 kHz". This FAQ helps makers trigger a short 0.2-1 s ultrasonic burst from a phone or tablet over Bluetooth. [#21887435]

Why it matters: It separates the correct low-part-count transmitter design from wrong module choices and unsafe high-voltage ideas.

Option What it does Fits this project? Notes
ESP32 PWM + MOSFET + TX transducer Generates and amplifies a custom 40 kHz burst Yes Recommended simple path in the thread
ESP32 tone(pin, frequency, duration) Generates timed frequency output Yes Good when adjustable duration matters
HC-SR04 module Complete distance-sensing module No Not meant as a custom TX driver
Ultrasonic cleaner module High-power cleaner driver No Thread warns about kilovolt-level risk

Key insight: Use the ESP32 only to generate the 40 kHz control signal. Let an external MOSFET stage drive the ultrasonic TX element, not the GPIO alone. [#21887435]

Quick Facts

  • Target signal in the thread is approx. 40 kHz, with a short pulse of about 0.2 to 1 second. [#21887070]
  • The proposed supply range is 3.3 V to 5 V, either directly at logic level or through a transistor or MOSFET driver stage. [#21887070]
  • The final working direction accepted in the thread is 40 kHz PWM + MOSFET + TX transducer rather than an HC-SR04 module. [#21887707]
  • One reply suggests tone(pin, frequency, duration); because it sets frequency and duration in one call. [#21889006]
  • Ultrasonic cleaner modules were flagged as risky because they can involve high voltage, even a few kilovolts, and 40, 60, or 80 W power. [#21888119]

How do I generate a 40 kHz ultrasonic pulse on an ESP32 when a Bluetooth signal is received from a phone or tablet?

Use the ESP32 to start a 40 kHz output as soon as your Bluetooth event arrives. A simple flow is: 1. detect the phone or tablet signal, 2. start PWM or tone() at 40 kHz, 3. keep it on for 0.2 to 1 second, then stop. That matches the stated project goal of a short ultrasonic burst triggered by Bluetooth, using adjustable duration on ESP32. [#21887070]

What's the best way to drive a 40 kHz ultrasonic transducer from an ESP32 GPIO: direct output, PWM, or a MOSFET stage?

The best thread-backed approach is PWM from the ESP32 plus an external MOSFET stage. One expert answer states you should generate 40 kHz with PWM on a GPIO, then use that signal to control an external MOSFET that acts as an amplifier. That gives you the correct control structure for a 40 kHz TX transducer, instead of treating the GPIO as the final power driver. [#21887435]

Why isn't the HC-SR04 module the right solution for transmitting a custom 40 kHz pulse from an ESP32?

The HC-SR04 is not the right choice because it is a complete sonar-style distance module, not a simple custom transmitter stage. The thread explicitly says that link-based HC-SR04 advice was not the way to control an ultrasonic transducer for this project. Here, the need is custom 40 kHz generation from ESP32 plus external drive, not off-the-shelf ranging hardware. [#21887435]

What components are typically needed to build an ESP32-based 40 kHz ultrasonic transmitter powered from 3.3V to 5V?

A minimal build needs an ESP32, a 40 kHz TX ultrasonic transducer, and a MOSFET driver stage. The original project assumes 3.3 V to 5 V supply, adjustable pulse duration, and optional transistor or MOSFET drive if the transmitter needs more than GPIO-level control. The thread later confirms the practical direction as 40 kHz PWM plus MOSFET plus TX transducer. [#21887707]

How should I choose a MOSFET for amplifying a 40 kHz PWM signal from an ESP32 to an ultrasonic transmitter?

Choose a MOSFET only after you know the exact transmitter and supply range. The thread repeatedly points out that advice gets fuzzy without a specific transducer model, operating voltage, or power. In this project, the stated assumptions are about 40 kHz and 3.3 V to 5 V, so the MOSFET must match that chosen TX element rather than the ESP32 alone. [#21887441]

What is an ultrasonic transducer, and how is it different from a complete module like the HC-SR04?

"Ultrasonic transducer" is an acoustic component that converts an electrical 40 kHz signal into ultrasonic vibration, unlike a complete module that already bundles control and measurement electronics. In this thread, the needed part is a standalone TX element, while the HC-SR04 is discussed as a sonar-style module used for distance measurement. [#21887781]

What is a MOSFET, and what role does it play in an ESP32 ultrasonic transmitter circuit?

"MOSFET" is a transistor that switches or amplifies an electrical signal, letting a low-power GPIO control a higher-power load. In this circuit, the ESP32 produces the 40 kHz control waveform, and the MOSFET stage drives the ultrasonic transmitter more strongly than the GPIO alone. That role is described directly as an amplifier stage in the thread. [#21887435]

ESP32 tone() vs PWM for 40 kHz signal generation — which approach is better for adjustable pulse duration?

For adjustable duration, tone() is the simpler option named in the thread. One reply says tone(pin, frequency, duration); is a good fit because the duration can be specified immediately with a variable. PWM still matches the recommended control concept for driving an external MOSFET stage, so tone() is easier for timing while PWM is the clearer hardware-drive explanation. [#21889006]

How many cycles or what pulse duration should I use for a short 40 kHz ultrasonic burst if I want something between 0.2 and 1 second?

Use a burst duration between 0.2 second and 1 second, because that is the exact range defined for this project. At 40 kHz, that means the burst lasts for a controlled time window rather than a single click. The thread does not fix a cycle count, but it clearly defines the practical target as a 40 kHz signal with adjustable duration in that 0.2-1 s range. [#21887070]

What problems can happen if I try to power a 40 kHz ultrasonic transmitter directly from a 3.3V ESP32 pin?

You can end up with weak drive or an unsuitable output stage. The thread’s correction is clear: generate 40 kHz on the GPIO, then use that signal to switch an external MOSFET amplifier. That warning exists because the accepted solution moves power drive away from the ESP32 pin and toward a dedicated stage, especially when the transmitter may run from 3.3 V to 5 V. [#21887435]

How do I wire an ESP32, a MOSFET, and a 40 kHz TX ultrasonic transducer into a simple working circuit?

Wire the ESP32 GPIO to the MOSFET control input, and use the MOSFET stage to drive the 40 kHz TX transducer from the chosen supply. The thread’s simple architecture is ESP32 PWM at 40 kHz, external MOSFET as amplifier, and a separate ultrasonic transmitter element. That is the exact beginner-friendly path defended in the discussion as only a few parts plus a few program lines. [#21887781]

What is RS-485, and in what kind of ultrasonic devices would it be used instead of a simple PWM-driven transducer?

"RS-485" is a serial communication bus that links digital devices over a defined interface, unlike a bare transducer that only needs a drive waveform. In the thread, RS-485 is mentioned as something used by some ultrasonic sensors, not as the right default for this simple ESP32 transmitter project. It refers to more integrated sensor hardware rather than a raw 40 kHz TX element. [#21887761]

Which 40 kHz transmitters similar to those used in sonar or HC-SR04-style devices are suitable for a hobby ESP32 project?

A suitable choice is a typical 40 kHz ultrasonic transducer like the kind used in HC-SR04-style devices, but as a standalone TX element. The original post explicitly mentions assuming a commercially available 40 kHz transducer of that general type, powered in the 3.3 V to 5 V range, possibly with a driver. That makes it aligned with a small hobby ESP32 build. [#21887070]

What safety risks come with using ultrasonic cleaner modules or high-voltage ultrasonic drivers for a small ESP32 test build?

The main risk is dangerous voltage and excessive power for a small bench project. One thread reply says ultrasonic cleaner modules can involve even a few kilovolts and 40, 60, or 80 W, and another reply reacts by warning that this could hurt the builder. For a simple ESP32 test build, that makes cleaner hardware a poor and potentially unsafe choice. [#21888745]

How can I troubleshoot weak output or no sound from an ESP32-driven 40 kHz ultrasonic transducer?

First, confirm you are using a standalone TX transducer, not an HC-SR04 module. Next, verify the ESP32 is actually generating 40 kHz and that the burst lasts the intended 0.2 to 1 second. Finally, check that the MOSFET stage sits between the GPIO and transmitter, because the thread’s accepted fix for this project is 40 kHz PWM plus MOSFET plus TX transducer. [#21887707]
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