![]() ![]() To add a further complication, ideally i'd like a solution with the lowest "stack" height possible! (the buzzer solution, vent and hole is "tall") My current best solution, but with completely unproven provenance is to use one (or more) flat piezo sounders like this: Which i plan to mount in a shallow recess machined into the top of the alluminium case of the HMI, and to cover that sounder with the decal that acts as the waterproofing agent for the LEDs/ Buttons. What i'd like to do is to simplify (and potentially reduce cost too) that solution, ie to provide a relatively loud (>85dB) sound indicator to the user, but the solution must be waterproof and pass some stringent EMC requirements too (hence the previous buzzers being inside the box). An existing product uses pcb mounted buzzers, pointing out sideways, through gore vents, to provide a small range of "beeps and chimes" to indicate operational events. # include "pitches.I have a project where we would like a haptic feedback beyond that provided by the actual buttons and indicator leds on the HMI. The pitches library is not found in the Arduino IDE but you can download the ZIP file from Github and include the library in the Arduino IDE by clicking in the menu line: Sketch -> Include Library -> Add. If you take a look into the source code of the library you see that the library is nothing else than a lookup table for different notes to their frequency. You could now use the tone function and define the connected output pin, the frequency and the duration of the output generation, but if you do not know the frequency of different notes, we can also use the pitches library from Mike Putnam. Instead we use the Arduino tone function to generate a square wave of the specified frequency (and 50% duty cycle). Therefore we can not use the analog write function, because this function has a fixed frequency of 500Hz. ![]() To create a melody the passive buzzer needs an AC signal where we can define the frequency. Let me know in the comment section if you know the melody that we create in this example. The passive buzzer has the advantage that we can not only create a tone, but also a melody with different frequencies. The digital I/O pin of the Arduino, EPS8266 or ESP32 microcontroller is therefore connected to the gate of the MOSFET with a resistor of 220Ω in series, because the Arduino operation voltage of 5V or even the 3.3V operation voltage of the ESP8266 or ESP32 would damage the transistor. Otherwise we were not able to switch off a load that has a higher voltage than the control voltage. Low-side switch: The transistor is on the low (ground) side of the circuit and the buzzer is connected on the high (5V or 3.3V) side.NPN transistor: Because we want to turn the active or passive buzzer on by setting the digital pin of the microcontroller HIGH.In my case I use the IRLZ44 NPN MOSFET as low-side transistor to control the buzzer. ![]() ![]() The solution is to use a transistor and divide between the control signal and the power consumption. But if we want to use magnetic buzzers with a current consumption higher than 20mA we have to find a different power supply than the digital I/O pin of the microcontroller. Piezo buzzer have a current consumption lower than 20mA and could therefore be powered by Arduino microcontroller as well as the ESP32. ![]()
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