I'm trying to build a simple buzzer testing circuit using an STM32 microcontroller and an SI2302 N-channel MOSFET. The buzzer is supposed to be controlled via a GPIO pin, but it's not working as expected—there's no sound output.

Here’s a summary of my setup:

• Power Supply: 5V
• MOSFET: SI2302DS
• Buzzer: Connected between MOSFET drain and GND
• Gate Drive: STM32 GPIO pin through a 100Ω resistor
• Flyback Diode: DSK24 across the buzzer (anode to 5V, cathode to drain)

Symptoms:

• No sound from the buzzer.
• GPIO pin is toggling between 0V and 3.3V as expected.
• Verified connections and component values.

Questions:

1. Is this circuit Wrong?
2. Is the SI2302 suitable for switching a buzzer at 3.3V logic?
3. Could the buzzer require more current than the MOSFET can handle?
4. Is there anything wrong with the way the diode or pull-up is connected?

 

hi Noob,
The diode is shorting the buzzer, its forward biassed.
E

Is the SI2302 suitable for switching a buzzer at 3.3V logic?

Yes.

 

hi Noob,
Welcome to AAC
Is this a Homework or College assignment?

Moderation.

 

i am new to electronics trying to fit in.

 

Thank you sir for your response,

is there anything else i need to take care in this schematics?

hi Noob,
The diode is shorting the buzzer, its forward biassed.
E

Yes.
View attachment 349588

 

Just a couple minor corrections:

1. Your buzzer is connected between the drain and VDD, not GND.

2. Your "pull" resistor is actually a pull-down not pull-up.

 

Turn D1 around or remove it entirely from the citcuit.

 

You have to post the corrected circuit, so our members can check it.

What is the minimum voltage that is required to drive the buzzer?

Did you test the Buzzer before you connected to the circuit?

 

Buzzers typically draw around 30-80mA.

The diode can be an ordinary 1N4148 instead of schottky.

The mosfet can, instead, be a 2N2222 with a 1k base resistor.

 

Simulation showing a setup for an N-Channel Mosfet. Having on hand a momentary switch and a small red led can be helpful and intuitive.
1.8V Vcc was not sufficient because R1 and R2 formed a divider. Increasing Vcc to 2V worked. The STM32 GPIO is also sufficient if not overloaded.
In this circuit I was concerned with a minimal or adequate current for the led and determined the value for R3 to be 1.4K
The diode has a band indicating cathode. See inductive kickback with protection. The diodes direction is shown in figure C AAC book link.
figure d shows what that transient looks like on a scope when a momentary switch is released but I don't advise connecting a scope.
Inductor Commutating Circuits | Diodes and Rectifiers | Electronics Textbook


How can this circuit be modified to give relevant test results to help determine best parameters for your buzzer?

.
The link below discusses how others have configured buzzers and some of the confusion in uC applications.
The link below shows various buzzer specs and overall scheme

How to use a buzzer - the correct way - Tech Explorations

 

Hi everyone,

Thank you everyone for sharing your responses and with all your help i was able to get more knowledge and done the circuit successfully and here attached is the simulation that i have done in LTpsice and it is somewhat matching my circuit.
Anyway there will be more doubts coming because i just started.