Microbuzzer.com · Posted on 06-08-2010 by microbuzzer

Buzzer sound principle is current through electromagnetic coil, electromagnetic coil creates a magnetic field to drive the diaphragm sound, and therefore need a certain current to drive it, MCU IO pin output current is small, microcontroller output TTL level Basically, a buzzer driver can not, therefore need to increase a current amplification circuit. S51 Enhanced MCU Board C8550 through a transistor to amplify drive buzzer.

Buzzer’s positive received VCC (+5 V) power supply above the negative received buzzer transistor emitter E, base-class B transistor through the current limiting resistor R1 by the MCU after the P3.7 pin control, when the P3 .7 output high, the transistor T1 end, no current flows through the coil, the sound is not audible; when the P3.7 output low, the transistor conduction, so the current formation of the buzzer circuit sound. Therefore, people can be programmed P3.7 foot level to make the buzzer sound on and off. MCU P3.7 pin programs the output waveform to change the frequency, you can adjust the tone control the buzzer to produce a variety of different sounds, tone of voice. Also, change the P3.7 output level of high and low duty cycle, you can control the size of the buzzer sound, which can be programmed to verify the experiment.

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