Microbuzzer.com · Posted on 18-05-2009 by microbuzzer

Piezoelectric buzzer as the audio signal generator has a wide range of uses, low power consumption as they are, sound clarity and penetration. External buzzer drive circuit or drive circuit requirements of oscillation in the resonant frequency of piezoelectric components. Piezoelectric element at its resonant frequency to provide the maximum output sound pressure. However, a resonance frequency of piezoelectric components have the greatest tolerance of ± 15%. Therefore, tuning to the nominal frequency of the external drive circuit is likely to lose the actual point of the resonator. The design is a piezoelectric element driving circuit of the external, it will automatically find the actual resonant frequency.

The working principle is as follows: When a piezoelectric element in the imposition of an AC voltage at both ends, the beginning of the vibration components. If you remove the excitation voltage, the vibration damping in a way will continue, until all stop. These residual vibration in the piezoelectric element to produce at both ends of the oscillation damping. If the excitation signal near the resonant frequency, the vibration will be stronger, the residual oscillations will continue much longer. Determine the actual resonant frequency is near the resonant frequency nominal try all the frequencies, and compare the various remnants of the duration of oscillation.

In this design, Microchip’s PIC18F452 microcontroller, through its I / O pin RB4 and RB3 drive piezoelectric components. The beginning of RB3 zero, RB4 is set to 1, each half cycle of the two overturned, resulting in a changing of the piezoelectric 0V DC offset voltage (VP). In 10 cycles, RB3 remain low, RB4 as an input for the statistical VP low – high and high – low conversions. B port enable “port change interrupt” functions of the time 10 ms, so that an interrupt service routine to increase counter readings, statistical changes in the number of piezoelectric voltage. Procedures for a list of the functions of a presentation. Procedures on the frequency of all possible repeat these steps and determine the number corresponding to the maximum frequency conversion, which is the resonance frequency. This method can be easily extended to the case of multi-resonance frequency.

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