HC573 / ULN2803 Buffer Board

Now I am assembling a HC573 / ULN2803 buffer board.  Earlier I worried that it was a mistake to let the RPi's GPIO pin to drive the buzzer, because when switching off the buffer, there would be a induction coil fly back current which would damage the GPIO pin switching the current.

However, when I dismantled the buzzer, I found that there is a CS9014, a diode and a 330R resistor.  I think it is an oscillator switching on/off the coil attracting and releasing the spring metal plate, making the buzzing sound.

In other words, it is the CS9014 switching the current, NOT the RPi GPIO pin, which only switching on off the 5V0 power to the buzzer.  So I guess the fly back current would only damage the CS9014, not the RPi's GPIO pin.

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