I just hook a piezo up directly to the PIC pins, but if you excite the
     piezo at or near its resonant frequency you might need a resistor to
     prevent excessive flexing of the disc.  You won't need a capacitor if
     you drive the piezo with two output pins.  Drive the two pins in
     opposition (an XOR works well for this), and when the sound is off
     just make sure that both pins are set to the same level.  If you drive
     a peizo with one pin relative to GND or Vcc a series cap might be a
     good idea since otherwise the disc will be forced to flex in one
     direction only.

     A piece of advice - try several different types of piezos with your
     design, the actual sound level and sound quality produced varies
     widely.  If you find you are overdriving the piezo because you need to
     run it near its resonant frequency, trying a different piezo can solve
     the problem easily.


     CIAO - Martin.


______________________________ Reply Separator _________________________________
Subject: Piezo speaker with PIC
Author:  pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU> at
Internet
Date:    5/28/98 9:04 PM


I want to add sounds to a product--beeps and boops and the like.

Can I just hook a piezo speaker to a PIC output pin?
Or should I use a resistor and/or capacitor in series?