On 9/8/05, Michael Rigby-Jones wrote: > >After a while, you notice the similarity in the schematic > >between a charge pump voltage doubler and your piezo element > >and port pins, and you realize that every time you flip the > >piezo, you are flirting with SCR Latchup or glitching your micro. > > > > Interesting, I can see the potential issue. A pair of schottky diodes on each pin would solve this problem. Driving a Piezo in this manner from any CMOS based IC, such as HC inverters risks the same problem, though latching up your piezo driver is preferable to the micro I guess ;) > What if you gave the piezo enough 'dead time' to drain its charge? E.g. instead of: 10 01 10 01 Use this sequence: 10 00 01 00 10 00 01 where '00' is long enough to let the charge drain out. (A resistor across the buzzer might help speed it up). Regards, Mark markrages@gmail -- You think that it is a secret, but it never has been one. - fortune cookie -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist