Hi John, Andrew and all interested people,

Andew asked:
> > >Does anybody know how to produce a reasonably loud "click" from a
> > >3V battery powered circuit?  I tried sending a square pulse to a
> > >teensy weensy miniature speaker, but it's very quiet.

Someone answered:
> > Instead of a click, try getting a very short beep - just a few cycles worth.
> > If the 3V is not enough you could use an H bridge to drive it. Two LM 386s
> > or something similar should do it.

John replied:
> Actually, I'd suggest sending it a short burst of "random" pulses.
good idea!
>
> Also, for output you could tie one leg of the speaker to a port pin, and
> the other to a port pin via a cap.  If both port pins switch simultaneously
> in opposite directions you could get +/- 6 volts on the speaker which should
> give it a louder drive than merely using a single port pin.
But why do I have to tie one leg of the speaker to a PIC pin _via a cap_?
It _is_ the advantage of a bridge speaker driver not to need any cap!

For example, have a look at the data sheet of a TDA7052 audio amplifier
(from Philips). The data sheet proudly claims that no external components
are needed (well, except for 1 resistor and 1 big cap for Vdd).
I think this IC could be used as a single-chip solution for the speaker-driver
problem, although it might not be the cheapest way.


Merry Christmas! - Frohe Weihnachten!

Siegfried