> >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.
> >
>
> 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.

Actually, I'd suggest sending it a short burst of "random" pulses.  Metronomes
that beep with a definite pitch can be a bother musically if their output is
off-key.  If you use random pulses, the resulting sound would be white or pink
noise, and thus less likely to be bothersome.

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.