AVR-Chat

On Thursday 26 May 2005 10:16, Mike Murphree wrote:
> On May 25, 2005, at 8:58 PM, Ralph Hilton wrote:
> > On Thu, 26 May 2005 11:49:45 +1000 you wrote:
> >> Ralph Hilton wrote:
> >>>>> Connect it between 2 output pins and switch them alternately.
> >>>>> That effectively doubles the voltage.

> >>>> How does that work?

> >>> If the 2 pins are alternately pulled up then the peak to peak
> >>> voltage is 10.

> >> Not unless you "store" the voltage somehow. ie. you may need
> >> some diodes and capacitors. At any one time the voltage
> >> measured across the two pins is always no more than Vcc.

> >> Do you do advertisements for amplifiers?

> > Using pins 1 & 2:

> > Pin 1 = 0, pin2 = 5v
> > then
> > Pin 1 = 5v, pin2 = 0

> > Relative to pin1, pin2 goes from +5 volt to - 5 volt which is 10
> > volts peak to peak.

Not really. It's just how it appears (memntarily) at the buzzer.

> This technique was used in car stereo amplifiers before internal
> power inverters became commonplace.  If you connect an oscilloscope
> (with differential inputs) across the buzzer, it will appear to a 10
> volt peak-to-peak waveform even though only 5 volts is applied in
> each half-cycle.

To answer Peter's question; the "storage" device is the buzzer.
It's mostly a capacitor. The gates on the uC act as diodes (when
they go "high").

-- 
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