On 2009-01-26, Lie Ryan <lie.1...@gmail.com> wrote:
> How about (a crazy idea) using the audio jack out? (DISCLAIMER: Little
> Hardware Experience). High pitched sound (or anything in sound-ology that
> means high voltage) means the device is on and low pitched sound off.
1) Pitch has nothing to do with voltage. A high-pitch sound
and a low pitch sound can have the exact same voltage.
2) The OP's device requires quite a bit of power. There is
almost no power available from the line-out jack, and the
voltage is limited to about 1V. If his sound card has a
power-amp (none do these days), he might be able to get a
usable amount of power.
> The device will need an additional transistor to separate low
> voltage from the high voltage.
He'll need more than a transistor. He needs a power supply,
some sort of rectifier/detector, and a comparitor. It would be
more interesting to use notch filters to detect different
frequencies so that you could have multiple output "bits".
> I don't know how much power can be pulled from jack out,
Almost none, and what's there is very low voltage.
> but for a home brewn device it is still feasible to draw power
> from USB and signal from jack out.
It would probably be easier to buy a USB-parallel port chip.
Then he's got power from the USB bus and something like 14
parallel I/O pins he can control. Alternatively A USB-serial
chip will provide 2 outputs and 4 inputs.
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