On Mon, 26 Jan 2009 11:08:48 -0600, Unknown wrote: > 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".
>From the little I know on electronics, a simple, single transistor would (almost) immediately switch from on-to-off-to-on depending on the voltage of the control pin (I think it was the middle pin). I was suggesting this simplistic hack because as far as I comprehend the OP's need, he only need on-off switch instead of a complex 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. That's why the power is taken from USB port. >> 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. The idea was made on the basis that a USB microcontroller is not used. Getting power from USB should be much easier than getting data while the jack out can provide simple on-off signal. -- http://mail.python.org/mailman/listinfo/python-list