[PD] Sensors

[Johannes Taelman]

On Fri, 31 Oct 2003, matthew jones wrote:

> I really don't understand why people are so hooked up on using MIDI or
> serial/parallel ports for interfacing sensors with pd.  It strikes me that
> the absolute best way if you are at all worried about sample
> rate/quantisation amount is to use the audio signal inputs of your
> soundcard.  some simple circuitry and then you have maybe a 96kHz 24bit
> input - super fast control and with same latency!

Soundcards filter out all dc ("constant bias") on their inputs. You will
not get good measurements from unmodulated, slowly ( <10Hz) varying
signals. You could modulate the sensor signal in some way, but this
requires more analog electronics.

> am I mistaken? has anyone used this to good effect?

Yes, I've used a soundcard to sample ultrasound (sonar) receivers
directly. This is (in my case) a 40kHz modulated signal. This shifts the
demodulation from hardware to software... So 96kHz is usefull - not only
for audiophiles :)

best,
Johannes