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DPRG: Re: Audio

Subject: DPRG: Re: Audio
From: Jim Brown jimbrown at airmail.net
Date: Fri Jan 2 16:52:27 CST 1998

Here are some ideas about how to home in on sound.
It appears that you are on the right track.

1. The microphones should be of cardioid pattern (narrow beam) and
should be aimed up (on a short robot) and forwards.
2. Cause the "head" to scan back and forth "pseudo-randomly".
2a.  Or don't scan just wait for a sound.
3. When a mic picks up a sound immediately cause the head to turn in
that direction.
4. When the other mic picks up a sound then cause the head to reverse to
turn in that direction.
5. Eventually the head will search less and less until the target is
homed.
6. The mic signals are fed into schmidt triggers or comparators with
rectification and low passed.  Set the comparators for a particular
threshold.
6a. A cool way to establish a quick form of "pseudo-fuzzy-logic"
performance is to feed the signals into the LM3914 Bar-Dot display
driver chip in dot mode to give an amplitude output.  Use each output to
provide a different speed form the head motor. (I can provide more
simple details on this method.)  A PIC chip would make this easier.
7. After a certain time of interrupted scanning (sound detection) or a
certain number or frequency of mic aquisitions or a certain minimum time
interval of scan reversals, you then cause the robot to turn to the
aquired direction.  You might have the neck tied to a pot or other
encoder to indicate head to body position, then work the robot toward
the zero position by the shortest route.

I have a robot that follows in this manner.  It just uses the mic
signals to momentarily stop the motor on the same side as the mic until
both mics balance.

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> >       I am using a BASIC compiler to program the PIC 16F84-4P as the
> basis
> >for my robotics stuff. I am working on a project in which I want to
> have
> >the robot head turn in the direction of a sound. (Or two eyes with a
> >connecting rod... just one axis)
> >
> >       My thinking is to have two microphones, one per side of the
> head. If no
> >noise is detected, the head will follow a pre-programmed
> "psudo-random"
> >look around mode. If on the other hand one microphone detects more
> noise
> >than the other, the head will tend to turn in that direction until
> the
> >noise is equal from both "ears".
> >
> >       It would be nice if... the robot could tell the difference
> between a
> >soft and a loud noise. I.E. Someone says, "Hello." the robot sorta
> looks
> >in their direction... but if someone yells, the robot looks that way
> >with max speed.
> >
> >       I can take the microphones and run them to an OP-AMP, no
> problem. I can
> >then run the signal to a schmidt triger or other device to turn it
> into
> >an ON/OFF, or use A/D sensors to read the two signals.
> >
> >       Any suggestions on how to go about this project???
> >
> >                               thanks,
> >                               G. Rutherford







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