piclist 1995\11\07\010431a >
Thread: Piezo Transducer & sonar
picon face BY : Scott Stephens email (remove spam text)

>On Mon, 6 Nov 1995, Errington A wrote:
>> I used a piezo tranducer between PA0 and GND on a PIC84 with no apparent
>> ill-effects.  I don't think you should have any problems with the transducer
>> between two pins.

If you wan't your Piezo disk to keep going & goint, and not depolarize from
DC potential applied across it, use a coupling cap. Piezo disks depolarize
like LCD's over time & temperature.

>I'm working on a small project that uses the PIC as an ultrasonic
>distance detector.  Instead of using a separate chip, I generated the
>40kHz directly from the chip to the transducer (I also tried one with
>a transistor amplifier).  The receiving end (using a 567 tone decoder) did
>not seem to work very well. Has anyone attempted similar projects?
>I need some hints on getting the receiver to work better.

I've read about some, as the idea occured to me to create an array of piezo
disks, which have been etched and enclosed to work at a higher frequency,
for the purpose of a phased-array sonar. (Sometimes I have trouble believing
their are realy fish where I fish)

567 tone decoders are not very sensitive. And five volts isn't very much to
drive the transducer with. Maybe using 12V on the open-collector RA4 could
increase your transmitted power, and using an active-filter amplifier ahead
of your PIC would increase sensitivity.

While I'm waiting I've found the following:

>To all who requested tiff images of my stereo sonar, I have sent ann image of
>the left receive channel.  The right channel is identical.  The transmitter is
>simply connected to a couple of I/O bits from the PIC.  Also included is a 5
>digit display.  The code, designed for a 16C74,  is still in a state of flux,
>but if desired I would be happy to share it.
>Lee Holeva

Could I get that Tiff? Thanks,

( Never got it :( )

L.Kleeman and R.Kuc, "An optimal sonar array for target
localization and classification", IEEE Int Conf Robotics and Automation, May
8-13 1994 San Diego, pp 3130-3135.

A more complete journal paper on the same system is to appear in the
approximately August 1995 edition of International Journal Robotics Research.

Other papers to appear in Intern Conf R&A Nagoya May 1995 are:

H Akbarally and L Kleeman, "A sonar sensor for accurate 3D target
localisation and classification"

M H Hong and L Kleeman, "A low sample rate 3D sonar sensor
for mobile robots"

   Herbert Peremans, Koenraad Audenaert, Jan M. Van Campenhout, "A High-
   Resolution Sensor Based on Tri-aural Perception", Vol 9 No 1 Febr 1993,
   IEEE Transactions on Robotics and Automation

See also: www.piclist.com/techref/index.htm?key=piezo+transducer
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