Subject:
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Re: sonar (fwd)
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 18 Nov 1996 06:09:56 GMT
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Original-From:
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Richard Vannoy <richardv@abac.AVOIDSPAMcom>
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Viewed:
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997 times
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Just to add a basic newbie note on receiver blanking that will have to be designed in
if you build it yourself.
A transmit pulse is a very powerful (relatively speaking) pulse. For example, the
Polaroid transducer, about the size of a silver dollar, puts out 400 volts at two
amps for several milliseconds. If the receiver is left on, the shock of the transmit
pulse will rattle around the mechanics and the receiver causing all kinds of false
signals. On transmit, the receiver must be turned off for a short period. Just
enough time to let the transmitted pulse "get away" from the transmitter, and for any
mechanical "ringing" in the mechanics to fall off. The blanking signal turns the
reciever back on a few milliseconds later, so the first echo (hopefully) will be of
an external target, and not residue of the transmit pulse. Polaroid has receiver
blanking built in, and steps up the gain of the receiver every few feet to compensate
for the rapid attenuation of the returned signal. As an ex-sonar technician, I STILL
don't want to design all that from scratch, therefore $50 per unit for Polaroid seems
like a great bargain to me unless the hobbyist really gets off on building from
scratch.
> Basic idea behind Sonar is this: Send a pulse with the transducer. The
> sound pulse travels across the room, hits an object, and reflects back (and
> everywhere else). The time that it between when you sent the pulse and
> when you recieved a return pulse is twice the time that it takes sound to
> travel to the nearest object in the line of the pulse.--
Richard T. Vannoy II richardv@abac.com
PO Box 103 Computer Programmer
La Mesa, CA 91944-0103 College Electronics Instructor
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Message has 1 Reply:
 | | Re: sonar (fwd)
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| (...) This is true of the POLAROID Ultrasonic Sensor module, but not necessarily true of all Ultrasonic Sensor modules. It depends on the type of Ultrasonic Transducer the circuit uses. The one I built uses a Piezo-Electric transducer available (...) (28 years ago, 23-Nov-96, to lugnet.robotics.handyboard)
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