Newsgroups: comp.robotics
Path: brunix!sgiblab!swrinde!elroy.jpl.nasa.gov!decwrl!news.kpc.com!amd!netcomsv!netcom.com!nagle
From: nagle@netcom.com (John Nagle)
Subject: Re: Switching Ultrasound Signals
Message-ID: <nagleCI0HEw.D3s@netcom.com>
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
References: <robertj.755740452@sfu.ca>
Date: Tue, 14 Dec 1993 06:16:07 GMT
Lines: 32

robertj@malibu.sfu.ca (Robert John Johnson) writes:
>Greetings:
>I am working on a robot project with ultrasound.
>We have 12 transducers, and 3 driver boards, with each driver board driving
>4 transducers, with relays switching between the 4.
>There are two problems with this arangment:

>1) The noise!!  This robot is suposed to act like a dog, but it sounds more
>like some sort of bug or something with these 9 relays switching.

>2) Reliability.  We wonder how long the switch contacts will last running at 
>about 32Hz.

      I used DIP-mounted reed relays for that, and they are rated for a
few million operations.  What are you using?

>What we are looking for is a way to switch the signal with semiconductors.
>I was wondering about TRIACS; they can handle high voltage and alternating 
>current, correct.

      If you're using the same transducer for input and output, power triacs
aren't going to work.  They won't pass the very weak signal received.

      Why not just get, or build, more driver boards?  Probably easier
than trying to build electronics to switch the outputs.  The circuit for
the board is available as TI data sheet D2842 (January 1985) for the
SN28828 ranging module.  If you send me a stamped, self-addressed 
A-size envelope, I'll send you a copy.

					John Nagle
					999 Woodland
					Menlo Park, CA  94025
