Newsgroups: comp.robotics
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From: robertj@malibu.sfu.ca (Robert John Johnson)
Subject: Switching Ultrasound Signals
Message-ID: <robertj.755740452@sfu.ca>
Sender: news@sfu.ca
Organization: Simon Fraser University, Burnaby, B.C., Canada
Date: Sun, 12 Dec 1993 23:54:12 GMT
Lines: 32

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.

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.
I know that TRIACS can be hooked up with opto-isolators to be controlled by
binay levels which is required here.

The signals are about 150VAC plus 150VDC I believe.  
There is a maximum of about 100mA.
The "on" impedence is not crucial, however "off" impedence is crucial to
eliminate cross talk.



Would you please e-mail responses.

Thank you

Robert Johnson
(robertj@sfu.ca)

