Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!sco!deanr
From: deanr@sco.COM (Dean Reece)
Newsgroups: sci.electronics
Subject: Re: Motor Position encoder -> digital count value
Keywords: motor encoder interface position
Message-ID: <5171@scolex.sco.COM>
Date: 13 Mar 90 20:43:50 GMT
References: <1745@xn.LL.MIT.EDU>
Sender: news@sco.COM
Reply-To: deanr@sco.COM (Dean Reece)
Organization: The Santa Cruz Operation, Inc.
Lines: 36


In article <1745@xn.LL.MIT.EDU> tj@XN.LL.MIT.EDU (Thomas E. Jones) writes:
...
>Output A    -----   -----   -----   -----
>            |   |   |   |   |   |   |   |
>         ----   -----   -----   -----   -----
>
>Output B      -----   -----   -----   -----
>              |   |   |   |   |   |   |   |
>           ____   _____   _____   _____   _____
>
>Clockwise, time scale increases going right/left.
>Counter clockwise, time scale increases going left/right.
>
>I need to convert this signal to 2 digital lines that would control a standard
>TTL up/down counter.  Standard TTL counters have an U/D' (up, down) signal and
>a clock (count) signal.  I remember seeing very simple circuits to do this,
>perhaps just a few gates and a few F/F's, but I can't find it.

This is easy. I used a similar encoding technique on a trac-ball once:

Every time B is rising while the shaft is rotating CW, A will be high.
Every time B is rising while the shaft is rotating CCW, A will be low.

So if you used an Edge triggered Counter and let B be the Clock signal
and A be direction, it will just work.  For that matter, it doesn't
matter if the counter you use has a positive or negative edge triggered
clock.  All you need to do is swap the A and B signals to reverse the
direction of count relative to the direction of shaft rotation.

Hope it helps --- have fun

 ______________________________________________________________________
| Dean Reece     Member Technical Staff |"The flames are all long gone |
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