Alt-BEAM Archive
Message #02696
To: beam beam@corp.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Tue, 27 Apr 1999 16:54:01 -0500
Subject: [alt-beam] Re: Bicore head targeting?
Another possibility is to run the output through a diode, and have it
attach to the enable of an oscilator (either actualy activate and
deactivate it, or run the oscilator all the time and simply run the
output and enable through an and gate). The output from that leads to a
counter. a long duty cycle (high time of bicore longer than low time)
should run the counter longer than a low duty cycle. The counter should
be level triggered, so when the output goes low it resets, but there
should be a latch attached to the counter with a transition trigger
(capacitive trigger). the latch loads the data before the counter
resets. When the bicore goes high again, the counter begins counting,
and then it repeats. It's the same operation as a "step up" Analog to
Digital converter. The diference, is we cut the Comparitor and DAC and
take the input straight off the bicore.
Steven Bolt wrote:
>
> On Tue, 27 Apr 1999, Dave Hrynkiw wrote:
>
> > At 01:00 PM 4/27/99 , Dennison wrote:
> > >
> > > My first Idea was to connect both outputs in some fashion to
> > > the +v or gnd side of a sizable cap. The idea goes that, while
> > > one output charges the cap, the other output discarges. When
> > > the pulse durations are equal, then in theory the average net
> > > change in voltage across the cap should be zero.
> >
> > Actually, average would be 1/2 way between Gnd and Vcc. I'd
> > probably start by pumping the signal thru a diode into a RC
> > network (so the signal levels slowly decay), and use a logic gate
> > to compare them. Well, why stop a logic gate? An opamp would be
> > ideal to detect less-than-equal-but-opposite input signals.
>
> Here is another possibility: pulse frequency. Count the left/right
> pulses together without caring which is which. When the head is
> searching, frequency will be low, rising quite steeply when
> `lock-on' is achieved.
> Triggering some other process when a certain frequency is exceeded
> is quite easy, using a counter and a reset signal. When the
> frequency is high enough to pass a certain counter value before
> reset occurs, you have your trigger.
>
> Best,
>
> Steve
>
> ----------------------------------------------------------------------
> # sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
> ----------------------------------------------------------------------
--
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
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