Alt-BEAM Archive
Message #09818
To: beam@sgiblab.sgi.com
From: Dave Hrynkiw dave@solarbotics.com
Date: Sat, 05 Feb 2000 17:19:57 -0700
Subject: [alt-beam] Re: Hextile board Question
At 12:40 AM 2/5/00 , Geoff Waters wrote:
>Hi- Everyone's always talking about "Hextiles". I think i've seen these
>things before, they're hexxagon shaped PCB's, but what exactly are they?
>Mark Tilden uses them, right?
Yes, Mark designed a series of 6-sided construction PCB's to assist him in
the construction of his robots. Although similar in size/shape, there were
many variations, each designed for a different task. One would be a
microcore "brain", another would be a bicore "brain", another would be a
74xx245 motor driver, another a H-bridge driver, another a sensor input
conditioner board, etc, etc.
The hex pattern gave him an easy way to nest combinations of boards
together into an array that would do the duties he needed for a particular
design. He's recently gone towards more square shapes, as they give a
better density ratio.
Regards,
Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com
9819 Sat, 5 Feb 2000 17:12:09 -0800 [alt-beam] Re: VSPANS (was: The 240 microcore - was: Bicore question) "'beam@sgiblab.sgi.com'" Wilf Rigter Hello Jean,
Sorry for the long delay but six grueling 14 hr days in row has made a
serious dent into my BEAM up time. But finally a break, at least enough for
a short tantalizing reply.
Isn't it remarkable that the understanding of the operation of such a simple
circuit can have so many perspectives. It's clearly a case where different
experience and background focuses attention on different details. (an
elephant by any other name, know what I mean).
My view of Nv logic:
Nv neurons are 2 input Wavefront processors which could be formally modeled
as Petri nets. More on this later.
wilf
> -----Original Message-----
> From: Jean auBois [SMTP:aubois@trail.com]
> Sent: Thursday, February 03, 2000 11:56 PM
> To: beam@sgiblab.sgi.com
> Subject: VSPANS (was: The 240 microcore - was: Bicore question)
>
> At 09:50 PM 2/3/00 -0800, Wilf wrote:
>
> >Here is a little thought experiment: in an open ended 6Nv (74HC14) chain
> >with LED indicators, what is the maximum number of processes (output low
> >pulses/LED on) that can be active at a time? I have not tried this but I
> >predict that if you try to "stuff" more that 3 processes in a 6Nv chain
> some
> >interesting things may happen.
>
>
> Well, I've always used the following really disgusting "solution" to this
> problem.
>
> Let's pretend two different (and actually quite conflicting) conditions
> exist at the same time. The first condition is that whatever signal you
> are stuffing into the chain is of a sufficiently high frequency that it is
>
> above the "knee" of the capacitor-resistor high-pass filter. At that
> point, there would be very little attenuation -- in other words, the
> capacitor-resistor portion of each Nv neuron would "disappear".
>
> The second condition takes the first for granted -- in other words, you
> still have a chain of six inverters but they are directly connected. In
> other words, they'd look like:
>
> in ----->o---a-->o---b-->o---c-->o---d-->o---e-->o----- out
>
> Pretending that we are using a D.C. level input, if in=high, then a=low,
> b=high, c=low, d=high and e=low. In other words, you'd see three
> low-active "processes" at a, c, and e. Likewise, if in=low you'd get the
> contrary state with three low-active "processes" at b, d, and out. So...
> the maximum number of processes is going to be three in a six Nv neuron
> chain.
>
>
> For what it is worth, I've tried this portion Wilf's experiment once upon
> a
> time. I applied a square wave to just such a six Nv chain (made out of a
> '14) and looked at the result on a dual-channel oscilloscope using the
> driving signal as the trigger. At a sufficiently low frequency, you'd
> stuff in a process and it would travel down the chain until it "fell off"
> the end. At a somewhat higher frequency, you'd see two processes
> somewhere
> in the chain. I then skipped a step, frequency/signal-wise 'cuz all I had
>
> was a simple signal generator -- two processes in such a chain can be
> separated by two or four inverters. Once I got above the "knee" however,
> every other inverter showed exactly the patter described in the previous
> paragraph until I got up to 1 Mhz which was the limit of the signal
> generator. This was well within the maximum switching frequency of the
> '14
> I was using, so I don't have a clue what happens if you go fast enough
> that
> it would make a difference.
>
> Interestingly, if it were a loop instead of a chain you'll notice that in
> both cases the output matches the input so such a loop ought to be stable,
>
> i.e. static. However, we really can't ignore the capacitor-resistor
> portions of the circuit so it can end up being -- under Really Bad
> Circumstances -- a very high-frequency oscillator which is only limited by
>
> the minimum switching time of the IC. I -think- that this explains the
> so-called super-saturated state that people report where all of the
> attached LEDs glow, but dimly & the IC gets very warm. Anyhow, the signal
>
> looks pretty high-frequency when you look at it on a scope and chips use
> more power / get warmer as the frequency gets higher.
>
>
> So... that's one possible clue into that part of the thought experiment
> even if my underpinnings are shaky. Nv-only chains only really show
> "interesting" behavior at relatively low frequencies. It reminds you of
> Tilden's earlier name "VSPANS" which (hoping I'm close here) stood for
> Very
> Slow Propagation Artificial Neuron (or nervous-net) Systems.
>
>
>
> jab
9820 Sat, 5 Feb 2000 19:06:03 -0500 Re: hc, hct, ac, act Dane Gardner
Check in the archive...I wrote a lengthy letter detailing the differences.
:)
Most Sincerely,
Dane
"It is my belief that nearly any invented quotation, played with
confidence, stands a good chance to deceive." -- Samuel Clemens (Mark Twain)
Insomniac's Dream
Robotics -- Electrical Engineering -- Home Brewing -- And More
I have visited many beam web sites, and each one suggests using different
chips. i'm wondering if anyone could clarify the differences between
74hc,
74hct, 74ac, and 74act. And i'm also wondering about the different
abilities
of the 74***14, 74***240, 74***244, and the 74***245.
az-anuxm
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