Alt-BEAM Archive
Message #13585
To: beam@sgiblab.sgi.com
From: turtletek@aol.com
Date: Mon, 17 Apr 2000 17:06:42 EDT
Subject: Re: Disappointment, not critics
I see what you mean, Sebastiaan. Although I agree that BEAM must take steps
to progress, I don't think that the area of advancement is being ignored.
Several people such as Ben and Wilf ( And Tilden too, I suppose 8) work in
the direction of a better, more advanced BEAM. Just because the rest of us
mostly just emulate designs, doesn't mean the technology is stale. Besides,
the high school geeks of today are the Mark Tildens of tomorrow. First we
copy, then we create.
Sorry if some of us, in an effort to "defend" the hobby, came off as
vicious. Sometimes I'm not surprised that Jim sees BEAM as a community were
opposing opinions are squashed.
-Brien the TurtleTek
www.extremesc.com/turtletek
13586 Mon, 17 Apr 2000 14:28:40 -0700 (PDT) RE: Disappointment, not critics beam@sgiblab.sgi.com Daniel Grace >I'm not trying to
> nit-pick, it's just
> that your point seems a bit reliant on BEAM and
> robotics being different.
Is a square and a rectangle different? The official
definition enabled all squares to be rectangles, but
not all rectangles are squares. This is like BEAM and
Robotics. I _think_ (I can't read his mind, of
cource), that he means that there is robotics, then
there is BEAM robotics. If it doesn't fit the BEAM
philosophy, don't call it BEAM, call it a robot.
~Daniel
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13587 Mon, 17 Apr 2000 18:22:47 EDT Re: Walker competitions beam@sgiblab.sgi.com BUDSCOTT@aol.com Okay, just checkin up on ya! I hope things start to lighten up on you, sounds
like your pretty busy. What were the walker competitions like in previous
years, just legged races? Anyways thanks! C'ya
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13588 Mon, 17 Apr 2000 18:26:22 EDT Re: reverser beam@sgiblab.sgi.com BUDSCOTT@aol.com I ALWAYS use a ALS245 for a motor driver, it's too simple to pass up! Heck, i
even understand how it works!
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13589 Mon, 17 Apr 2000 17:01:14 -0600 Try building a robot that tries to avoid getting stepped on. beam@sgiblab.sgi.com "John A. deVries II" Was Mr. Robinson's challenge. Ben Hitchcock replied:
>Female chickens will stoop down whenever a shadow falls over them, because
>they think that a rooster is about to mate with them. A shadow cast by a
>human works just as well as a rooster. I wonder just how 'sure' a robot
>needs to be?
His last sentence, I think, is a real clue to the situation. Wandering off
thinking about various technologies is not necessarily the right place to
start with this challenge.
Firstly, there isn't a really good definition of "environment", "avoid",
or, for that matter, "being stepped on". Granted, everyone might rush to
say that at least the latter is obvious -- the robot should not be stepped
on by a person. If you didn't want cockroaches stepping on your robot, or
your family cat, or the elephant in your back yard you've got a huge range
of scale. Be that as it may, let's say that the robot is supposed to
behave in such a manner as to avoid being stepped on by a person.
Well, what does that take? What behaviors are involved? The aggressive
manner has been suggested but actually fails -- so what if someone gets
lots of needles in their foot (silly person!)? They still have stepped on
the robot.
I think that the behavior that best fits the situation would be for the
robot simply to Not Be There when a foot comes down. The truly bizarre
imagination might think of "BEAMing" the robot (sorry, just couldn't avoid
the pun) somewhere else, but we don't know how to do that yet. Thus we are
left with physical motion, using legs or wheels or whatever. In any case,
the robot is more-or-less forced to stay on the surface (of wherever it is)
unless it has a decent early warning system and could fly away before the
foot actually got close. However, this "closeness" would be hard to define
-- just as Ben writes, "how 'sure' a robot needs to be"? Generally
speaking, the early warning method would cause the robot to flee from ANY
change in its environment presuming it could figure out the direction of
the change and this is pretty wasteful of energy.
Jonathan Connell, who was Rodney Brook's student something like twelve
years ago, came up with something he called a "photovore" (a teensy bit
earlier than the BEAM phenomenon, I think.) You can wander off to his site
http://www.pcrealm.net/~johuco/photov.html
and buy an entire kit; you could
also read about Richard Hughes' modification of the device
http://members.aol.com/rich924/html/vore.html.
The cool thing about this
photovore is that it had a light sensor pointing _up_ as well as the usual
two facing "forward".
Using just a little bit of digital logic (rather similar to what I was
talking about in that other huge note way back when) Jon was able to come
up with a behavior that is very nearly a solution to Bruce's challenge. If
the top sensor "saw" light then the photovore worked just as you would
expect, moving toward light. On the other hand, if the top sensor
'suddenly' was in the dark a new behavior would take over (subsuming the
light chasing behavior, by the way). The photovore would do its best to go
ANYWHERE quickly, but the ANYWHERE depended on the front sensors -- it
would do its best to avoid the dark, "presuming" that darkness meant an
obstacle.
As a result, when the Deadly Darkness approached from above, the robot
might zoom straight forward, spin left or right in place until it found a
"good" place to run and then scoot or even simply zoom straight backwards.
So... with the addition of a single sensor and a teensy bit of digital
logic the robot was enormously more "adept" than a simple photovore.
Zoz
13590 Mon, 17 Apr 2000 19:23:58 EDT Re: Try building a robot that tries to avoid getting stepped on. beam@sgiblab.sgi.com turtletek@aol.com
My first thought, "Neat, let's BEAM-ify it!", was followed shortly afterwards
with my second thought "How?". What qualifies to me as a BEAM bot is a solar
powered one. However, how would a photovore designed with the errm..MIT
photovore in mind get the power needed to bolt at the sign of danger? Here is
where it gets BEAMish.
I haven't built a bot around the Chloroplast SE yet but it is my
understanding that it allow the use of much larger, ineffiecient and much
more torque-y motors on photovores. This could provide the torque needed for
a quick acceleration. What about the power needed?
I know there is some kind of fat storage cap circuit around that allows a
robot to charge a large cap and keep it in reserve until it meets the proper
environment (in this case, overhead shadows) and it discharges into the
motors for a quick, if not very prolonged, burst of speed.
All right then, all done chewing the fat.
-Brien the TurtleTek
13591 Mon, 17 Apr 2000 19:27:55 EDT REVERSER, Again! beam@sgiblab.sgi.com BUDSCOTT@aol.com I've got my two bicores hooked up so that there is a reverser that will
reverser just the front motor, the reverser is hooked up to a ALS245 motor
driver, and the reverser is the 240 chip with the 47k resistors across the
inverters, BUT for some reason, the front motor will only run when the thing
is reversed! What's up with that?
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13592 Mon, 17 Apr 2000 16:31:25 -0700 Photopopper tactile sensors... "Beam" "Gabriel DeVault"
Hello all,
I've finished a phtotopopper recently (ala chiu style). I'd like to put tactile sensors on it. I think I have a method that is
easier to implement than any of the designs I've seen. Use standard tactile sensors and have them simply short the photodiode on the
appropriate side. I tested this on my current photopopper and it seemed to work fine. Any feedback?
Thanx, Gabe
http-equiv=3DContent-Type>
Wilf Rigter But is a 74ALS245 compatible with Ian's reverser? Have you tried a
74AC/ACT245? Afaik it provides more current and consumes less power.
wilf
> -----Original Message-----
> From: BUDSCOTT@aol.com [SMTP:BUDSCOTT@aol.com]
> Sent: Monday, April 17, 2000 3:26 PM
> To: beam@sgiblab.sgi.com
> Subject: Re: reverser
>
> I ALWAYS use a ALS245 for a motor driver, it's too simple to pass up!
> Heck, i
> even understand how it works!
>
> -Spencer
>
> <http://www.botic.com/users/beamstop>
>
> not a robot scientist
> not a college major
> not a grad student
> not a professor
> not a very organized person
> just Spencer (isn't that impressive enough?)
13594 Mon, 17 Apr 2000 19:55:13 EDT Re: REVERSER, Again! beam@sgiblab.sgi.com SkavenArmy@cs.com i am suprised that as evolved as the beam community is , theres not many
different kinds of bots...theres weelers , walkers and (no pun intended)
vibrators.youd thhink that by now,wed have fliers,sliders,pullers,swimmers. i
understand that im expecting(or hoping) us to cram 5 bilion years of
evolution into a one month period of internet discussions.
new idea: i have an empty irx(pirate irc) ip address. ill configure it if
ya'll want a beamnet.
jay z
13595 Mon, 17 Apr 2000 19:56:55 EDT Re: Photopopper tactile sensors... beam@sgiblab.sgi.com SkavenArmy@cs.com bro:that is wicked!
sorry this is so stupid, but that is soooooooooo wicked!
jay z
13596 Mon, 17 Apr 2000 19:57:21 -0400 RE: Deadman's stick (was: RE: Monitor Salvage) beam@sgiblab.sgi.com "Terrance (Terry) G. Bondy" I've taken apart many TV's. The only precautions that I took was to make
sure that it was not plugged in a week or so before you started working on
it. TV repair shops don't have that luxury - time is money.
Terry
At 01:19 PM 4/17/00 -0700, you wrote:
>John's description of the "deadman's" stick is correct: the wooden dowel
>acts as an insulated handle and should be held at one end with the resistor
>and pin secured to the opposite end.
>
>The CRT anode capacitance behaves just like a Leyden jar (the world's first
>capacitor). The anode lead connects to a terminal on top of the CRT through
>the glass envelope to the metalization on the inside and face of the CRT. A
>rubber suction cup covers this connection to the CRT anode terminal. The
>metalized outside of CRT is grounded to the chassis ground using contact
>fingers or a spring tensioned bare wire in contact with the CRT. The CRT
>capacitance filters the dc voltage on the anode generated by the horizontal
>flyback transformer and rectifier assembly. The anode voltage depends on
>the size of the CRT and can be as high as 30,000 Volts. The remaining charge
>on the CRT anode can be quietly discharged through a >1M resistor to ground
>using a well insulated "deadman's stick". Before discharging, the monitor/TV
>MUST be unplugged from the AC power supply and always FIRST connect the
>grounded side of the discharge resistor to a suitable place on the
>chassis/frame before touching the other side of the resistor to the "hot"
>terminal of the cap. For a CRT anode, the hot terminal is the metal contact
>under the suctioncup on top of the CRT at the end of the anode lead. The
>deadman's stick has a stiff pin on the end which can slide under the suction
>cup and discharge the CRT.
>
>regards
>
>wilf
>
> > -----Original Message-----
> > From: John A. deVries II [SMTP:zozzles@lanl.gov]
> > Sent: Monday, April 17, 2000 10:37 AM
> > To: beam@sgiblab.sgi.com
> > Subject: Deadman's stick (was: RE: Monitor Salvage)
> >
> > I seem to remember a tool that TV/radio repair types used to have or make
> > for themselves called a deadman's stick. Basically, it was a stick of
> > wood
> > (a dowel would work) that is about a foot long with a pin stuck in one
> > end. Someplace close to the pin you'd tape a 1M ohm resistor and connect
> > it to the pin with some wire and then run another piece wire back up the
> > stick. Of course, where you soldered on both sides of the resistor you'd
> > put a fairish amount of electrical tape -- I suppose the PVC stuff they
> > sell these days would work. The wire that was on your side of the
> > resistor
> > would be perhaps two feet long (depended on how big the equipment was that
> >
> > you worked on) and you'd solder an alligator clip onto it. Chances are
> > you'd want to have one of those alligator clips that has the plastic
> > shroud
> > -- some of us can be fairly clumsy when hooking it to one side of a cap
> > (which could be a pain if the other side was connected to something that
> > another part of your hand touched.)
> >
> > Anyhow, you'd then attach the alligator clip to some part of the chassis
> > that was obviously grounded or one end of some component you wished to
> > discharge and you could go poking around (one hand in your pocket, as they
> >
> > say) to discharge capacitors and the TV tube itself (which acts as a HUGE
> > capacitor -- they don't put those warning signs on for jollies and the
> > charge can stay on it for many many months). When you probed a particular
> >
> > connection, you held it there for a while to make sure that the thingy you
> >
> > were discharging was really dead.
> >
> > Now, what I don't remember exactly is how one discharges a TV tube...
> > Wilf??
> >
> > <----------=========---------------K
> > pin resistor alligator clip
> >
> >
> > Zoz
> > Someone who has picked up a live monitor chassis and still remembers how
> > much his arm hurt afterwards. Thank God it was low current!!!
----------------------------------------------------
Terry Bondy | Ph: 1-905-830-1032
760 Sunnypoint Dr. | e-mail: bondys@netrover.com
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