Alt-BEAM Archive
Message #12644
To: beam@sgiblab.sgi.com
From: "Timothy Flytch" flytch@hotmail.com
Date: Tue, 28 Mar 2000 01:06:44 PST
Subject: [alt-beam] Re: Online robot simulator software
I love it!!! I don't understand it yet but I think I have a new toy for
awhile :)
Thank you, Thomas...
Timothy...
>From: "Thomas Pilgaard"
>Hiyall,
>
>I've stumpled upon this quite amusing online construction program for
>walking creatures and thought I'd share it with you. It's rather primitive
>in graphics, but it offers the possibility of creating muscles and a number
>of configurations are possible.
>
>Have a look at:
>
>http://www.soda.co.uk/soda/constructor/index.htm
>
>Cheers,
>
>Thomas
>
______________________________________________________
12645 Tue, 28 Mar 2000 23:18:29 +1000 [alt-beam] FRED tutorial beam "Ben Hitchcock" All,
Due to popular demand, I have made a FRED tutorial. The response to the
FRED circuit has been quite overwhelming! I originally made it because
someone on the list said that you couldn't make a photopopper with a FLED
solar engine - and I'm a stubborn guy who refuses to believe anything unless
it is proven to me in words of one syllable! Anyway, here's the address:
http://wollongong.apana.org.au/~ben/fredtute/
Enjoy!
Ben
12646 Tue, 28 Mar 2000 07:58:11 EST [alt-beam] Re: Allmost complete walker. still not working beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 3/27/00 4:37:18 PM Eastern Standard Time, BUDSCOTT@aol.com
writes:
> maybe
> you'll find out whats wrong, my guess is that your linking resistors are
out
>
> of whack.
Yep, sounds right to me. I had the same problem with Ambler in the beginning.
At start up, it would go through one cycle. Then, the master would stop
moving and the slave would begin oscillating wildly. Racked my brain over it
several times. Finally, I did the old stand by. I started resoldering all
connections. When I got to the biasing resistors, it straightened up and
walked like a charm. Ambler uses a different circuit, but a Bicore by any
other name would oscillate just as sweetly :).
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
12647 Tue, 28 Mar 2000 08:01:51 EST [alt-beam] Re: Challenge? Online robot simulator software beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 3/27/00 6:11:27 PM Eastern Standard Time, zozzles@lanl.gov
writes:
> Can
> anyone imagine making shock absorbers for a BEAM robot?
I just posted one Zoz. Did you miss it? I've been using them in Carbots for
some time. Ambler is my first use of them in a walker, with many more to
come. You should check out my work every now and then.
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
12648 Tue, 28 Mar 2000 08:34:58 PST [alt-beam] Re: 1 Amp H-bridge beam@sgiblab.sgi.com "sebastiaan van Vliet"
>From: SG
>Reply-To: beam@sgiblab.sgi.com
>To: beam@sgiblab.sgi.com
>Subject: Re: 1 Amp H-bridge
>Date: Sat, 25 Mar 2000 14:29:06 -0600
>
>euh.. they just can pull 1 amp. I use 4 AAA zized batteries
>one amp?
>are you sure about that?
>from what size battery?
>thanx
>-Sparky
>At 11:09 AM 3/27/00 PST, you wrote:
> >
> >I made mysel a niceworking H-bridge from BC 639 & BC 640 transistors. Has
> >this been done before? I is said to deliver 1 amp of power!
> >______________________________________________________
> >Get Your Private, Free Email at http://www.hotmail.com
> >
> >
>
______________________________________________________
12649 Tue, 28 Mar 2000 11:43:54 -0500 [alt-beam] Re: Charging NiCads beam@sgiblab.sgi.com "Sathe Dilip" For a normal charging cycle, charge them for about 14 hours at 1/10th of
the Ampere-Hour capacity.
In your example, charge at 60 mA for 14 hours. If your batteries are
rated for a fast charge, you can charge them with more current with a
proportionately less time.
Dilip
---------------------------------
Andrew Hooper wrote:
> Been a long time since I built my last charger, and I cant remember
> what the rule of thumb was in regards to voltage and current.
>
> The pack I have consists of 4 X 1.2v 600ma cells in series.
>
> Any ideas or thought?.
----------------------------------------------------------------------
The early bird may get the worm, but the second mouse gets the cheese.
----------------------------------------------------------------------
12650 Tue, 28 Mar 2000 08:38:50 PST [alt-beam] thanks spencer beam@sgiblab.sgi.com "sebastiaan van Vliet"
thanks for your help on the walker circuit!
______________________________________________________
12651 Tue, 28 Mar 2000 08:42:18 PST [alt-beam] Re: Allmost complete walker. still not working beam@sgiblab.sgi.com "sebastiaan van Vliet"
>From: "Jim Taylor"
>Reply-To: beam@sgiblab.sgi.com
>To:
>Subject: Re: Allmost complete walker. still not working
>Date: Sun, 26 Mar 2000 17:35:50 -0500
>
>what are your resistor values?
>
Just the same as on Ians page. Maybe you could help me with this one: How do
I turn down the frequency of the bicore? Somebody advised me to replace the
ones on the side, but they only seem to influence the delay between the
master ans the slave.
> >
> >
>
______________________________________________________
12652 Tue, 28 Mar 2000 09:13:52 -0800 (PST) [alt-beam] Piezo vs. Transducer beam@sgiblab.sgi.com Lee Golden Could someone please give a quick rundown on the
difference between a Piezo speaker and a tone
transducer? I am getting ready to turn my entire
paycheck over for some parts, and I want to pick up a
few things for a BEAM audio circuit. I have tried to
discern the differences, but the only thing I have
read is that some transducers require both a power
source AND a signal source to generate sound.
Help! :-)
Lee Golden
http://www.geocities.com/leemon1/Bots/beambots.html
__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
http://im.yahoo.com
12653 Tue, 28 Mar 2000 09:59:00 PST [alt-beam] Re: Allmost complete walker. still not working beam@sgiblab.sgi.com "sebastiaan van Vliet"
>From: JVernonM@aol.com
>Reply-To: beam@sgiblab.sgi.com
>To: beam@sgiblab.sgi.com
>Subject: Re: Allmost complete walker. still not working
>Date: Tue, 28 Mar 2000 07:55:02 EST
>
Thanx for the help. The linking resistors, are those the ones on the side or
the diagonal placed ones? Ans what is the blue one?
>In a message dated 3/27/00 4:37:18 PM Eastern Standard Time,
>BUDSCOTT@aol.com
>writes:
>
> > maybe
> > you'll find out whats wrong, my guess is that your linking resistors
>are
>out
> >
> > of whack.
>Yep, sounds right to me. I had the same problem with Ambler in the
>beginning.
>At start up, it would go through one cycle. Then, the master would stop
>moving and the slave would begin oscillating wildly. Racked my brain over
>it
>several times. Finally, I did the old stand by. I started resoldering all
>connections. When I got to the biasing resistors, it straightened up and
>walked like a charm. Ambler uses a different circuit, but a Bicore by any
>other name would oscillate just as sweetly :).
>
>See ya,
>Jim
>http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
>ICQ# 55657870
______________________________________________________
12654 Tue, 28 Mar 2000 10:27:30 -0800 [alt-beam] Re: 2nd - Reverser drawing - attn. Bruce beam@sgiblab.sgi.com Bruce Robinson Ken Hill wrote:
>
> Bruce, could you elaborate on the "fry it" part?
> (or direct me to a suitable link maybe?)
The 6 transistor Tilden H-bridge cannot have both inputs "on" at the
same time. If this happens, you will get a direct short through the both
sets of power transistors, which is kinda like creating a high-wattage
heating element :)
The problem then, is what represents an "on" condition. The free-form
layout of this circuit shown at BEAM-online is a "positive logic"
circuit (on = positive input), so you never want both inputs to be
positive at the same time.
The 74xx139 chip has inverted outputs: the outputs are are considered to
be "off" when they are high (positive), and "on" when they are low. This
means the "don't run the motor" output from this chip has two postitive
outputs. Connect that to the H-bridge shown at BEAM-online, and you will
instantly short out your transistors.
The solution (as described in Tilden's paper) is to make a "negative
logic" H-bridge by swapping a couple of transistors and reversing their
direction.
> The '139 use I refered to is the Z-drive in the Beam Tek's - motor
> drivers paper. Mark later mentions that the ACT version works
> well for this purpose ...
The Z-drive simply omits the H-bridge and used the 74xx139 to drive the
motors directly. Bram van Zoelen's original idea was to use
higher-current chips and overload them briefly, giving a drive
capability of 100 mA, about the same as the BEAM-online H-bridge.
Mark Tilden was obviously taken with the simplicity, and suggested using
the ACT chip family to allow higher currents while drawing less power.
As he points out, the chips can be stacked to get even higher current
handling ability. He tested this design up to 300 mA, which is quite
respectable.
> ... but you should have a "47k pull-down resistor for all enables
> and A & B inputs." Would that be "down" to ground or just in series
> with the enables/inputs?
"Pull-down" means connect the inputs to ground; "Pull-up" means connect
the inputs to Vcc. It's never a good idea to leave an input free to
"float" (even if you aren't using the input).
The pull-down resistor Tilden suggests will effectively connect the
input to ground if it isn't receiving a signal. A positive input will
over-ride the resistor, but there will be a small current loss through
the resistor. A 47k resistor with a 5 volt supply is only going to draw
0.1 milliamps so it's not normally a big deal.
> Terms like this, and positive edge, and positive logic, etc. are a
> gray area here.
Positive edge = a shift from low voltage (ground) to high voltage (Vcc).
The typical Nv triggers on a positive edge. Also describe as "rising
transition", "high-going", etc.
Positive logic means a positive signal represents the "on" or "active"
condition. Negative logic means a negative (GND) siganl represents the
"on" or "active" condition. Usually :) It's not always precise
terminology.
Bruce
12655 Tue, 28 Mar 2000 10:39:44 -0800 [alt-beam] Re: Piezo vs. Transducer beam@sgiblab.sgi.com Bruce Robinson Hi, Lee.
Only a partial answer, I'm afraid.
When I was helping Sparky debug his cricket circuit, we ended up sifting
through half a dozen circuits he'd found (most of them with serious
bugs). It took us a while before we figured out that there were two
types of "piezo" devices: with one type, you had to provide a signal
(e.g. audio frequency) to make the device work. With the other type, you
just had to supply power ... the frequency generator was built into the
circuit.
The first type means you have the extra work of providing signal
circuitry, but you have control over the tones it generates. And of
course, if you want to use it as an actual speaker, this is the kind you
need.
The second type is utterly simple, but you're pretty much stuck with
whatever tone it produces. It's definitely not the one you want for an
actual speaker.
It was easy enough to tell which one Sparky had (once we figured out
there were two types). He just applied a little battery power directly
to the inputs (the first type will "click", the second type will buzz,
humm, screech, whatever).
Sorry I don't have the correct terminology for these; hope this gives
you some idea of the differences.
Bruce
12656 Tue, 28 Mar 2000 11:08:01 -0800 [alt-beam] Re: 2nd - Thanks Bruce (no message) beam@corp.sgi.com Ken Hill
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