Alt-BEAM Archive
Message #11771
To: beam@sgiblab.sgi.com
From: Dave Hrynkiw dave@solarbotics.com
Date: Mon, 13 Mar 2000 22:47:07 -0700
Subject: [alt-beam] Re: H-Bridge
At 09:53 PM 3/13/00 , Andrew Hooper wrote:
>I have been looking at several H-Bridge circuts (as the Zetex chip is not
>readily avalible over here)
>and found that there is a 6 transistor and a 4 transistor version, both seem
>to be no smoke.
>
>What are the bonuses or drawbacks of using these?
Little if no drawbacks. Although the Zetex chip is a tidy package, don't
let that keep you from trying your own "free-hand" H-bridge. beam-online
has a bit of a layout to get you started. And I FULLY recommend you use
2n2222 for 3904's and 2907 for 3906's, as once (quite forcefully and
accurately!) pointed out by Steven Bolt. Much better, for pennies more a
transistor.
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
11772 Mon, 13 Mar 2000 22:44:34 -0700 [alt-beam] Re: Interesting, ain't it? beam@sgiblab.sgi.com Dave Hrynkiw At 08:35 PM 3/13/00 , Ben Hitchcock wrote:
> > Here we are meeting people across the void of cyberspace and out of the
>40 or so million people using the net, I end up on a small list of robot
>enthusiasts (considered outcasts and fools by the establishment) and two
>others have read that story! Gives one pause to think about coincidence
>and it's function in the universe...
>
>
>Make that three!
Try four, but I didn't recognize the title until you described the
plot-line. Guess Sci-Fi is what tech-heads are drawn to in the
off-robot-hours, hmmm? "Day of the Triffids" is one of my faves tho. And
nothing has topped "Ender's Game" yet, although the new "Ender's Shadow" is
a very good read. THOROUGHLY GOOD READS, all of them.
-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
11773 Mon, 13 Mar 2000 22:43:12 -0700 [alt-beam] Re: scoutwalker2 details beam@sgiblab.sgi.com Dave Hrynkiw At 08:56 PM 3/13/00 , StickG@aol.com wrote:
>I know some people have been privileged to build one of these kits at
>workshops and stuff, could someone tell my how it's wired (I understand
>bicores and all that), but more like, how does it hook up to the MUX and how
>are the sensors inputed and so on, please! I'm building a five motor, and I'm
>sure any info would help!
>also, does one 74AC240 chip have enough power to drive one of those tower
>servos?
The schematic for the "MattMux" is at
http://www.beam-online.com/Robots/Circuits/circuits.html
under the
"Reverser" heading. Another clever circuit designed in part by one of Mark
T's Grad-students (thus the "Matt"). In short, it depends on the
high-impedence characteristics of the inputs to the 240. It operates as a
normal buffered gate, with the 47k resistors looking (essentiall) like
shorts (well, to a system using MEGAOHM resistors, 47k is pretty
insignificant). When the enables get toggled, the 47k resistors are
"over-ridden" by the buffered, REVERSED signal through the chip.
A single AC240 does a great job of driving a modified tower hobby servo.
Splendidly, almost too much power when using a solid 6V source.
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
11774 Tue, 14 Mar 2000 00:40:22 -0600 [alt-beam] Re: numeric symbol for a .1pf ceramic cap beam@sgiblab.sgi.com Richard Piotter Thanks for that info. I knew that one page had incorrect instructions.
I'm glad it's working for you! Great job finding the calc's limits as well!
I should look into interfacing a Calc, a BASIC Stamp, and an Nv/Nu net
system. Then I can justify that massive robotics section on my TI web
page! Hehe! :)
Jim Taylor wrote:
>
> Hey rich a little update on my turbo ti83 mod. It works, but it took some
> tinkering with values. I've gotten as low as 10pf, and as high as 47pf.
> Currently I'm running a 15 pf cap on a switch with the original cap.
> Everthing is working great. It is noticably faster, however I have no
> concrete way of testing clock speed.
> By the way I think you were correct, the TI page I was looking at was way
> off on the mod. The .1pf cap caused some nasty results on the LCD end,
> which I was told; is normal when an 82, or 83 is accelerated beyond it's
> limit of sorts. The correct cap to replace was also incorrect. It is
> supposed to be C7.
>
> Thanks for your help
>
> James Taylor
> "Edgar The Hate Bug"
> URL: http://fly.to/springmeadows
> ICQ 14888587
> ----- Original Message -----
> From: Richard Piotter
> To:
> Sent: Tuesday, February 29, 2000 3:00 PM
> Subject: Re: numeric symbol for a .1pf ceramic cap
>
> > I was thinking 1pf. I spoke before (direct mail). The .1pf instructions
> > were from a web page that was hastily written, and does not follow the
> > standard procedure for turboing calculators. a .1pf cap isn't even
> > needed. As said before, wire and such can do the same task, for that
> > particular upgrade anyway.
> >
> > Of course, Radio Shack don't sell .1pf caps. I was going bby memory of
> > the original upgrade plans, that calls for a 1 pf. Oops.
> >
> > John Bachman wrote:
> > >
> > > At 10:42 AM 2/29/00 , you wrote:
> > > >Not avaliable my foot! Even Radio Shack sels them!!!
> > >
> > > The question was about a 0.1pf. That is an order of magnitude from 12pf
> or 15pf or 8pf.
> > >
> > > John
> >
> > --
> >
> >
> > Richard Piotter The Richfiles Robotics & TI web page:
> > richfile@rconnect.com http://richfiles.calc.org
> >
> > -- Make Money by Simply Surfing the Net or responding to E-Mail!!!
> > -- Click below!!!
> >
> > http://www.alladvantage.com/go.asp?refid=ATL147
> > http://www.spedia.net/cgi-bin/dir/tz.cgi?run=show_svc&fl=8&vid=329630
> >
--
Richard Piotter The Richfiles Robotics & TI web page:
richfile@rconnect.com http://richfiles.calc.org
-- Make Money by Simply Surfing the Net or responding to E-Mail!!!
-- Click below!!!
http://www.alladvantage.com/go.asp?refid=ATL147
http://www.spedia.net/cgi-bin/dir/tz.cgi?run=show_svc&fl=8&vid=329630
11775 Mon, 13 Mar 2000 23:19:12 -0700 [alt-beam] beam database place beam@sgiblab.sgi.com Jean auBois
>skeleton idea, someone good at html could make a basic, tree-structured
>website
>Yes Perl and SQL work well together, I have a server located in the US its
>sole purpose is for web hosting and serving up dynamic web pages.
Kindly look at http://www.discusware.com/discus/
A certain not-to-be-named site has been using the freeware version
for two years and does exactly what you are describing although it doesn't
use SQL
Home