Alt-BEAM Archive

Message #13694



To: beam@sgiblab.sgi.com
From: SkavenArmy@cs.com
Date: Wed, 19 Apr 2000 20:31:19 EDT
Subject: Re: Best solar panel supplier?


i found the homemade solar panels that even though they are bulky , that once
refined , they work great(better than my store bought.) they are the ones
from the electrochemistry page in one of the links someone sent out a lot
erllier on in the list



jason zink



13695 Wed, 19 Apr 2000 20:36:45 EDT Re: efficient launcher? beam@sgiblab.sgi.com SkavenArmy@cs.com DUCK!~



13696 Wed, 19 Apr 2000 17:44:13 -0700 RE: Dummy Walker "'beam@sgiblab.sgi.com'" Wilf Rigter Ooops! Obviously you were way ahead of me on the reverser, since you
described one method that actually works in detail.
But I'll contribute something yet.

regards

wilf

> -----Original Message-----
> From: Ben Hitchcock [SMTP:ben@wollongong.apana.org.au]
> Sent: Wednesday, April 19, 2000 6:51 AM
> To: beam
> Subject: Dummy Walker
>
[Wilf Rigter] ----8<----

To reverse the gait you
have to move the inverter from the top (that is pointing left), and put it
in between the other two inverters, pointing right. This means that you
have to do away with the pairing of the two servo motors being fed from the
one set of drivers. In other words, you use eight driver gates instead of
six.


> Ben



13697 Wed, 19 Apr 2000 17:49:07 -0700 RE: Dummy Walker "'beam@sgiblab.sgi.com'" Wilf Rigter Let me describe the logic of this mechanical feedback with hysteresis system
which is a kind of mechanical Nv neuron bicore.

First take the case of one motor. The reciprocating left - right logic
depends on negative feedback from the motor pot. With negative feedback, the
motor driver reverses when the output voltage from the pot crosses the
Schmidt trigger threshold effectively limiting travel in that direction.
Reversing the phasing of the motor of the pot changes the feedback from
negative to positive! Now the opposite effect takes place as you find out
with that 50% chance of wiring the motor or the pot the wrong way. With
positive feedback the motor is driven hard against the left or right
mechanical stops with the logic encouraging the attempt to strip the gear
box. What to do? Well you have a choice, reverse the motor or the pot
connections and you restore negative feedback.

The Dummy Walker has 2 motors and these interact in an interesting
non-intuitive way

Let me describe the combinational logic for the dummy walker pattern
generator.

If the output logic state of the servo pot position sensing Schmidt Triggers
(ST1 and ST2) is either +1 (high) or -1 (low)

then motor M1 direction is the sum of the ST1 and ST2 outputs

if ST1 plus ST2 = +2 then M1 LEFT (L)
if ST1 plus ST2 = 0 then M1 STOP (S)
if ST1 plus ST2 = -2 then M1 RIGHT (R)

and M2 motor direction is the difference of ST1 and ST2 outputs

if ST1 minus ST2 = +2 then M2 LEFT
if ST1 minus ST2 = 0 then M2 STOP
if ST1 minus ST2 = -2 then M2 RIGHT

ST1 and ST2 change to state at the end of left or right travel and cannot
change state when the servo is stopped.

The following sequence table should hold:

ST1 +1 +1 -1 -1
ST2 -1 +1 +1 -1
M1 S L S R
M2 L S R S

The sequence points out that M2 leads M1 by 90 degrees which is the forward
mode.

Next M1 leads M2 = reversing !

wilf

> -----Original Message-----
> From: Ben Hitchcock [SMTP:ben@wollongong.apana.org.au]
> Sent: Wednesday, April 19, 2000 6:51 AM
> To: beam
> Subject: Dummy Walker
>
> Well,
> Questions, comments?
>
> Ben



13698 Wed, 19 Apr 2000 22:02:48 EDT Re: efficient launcher? beam@sgiblab.sgi.com Meabadboy@aol.com In a message dated 4/19/2000 5:14:24 PM Eastern Daylight Time,
phillip@ryals.com writes:

> Actually, you're right, this would rock. The only problem is I'd like it to
> be able to reuse the hook. So that it would launch, retrieve, load,
launch.
> That, and potato guns scare me. :) Actually, they're fun as can be, I've
> just heard too many stories.


well as with anything ~ SAFETY and good engineering is a must ~ the STORIES
you hear are from those whom were foolish ~

I thought further on my flight today about that idea ~ i hate Delta ~ anyway
~ i believe that a good source of fuel would be a lighter fluid ~ a little
goes a long way ~ it is light weight and vaporizes quickly ~ with the potato
gun ~ you want to allow the fluid to completely turn to a vapor to ignite and
achieve a proper amount of force ~ the attache sketch was only a quick
diagram ~ it would need some experimentation ~ not to mention finding the
right fuel/air mix as not to produce too much kick and turn over the bot ~
but enough to launch the grapple a sufficient distance.

one could meeter the amount of fluid for different distances baised on some
sort of sonar sensor reading ~ i know a little out of the BEAM relm because
it usually requires a microprocessor to make a sonar sensor work efficiently
~ however who said a sensor couldnt be a seperate package as a sonor sensor ~
microprocessor ~ and then provide an output to the beam circuit?

steve

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