Alt-BEAM Archive
Message #11318
To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Fri, 3 Mar 2000 07:35:04 -0800
Subject: [alt-beam] Re: Current draw questions...
Hello Richard,
In the end, it is total system efficiency that counts but to be able to =
rank
each major component in the system you need to make that component an
independent variable. So for testing the comparative efficiency of =
motors to
be used in an SE controlled wheeled robot, you could connect a simple
simulated load to the motor (ie a suitable fly wheel). Then charge a =
fixed
size cap (ie 4700 uf) to a fixed voltage (ie 3V or 4.5V) and use a =
simple
toggle switch to apply this fixed energy in the cap to the motor. Now =
count
the number of revolutions of the flywheel per capacitor discharge and =
you
get a numerical value you can use to compare with another motor.=20
Using a flywheel load attached directly to the motor shaft is a =
reasonable
approximation of the inertia of a wheeled robot but eliminates other
efficiency factors in the drive train (ie traction/friction) that can =
affect
overall performance. The fixed cap charge simulates an SE controller =
and the
toggle switch eliminates losses in the SE driver transistors.=20
To test the SE efficiency, you can use a similar arrangement but =
substitute
an SE for the toggle switch. With a fixed light source and sockets for
various SE components you can substitute and measure the effect on the
number of flywheel rotations per unit time=20
(ie total revolutions in 10 minutes). Adding a photo-interrupter and =
simple
counter circuit can automate part of the process and prevent going =
cross
eyed counting turns.
To test solar cell efficiency, use the same setup and try various light
levels or substitute solar cells.
Such a setup can provide reasonably controlled conditions for ranking =
the
efficiency of various components in a robot system.
Once the best components have been selected they must be tested in a
complete system in a typical environment (ie the real world) where some
factors (ie some magical coupling coefficients) come into play.
regards
wilf
=20
=20
> -----Original Message-----
> From: Richard Caudle [SMTP:richard@cqc.com]
> Sent: Thursday, March 02, 2000 6:42 PM
> To: BEAM
> Subject: Current draw questions...
>=20
> E'en all (anon)!
> =A0
> Whilst testing my little HPV Board, I decided to do an Amp test to =
gage
> the efficiency of my motors.=A0 I took the reading from the =
capacitor.=A0 Is
> that the reading for the entire circuit, or is it just the cap's =
amperage?
> =A0
> Richard Caudle
> www.geocities.com/frankendaddy =
<http://www.geocities.com/frankendaddy>
> Home ICQ - Frankendaddy
> _____ =20
>=20
> Guardians of the sacred words: Nee, Ptang, and =
NeeWhon!=A0=A0=A0=A0=A0=A0=A0=A0=20
11319 Fri, 03 Mar 2000 12:40:19 -0500 [alt-beam] Re: photoresistors beam@sgiblab.sgi.com "Sathe Dilip"
Bruce Robinson wrote:
>
> William Cox wrote:
> >
> > Does any body have a schematic for a phototropic head
> > or ant that uses photoresistors instead of diodes?
>
> Here's one that has worked well for me. The photoresistors are the ones
> to the right of the 1 meg resistors.
>
I think the standard symbol for a photo resistor is a simple resistor
enclosed in a circle (sometimes I have seen people use an ellipse) and
the greek symbol Lambda (looks like inverted Y) by the side of the
resistor (within the circle). This is just fei (for everybody's info).
Dilip
----------------------------------------------------------------------
The early bird may get the worm, but the second mouse gets the cheese.
----------------------------------------------------------------------
11320 Fri, 3 Mar 2000 11:49:00 -0600 [alt-beam] Futaba servo motors "'beam@sgiblab.sgi.com'" "Vermeulen, Vincent" Anyone worked extensively with Futaba S28's servo motors. I just built my
first 2 motor walker, but want to make sure that these motors are decent or
if other ones are better.
Thanks,
Vincent
11321 Fri, 3 Mar 2000 11:52:14 -0600 Re: My walker ain't walkin' beam@sgiblab.sgi.com Bruce Robinson [mailto:Bruce_Robinson@telus.net]
BUDSCOTT@aol.com wrote:
>
> i just finished *whew* my first walker, ...
> ... the motors occilate, but the bot looks as if its doin a @#$&in'
> mating dance! What should i try ...
Check the balance. If the weight is too far to the front or to the back,
it will tend to dance around in one spot. Ideally you want the center of
gravity to be midway between where the feet touch the ground. The shape
of the legs don't matter (as long as they don't bash the 'bot), it's
where the feet are placed.
> ... i'm gonna put motor stops so the ...
Richard's right on about the stops. Simple contact switches to cut the
delay are what you want with high gearing.
Don't get discouraged when you're close. Think about all the things that
you got right, not the one thing that is giving you a hard time :)
Bruce
11322 Fri, 3 Mar 2000 13:06:19 -0500 (EST) [alt-beam] No Subject beam@sgiblab.sgi.com Allan Graves I'm looking at building a walker, a 3 motor, using the schematic found on
http://www.geocities.com/SouthBeach/6897/walk3.html
(Chiu's site).
I've been trying to find info regarding the best motors to use, and when I
looked at solarbotics page, they had more than a few makes. I've looked
in the faq, and really don't know: Which motors should I use for
this? The pager motors look too small, and the others look too
big. Help? Thanx.
--
Allan Graves
"Remember, only trained ants with backpacks, gravity, and E-fields can
make a charge move..."
Bob Davis
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