Alt-BEAM Archive
Message #11325
To: beam@sgiblab.sgi.com
From: "Ben Hitchcock" beh01@uow.edu.au
Date: Sat, 04 Mar 2000 07:52:10 +1100
Subject: [alt-beam] Re: My walker ain't walkin'
Hi,
> "Simple contact switches to cut the
> delay are what you want with high gearing."
>
> are you saying putting the switches to cut the power feed of the motor, or
> into the core?
No, put them into the core.
What you need is a normally open switch with one side connected to ground,
and the other side connected to the input of the neuron that fires that
motor that way.
Hmmm not very well explained.
Righto, what the switch does is ground the input that is high at the time.
So you need to find the neuron that makes the back leg go left. Put the
switch in between the input of this neuron and ground, and physically put it
so that it trips when the leg is at its leftmost position. Repeat for the
right hand side.
As suggested, you can put a 10k or so resistor in series with this switch if
you feel like doing things properly, but then again if you were doing things
properly you wouldn't be using a chip to drive your motors.
Ben
11326 Fri, 3 Mar 2000 15:55:03 EST [alt-beam] Cricket circuit beam@sgiblab.sgi.com Gadagada@aol.com Hello all!
I remember a "cricket" circuit coming through the mail list a while back. It
had places where you could vary the pitch, duration of beeps, and beeps per
minute from a piezo buzzer. Does anyone still have that? If you could email
it to me privately, that would be great. It is quite urgent.
Thanks alot
Gary
11327 Fri, 03 Mar 2000 13:59:03 -0700 [alt-beam] Tuning (was: Current draw questions...) beam@sgiblab.sgi.com "John A. deVries II" At 08:35 AM 3/3/00 , Wilf wrote:
>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.
If you supply a motor with an insufficient amount of power, it doesn't turn
at all (but eats the energy), right? And it takes some minimum amount of
energy to get past the "threshold" -- that is, to get the motor to turn at
all, given a certain load. Even once you've gotten it past the "hump" the
power characteristics of a motor changes as it gets up to its "steady
state" rotation (presuming you have enough power to get to that
point.) Then, the motor will turn until you quit supplying power and even
then there will be -some- rotational inertia.
So... a similar question recently was posed: I believe it had to do with
getting the most out of a bicore-driven system. Basically, it seemed to
ask the question of frequency vs. pulse width ("big steps vs. little
steps", if you will). I believe that the setup that Wilf is describing
would go a long way towards determining what the best pulse width would be
when you are still breadboarding if the amount of energy available for your
'bot is severely limited (say, for example, if your motor power is derived
from an SE). You'd be looking for the greatest number of revolutions given
the smallest pulse (trying to maximize the ratio of
#revolutions:pulse-width in other words).
Z
11328 Fri, 3 Mar 2000 16:02:57 EST [alt-beam] Re: My walker ain't walkin' beam@sgiblab.sgi.com BUDSCOTT@aol.com on the almost complete walker circuit, which are the timing resistors? i'm
not very familiar with the workings of the bicore, but that might be a little
too rich for my blood, mybe i'll use rubber band bungees.
-Spencer
11330 Fri, 03 Mar 2000 15:10:31 -0600 [alt-beam] Re: My walker ain't walkin' beam@sgiblab.sgi.com Richard Piotter Like I said, attach the switch in series with a small resistor and then
take that and put it in parallel with the resistor that determines the
timing of the =B5Core or Bicore Nv that drives that particular motor. I
add the resistor so it's not a sudden drop of the process. It alsdo
gives the thing a little "chaos". Keep the resistor small enough, and
use long bars on the switches that will give a bit. Work with the timing
and you'll figure it out.
"Vermeulen, Vincent" wrote:
>=20
> "Simple contact switches to cut the
> delay are what you want with high gearing."
>=20
> are you saying putting the switches to cut the power feed of the motor,=
or
> into the core?
>=20
> -----Original Message-----
> From: Bruce Robinson [mailto:Bruce_Robinson@telus.net]
> Sent: Friday, March 03, 2000 0:16
> To: beam@sgiblab.sgi.com
> Subject: Re: My walker ain't walkin'
>=20
> BUDSCOTT@aol.com wrote:
> >
> > i just finished *whew* my first walker, ...
>=20
> > ... the motors occilate, but the bot looks as if its doin a @#$&in'
> > mating dance! What should i try ...
>=20
> 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 o=
f
> 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.
>=20
> > ... i'm gonna put motor stops so the ...
>=20
> Richard's right on about the stops. Simple contact switches to cut the
> delay are what you want with high gearing.
>=20
> Don't get discouraged when you're close. Think about all the things tha=
t
> you got right, not the one thing that is giving you a hard time :)
>=20
> Bruce
--=20
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!!!
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30
11331 Fri, 3 Mar 2000 15:25:27 -0800 [alt-beam] Re: My walker ain't walkin' "Phillip A. Ryals" >> but then again if you were doing things
>properly you wouldn't be using a chip to drive your motors.
>Ben
Be nice! :)
11332 Fri, 3 Mar 2000 17:46:34 -0500 (EST) [alt-beam] Re: Current draw questions... beam@sgiblab.sgi.com chipuser ------- Original Copy -------
SNIP
>Hi Wilf!
>
>Thanks fotr the input! The reason that I asked was that
the reading I was
>getting started out at one value and then dropped to a
lower value. It
>seemed to be pretty low, so naturally I thought that I
muffed it. :)
>
>The test was using a variable bench supply set as low as I
could get it. I
>hooked the 0V lead to the cap, the black lead of the meter
to the pos cap
>lead and the red probe to the +V of the supply. I then
turned the fine
>current adjustment up until the cap started charging. The
reading at that
>point was 20.31mA. After about a half minute it dropped
to
just over 15mA.
>The robot was operating the whole time that I was
recording
values, btw.
>
>Would this be representative of the overall system current
draw? I'd hate
>to tell folks that it operated at the wrong level!
>
>Thanks!
>
>Richard
Looks like you had the power supply in a current limiting
mode. In circuits like a solar engine there are 3 types of
readings you could get.
Overall system current draw is difficult to define.
reason(s)?
1)The motor takes a certain amount of current when supplied
with a fixed voltage. In a solar engine, the motor never
sees constant voltage. So this is one part of the reading.
You can measure the motor current by saperately feeding it
with a fixed voltage (may be equal to the solar cell
voltage) & loading it apropriately (use Wilf's method if you
want). If not, when you connect the meter in series with a
motor in a solar engine, you will see a high current reading
quickly die out - due to the discharge characteristic of the
capacitor.
2)When the capacitor starts charging (and till the engine
triggers to discharge it), if you connect a meter between
the cell & the circuit, you will see a current value that is
initially limited by the short circuit current value of the
solar cell (at that illumination). As the capacitor
charges, this value will start dropping. This is the second
reading I mentioned.
3)With the meter connected as above, When the capacitor is
nearly charged to the trigger point & the engine is yet to
trigger (this condition doesn't last long) you can get the
third reading which is roughly equal to the consumption of
the rest of the circuit including capacitor leakage etc. To
measure this value, use a power supply set to just below the
trigger point and connect the meter between supply and
circuit. Measure the current only after a long time
allowing the capacitor voltage to stabilize.
This last reading tells you the lowest current capacity you
must get from the solar cell in order for the solar engine
to fire once in a while (the while will depend on how much
current in excess of the this value you get)
Because of all the fluctuating current values you encounter,
it is useless to try to measure the overall system current
draw. To gauge the efficiency of the overall system, use
the methods suggested by Wilf. The only useful information
you can get otherwise is the 3rd reading I mention above.
Your reading of 20.31mA stayed there for you to read only
because the power supply was in a current limiting mode.
Hope this clarifies the problem you are facing.
ChipUser
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11333 Fri, 03 Mar 2000 15:01:07 -0800 [alt-beam] Re: photoresistors beam@sgiblab.sgi.com Bruce Robinson Sathe Dilip wrote:
>
> I think the standard symbol for a photo resistor is a simple resistor
> enclosed in a circle ...
Thanks. It's just become my standard :)
Bruce
11334 Fri, 3 Mar 2000 18:29:20 EST [alt-beam] Re: 4+ motor walkers beam@sgiblab.sgi.com Bumper314@aol.com In a message dated 3/3/00 7:43:54 AM Mountain Standard Time,
sparkyg@seark.net writes:
> ????
If you have aol IM or ICQ I can talk to you tonight, right me back
Steve
11335 Fri, 03 Mar 2000 18:21:14 -0600 [alt-beam] The Richfiles web page is back online! BEAM , Twin Cities Robotics Group Richard Piotter Hello! My page is back online. FOr now, you must use the following
address. My old address isn't yet reactivated. Very shortly, I should
have a few videos online. In order to keep space down, I may cycle
through videos every now and then, untill I either have a remote space
to run the videos, or if I recieve an OK to use more. I'll probably
temorarily drop the Algo's FACTory videos in favor of the robotics
videos. I'll have to just see how things turn out.
An update should occur soon. Hopefuly the new videos will go up.
http://www.calc.org/hosted/richfiles/
--
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
11336 Fri, 3 Mar 2000 20:33:17 EST [alt-beam] Hexitiles beam@sgiblab.sgi.com BUDSCOTT@aol.com I keep seeing and hearing about these hexitile deals. I know that they are a
kind of PCB, but what makes these tiles so special? the do look neat on
Tilden's turbots and photovores, but could somebody explain what signifigance
the shape is.
-Spencer
11337 Fri, 03 Mar 2000 21:54:17 -0400 [alt-beam] Re: Hexitiles alt-beam@egroups.com michael.hirtle@ns.sympatico.ca (Michael Hirtle) I don't like the shape my self but the shape is good because they can be conected
together better more efficiently that way, and the shape looks good to some
people too
BUDSCOTT@aol.com wrote:
could somebody explain what signifigance
the shape is.
> -Spencer
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