Alt-BEAM Archive
Message #11500
To: beam@sgiblab.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Tue, 07 Mar 2000 21:45:46 -0600
Subject: [alt-beam] Re: MicroCore vs. BiCore
Well of course you won't get decent feedback through a buffer or driver
of any kind. Many of Tilden's bots use VERY efficient motors (like
escaps), and sometimes minimal driver circuitry. There are, from what I
understand, two forms of motor/Nv feedback are currently
recognized/debated/rejected, depending on who you talk to. Supposedly,
depending on how little isolation you achieve between motor and Nv, you
can supposedly effect the charge time of the capacitor based on motor
current draw. The Motor will draw more current under load. on high
efficiency systems with closely tied motors and Nvs, I presume the motor
will draww current, changing the time it takes to charge the input
coupling capacitor of the next Nv (longer, I presume). How does this
effect the circuit??? I'm not sure. The other suggested form of feed
back occurs when the load, even through a driver drops the total system
power. This would presumably effect the charge time of the whole circuit.
Now, the more efficient motors you have, and less isolation in the
drivers, the better your feedback will be. Also, if your motors have a
high enough current draw, they can saturate a microcore when they stall.
That alone proves that the motors can in one way or another have na
effect on the controler. That just so happens to be undesirable
feedback. Remember, motors can act like generators too. Even as they
turn, they create a reverse EMF (electromagnetic field). This increases
current draw.
You may not have sensors, but then again, the motors themselves become
sensors, indicating their own load.
BUDSCOTT@aol.com wrote:
>
> I'm gonna have to hook my bot up to a o-scope, and take a look at that. I
> cannot let myself think that either answer is wrong, but that is not only
> very improbable, it definitly borders impossible, i cant give a good answer
> for why it might do that, no sensors! If you look at what we're using, an
> octal bus IC, it can't really get good feedback from motors, that is too
> weird, has anybody else experienced this strange phenomenon?
>
> -Spencer
--
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
11501 Tue, 07 Mar 2000 22:45:01 -0700 [alt-beam] Re: old SE beam@sgiblab.sgi.com Dave Hrynkiw At 08:30 PM 3/7/00 , Bumper314@aol.com wrote:
>ok, just so you all know, this is where I am getting this idea from. attached
>is a picture of the robot, and what I think the schem is.
The LEDs on this SE-based Magbot Solaroller are wired up in PARALLEL with
the coil, but reverse-biased. When you de-energize a coil, it produces a
reverse spike of power, and in this case, it goes through the LED and
produces a quick blink, as well as protects the rest of the circuit from
the back-EMF pulse. Two, two, two applications in one!
-Dave
ps: That was still a bit of a large d/l. In the future, just put a pointer
to where the pic is on the web (ie: our website), and tag your file along.
---------------------------------------------------------------
"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
11502 Tue, 07 Mar 2000 22:24:56 -0800 [alt-beam] Re: MicroCore vs. BiCore beam@sgiblab.sgi.com Bruce Robinson BUDSCOTT@aol.com wrote:
>
> i know that i don't know a whole lot about the bicore, but i know
> enough about it to say that it is impossible for it to adjust to
> motor feedback, i also would say that it would be a suprise to me
> if the microcore had feedback as well. It is simply an electronic
> impossibility.
It's been debated many times. I once took the position that was a
mechanical phenomenon, not an electrical one. However, I was convinced
otherwise.
Briefly,
- your motor gets stalled.
- it draws more current, pulling down the voltage level
of the entire robot.
- this lowers the trigger threshold of your Nv inverters.
- the Nv delay changes.
This argument is sound, but it there are a few conditions that have to
be met.
- efficient motors with efficient gearboxes. Otherwise the
motor won't stall.
- shared motor & circuit supply, with relatively small wires
feeding the motors.
- the motor has to stall about the middle of the Nv delay period.
- there is a relatively short "window" in each cycle where the
effect is noticeable.
People (including me) have also noticed that increased motor noise (the
electronic kind) can introduce random signals to a microcore.
Definitely not impossible, but probably not as common as people believe.
Bruce
11503 Tue, 07 Mar 2000 22:24:45 -0800 [alt-beam] Re: MicroCore vs. BiCore beam@sgiblab.sgi.com Bruce Robinson Wilf Rigter wrote:
>
> If damn PNCs are you only concern, you can add 2 diodes to any
> microcore to make it PNCless.
>
> <>
>> -----Original Message-----
>> From: David Perry [SMTP:davidperry@geocities.com]
>> Sent: Monday, March 06, 2000 9:01 PM
>> To: beam@sgiblab.sgi.com
>> Subject: Re: MicroCore vs. BiCore
>>
>> my favourite reason for the bicore is you don't need no damn PNC!
And if you have something more complicated that the microcore, I've got
a nice little 2-inverter circuit that lets you put one or more startup
signals exactly where you want them (and nowhere else). Wilf's is more
elegant, mine handles a greater variety of networks.
Bruce
11504 Tue, 07 Mar 2000 22:24:41 -0800 [alt-beam] Re: Turning the walker beam@sgiblab.sgi.com Bruce Robinson BUDSCOTT@aol.com wrote:
>
> .... can you make a two motor walker turn, ...
Yep.
> ... if so, can you make it phototrophic? ...
Yep.
Bruce
11505 Tue, 07 Mar 2000 22:24:36 -0800 [alt-beam] Re: Was lobster, now bees beam@sgiblab.sgi.com Bruce Robinson Verne & Catherine Rambaud wrote:
>
> ... using sound would have problems too
> 1. they would have to develope a language that alone would
> take FOREVER ...
The builders have to provide the language, of course. This is not as
difficult as it sounds, for primitive communication.
The HPV sound circuit is capable of filtering out motor noise and other
ambient noise, so the robots tend to hear only themselves (more or
less).
The original sound circuit was designed to count "chirps" received. So
you can modify the circuit to send 4 or 5 different signals by having it
produce different numbers of chirps. And you can modify it to receive
those signals by counting the chirps.
Richard's original idea was to have two "ears" (tiny microphones) and
turn the robot according to which ear received the more intense signal.
How big a vocabulary do you want? At the present level of photovore
capability, the robot would "know" that it was in a poor light region, a
so-so light region, or a really great light region. That's about it.
Achievable with the present level of knowledge (but you're going to have
to do some of the development).
Bruce
11506 Tue, 07 Mar 2000 22:23:49 -0800 [alt-beam] Re: photoresistor head to BRUCE and OTHERS... beam@sgiblab.sgi.com Bruce Robinson William Cox wrote:
>
> Could you explain to me how I can make a slow oscillator?
The one I use for experimenting is a simple unbalanced bicore, made with
74HC14 Schmitt inverters. I use one Nv to adjust the frequency of pulses
and the other to produce a very short impulse which I feed to the two
Nv's in the head circuit.
The slow Nv has a 0.47 uf cap, and resistors vary from 2 meg on down to
100 k. The fast Nv uses a 0.01 uf cap and (right now at least) has a 1
meg resistor.
> Also, are the inverters in the schematic Schmidt?
Yep. That's what the funny little symbol inside them means (represents
hysteresis).
> Wouldn't I do the head and oscillator with a 74xxx14?
Yes. That's what I do.
> Do I have to use a H-Bridge? Or can I just hook the motor up?
Depends on the motor. The typical HC chip (e.g., 74HC14) is good for 15
to 20 mA.
If you need more current handling, you might want to use a 74HC245 or
'240 to drive the motor.
If you're going to use an H-bridge, try one of Wilf's "smokeless"
bridges.
If you're going to use a Tilden-style 6-transistor bridge (as shown on
BEAM-onine) you MUST use a 74HC139 decoder between the head circuit and
the bridge.
Bruce
11507 Tue, 07 Mar 2000 23:06:46 PST [alt-beam] Re: Tower hobbies servo beam@sgiblab.sgi.com "Timothy Flytch" Be vary careful with Tower... they are a lot like Rat Shak... They will put
their name on anything!!! They always use the lowest bidder... and are very
inconsistent... I would say stick to the name brands...
Timothy...
>i really want to start on a second walker and was thinking of using the
>servos from solarbotics (the tower hobby ones). Are they decent to use for
>the cost?
>
> -Spencer
______________________________________________________
11508 Wed, 08 Mar 2000 00:48:27 -0700 [alt-beam] Re: Tower hobbies servo beam@sgiblab.sgi.com Dave Hrynkiw At 12:06 AM 3/8/00 , Timothy Flytch wrote:
>Be vary careful with Tower... they are a lot like Rat Shak... They will
>put their name on anything!!! They always use the lowest bidder... and are
>very inconsistent... I would say stick to the name brands...
>
>>i really want to start on a second walker and was thinking of using the
>>servos from solarbotics (the tower hobby ones). Are they decent to use for
>>the cost?
We've never had any problems with these TS-53's - solid units, although a
bit noisy. But they're easier to modify than the HITEC units, which is a plus!
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
11509 Wed, 08 Mar 2000 03:08:59 -0600 [alt-beam] Re: Tower hobbies servo beam@sgiblab.sgi.com Richard Piotter How are Futaba brand servo motors??? Had one, but it was destroyed due
to mistakes by me! :)
The other Futaba I had was easily modified for continuous rotation.
I'm looking for a combo of durability, strenth (even if slow), and
efficiency. I want to make sure these things are worth the cost.
Dave Hrynkiw wrote:
>
> At 12:06 AM 3/8/00 , Timothy Flytch wrote:
> >Be vary careful with Tower... they are a lot like Rat Shak... They will
> >put their name on anything!!! They always use the lowest bidder... and are
> >very inconsistent... I would say stick to the name brands...
> >
> >>i really want to start on a second walker and was thinking of using the
> >>servos from solarbotics (the tower hobby ones). Are they decent to use for
> >>the cost?
>
> We've never had any problems with these TS-53's - solid units, although a
> bit noisy. But they're easier to modify than the HITEC units, which is a plus!
>
> 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
--
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
11510 Wed, 08 Mar 2000 02:44:38 -0700 [alt-beam] Re: Tower hobbies servo beam@sgiblab.sgi.com Dave Hrynkiw At 02:08 AM 3/8/00 , Richard Piotter wrote:
>How are Futaba brand servo motors??? Had one, but it was destroyed due
>to mistakes by me! :)
>
>The other Futaba I had was easily modified for continuous rotation.
>
>I'm looking for a combo of durability, strenth (even if slow), and
>efficiency. I want to make sure these things are worth the cost.
Very solid, proven, hobby industry standard units. Can't go wrong with
them. Can always find replacement parts for them
(gears/connectors/bearings/etc).
-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
11511 Wed, 08 Mar 2000 22:06:52 +1100 [alt-beam] Re: IR detectors beam@sgiblab.sgi.com "Ben Hitchcock" Hi,
> I bought a infared LED and infared photo transistor for radio shack for a IR
> detector and wired them up according to a circuit that I got out of some
> robotics book but it doesn't work. Either my components are bad or the
> circuit is. If anyone has made one of these before and could help me out I
> would appreciate it.
First of all, get your PT working. Grab a 1k resistor, and put it in series
with your PT, and attach a 5V supply to the whole thing. Now measure the
voltage on the 1K resistor while you zap it with a TV remote control. The
voltage should change. Keep fiddling with the connections until you get
this part working - swap around the leads on the PT until the 1K resistor
gets an AC voltage across it when zapped with the remote control.
Now get the IR LED, and find out which direction current will flow through
it by using the diode check function on your multimeter. Connect up a 470
Ohm resistor in series with the LED and attach the lot to a 5V supply so
that current flows through it the same way. Point the LED at the detector,
and Bob's your aunty's live-in boyfriend!
Ben
11512 Wed, 08 Mar 2000 06:35:20 -0500 [alt-beam] Re: Capacitor Values beam@sgiblab.sgi.com John Bachman Close, but not quite correct. The relationship is Xc=1/{2(pi)fC where Xc is the capacitive reactance at frequency f.
Coupling capacitors should represent an insignificant amount of reactance so they will pass the desired signal unimpeded. A factor of 10:1 is commonly used. So you must determine the source impedance at the coupling point and then calculate the minimum value of C that results in a reactance of 1/10 of that impedance. Any capacitor value exceeding that minimum should do nicely.
Good luck.
John
At 07:58 PM 3/7/00 , you wrote:
>Using the formula:
>
>1/{2(pi)FC} where 'F' is the Frequency and 'C' is the capacitance
>
>you'll get the capacative reactance, basically telling you what the
>resistance of the capacator is to AC...(since a cap in series blocks all DC
>you don't worry about the resistance to DC)...so if you were isolating the
>wave generator running at 1Mhz you would put that into the formula to try to
>find the capacator that would give you the least amount of reistance.
>
>example
>(rearranging the formula)
>C = 1/{2(pi)F}
>C = 1/(6.283 * 1^6)
>C = 1/(6.28^6)
>C = 159nF
>so for the smallest resistance you would want to throw a cap with as close to
>that value as possible...which would be 159nF...
>just hope this helps a little, let me know how it works out.
>Dan
>
><< The thought just occured to me, how do you pick values
> for capacitors when they're not part of a timing
> circuit? For instance, in school we're learning about
> amplifiers. Very simple, except for the two
> capacitors. I get why they're in there. I know what
> they do when they're not in there. But how do you
> derive the values? One blocks the DC from getting into
> the generator, effectively isolating it from the
> circuit. The other is tied between the emitter and
> ground, so that the AC we are generating doesn't turn
> off the transistor. Again, these are used to block DC
> and pass AC only. How do you go about getting the
> correct values needed?
>
> ~Daniel >>
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