Alt-BEAM Archive
Message #13666
To: beam@sgiblab.sgi.com
From: Lee Golden beam@sgiblab.sgi.com
Date: Wed, 19 Apr 2000 02:36:44 -0700 (PDT)
Subject: Re: LDR's in Bicoreeos Smart Head?
A word of caution about the part #PRE-14 LDRs from All
Electronics. I ordered ten of them and they all have
*greatly* different resistances in light and dark. In
fact, they even sent two different types when they
were all supposed to be the same. They are really
tiny, but when you are using them in pairs for a Solar
Head etc. you need to find two that are close in value
under the same lighting conditions.
Lee Golden
--- leif_ 74 wrote:
> >What are LDR's and where can I get them?
>
> They are Light Dependant Resistors, and you can get
> them at
> Allelectronics - 5K
>
http://www.allelectronics.com/cgilocal/SoftCart.exe/online-store/scstore/p-PRE-14.html?L+scstore+mkty1131ff996999+961905237
>
> Allelectronics - 500K
>
http://www.allelectronics.com/cgi-local/SoftCart.exe/online-store/scstore/p-PRE-15.html?L+scstore+mkty1131ff996999+961905237
>
>
>
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13667 Wed, 19 Apr 2000 03:14:03 -0700 (PDT) Re: LDR's in Bicoreeos Smart Head? beam@sgiblab.sgi.com Lee Golden I'm sorry! I meant the part #PRE-15's have greatly
differing values, not the PRE-14's. Sigh...
Lee Golden
--- Lee Golden wrote:
> A word of caution about the part #PRE-14 LDRs from
> All
> Electronics. I ordered ten of them and they all
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13668 Wed, 19 Apr 2000 07:33:26 EDT Re: Costings in Australia beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 4/18/00 10:38:09 PM Eastern Daylight Time,
kits@robotOz.com.au writes:
> What we can buy products for in reasonable quanties from suppliers like
> Solarbotics, Digikey etc
> Buy a product at $10 USD.
OK, I can see paying US dollars for Digikey products, they are a US business.
But, I don't get why you and the rest of us pay US dollars for Solarbotics
products. Are they not a Canadian business? I order from other Canadian
businesses and they charge at a Canadian rate. This gives us yanks a 40%
discount because of the exchange rate. That's the way it is supposed to work.
At present, US customers (and from what I can gather from your comments,
Australian customers as well) are being hit with a 40% penalty. Or does my
calculator work different from everyone else's?
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
13669 Wed, 19 Apr 2000 08:02:51 EDT Re: Costings in Australia beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 4/18/00 11:55:31 PM Eastern Daylight Time,
elmo@ilid.com.au writes:
> In the
> mean time, chin up, face east (or at least toward Canberra anyway) and
bare
> your
> buttocks in a true Aussie salute to the bizarre logic that is the
Australian
> political system. :)
I don't know a lot about the Australian tax system, but I do know this, The
country's that are charging higher tax rates and coming up with weird sources
of revenue, usually have decent humanitarian public services. Health care,
welfare, training incentives, etc. I know this is true in Canada. It's true
in Europe as well. Americans seem to view any tax as an infringement on their
wealth building schemes. So, we have the highest rates of homelessness,
almost no health care to speak of, and a welfare system that could be called
brutal. We (American's) are presently swamped by a conservative wave of
selfish me-ism. Our solution to homelessness is to make it illegal to be
homeless (go figure). So, don't knock a tax role that makes your country more
conscientious. Some American's are enjoying the fruits of the present system,
but, I think, at the cost of our nation's humanity.
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
13670 Wed, 19 Apr 2000 08:07:42 EDT Re: Costings in Australia beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 4/19/00 2:50:40 AM Eastern Daylight Time,
cactus@dynamite.com.au writes:
> Also, a lot of the stuff we buy from the US probably came from Asia
> originally. You could probably undersell North American suppliers by
> getting
> those things straight from the source.
Now you are cookin' with gas, baby!
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
13671 Wed, 19 Apr 2000 23:50:48 +1000 Dummy Walker beam "Ben Hitchcock" --MS_Mac_OE_3039033048_720959_MIME_Part
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Well,
I've finally ironed out the bugs (I hope!) in the "getting stuck" detector
on my walker. Now when the walker gets stuck it will wait for a second or
two before spinning that motor the other way and starting the gait again.
I tried putting a reversing circuit on it before I reached this solution.
This used up all the inverters, and was... interesting. When a motor
stalled, that motor would stop, and the other motor would swing over, it
would wait for a bit, then the first motor would turn. This had the effect
of slooowwwly 'backing up' forever. If you stalled a motor when backing up
the circuit wouldn't recover.
This isn't to say that reversers can't be done. I'm sure that someone can
come up with a better solution than mine - perhaps a touch switch that makes
the robot back up for a set time, or something. 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.
There are two circuits here:
dummy.gif:
This is my original dummy walker circuit. It is simply a walker circuit for
dummies. I couldn't get my microcore circuit to work reliably (Probably had
something to do with the modifications I did to it! I can't just leave a
circuit alone!) so I made this circuit instead. I could build this one
without any problems. This uses two servos, a 74HC14 and a 74HC245, a few
batteries and that's about it. It will walk reliably, except if a motor
stalls for some reason (Like walking on carpet). I regard this circuit as
doing pretty well for the response I get out compared to the number of
components.
The second circuit is nsdummy.gif. This stands for Not So Dummy walker. In
other words, it's a bit harder to put together. I don't think that this is
the optimum solution, but it's the best I could come up with. And it works!
I built the thing this afternoon, and it walks fine!
I have to say that I've been bitten by the walker bug now. I've got an
8-servo 4 legged walker half built sitting on my desk that I hope to control
with a CPU that was designed at wollongong university. I've got a black and
white analog camera that I'm going to mount on it as well. The leg design
is quite different to that of Richards quadrapod, although we will probably
be able to share control circuitry because the servos still do much the same
thing - forward, back, up, down.
Anyway I digress.
When building the dummy walker about the only thing that can go wrong is
that you get the motor polarity around the wrong way. This means that
instead of oscillating like any sane walker does, the motor drives to the
endstop and tries to keep going. Turning the power off and reversing the
leads on the motors fixes this. Murphy must have been looking over my
shoulder today because both my motors did this. What's that, a 25% chance
of happening?
You can have a look at a fuzzy picture I took about an hour ago at:
http://wollongong.apana.org.au/~ben/nsdummy.jpg
Although I put LDR's on the robot, and they change the center angle of the
front legs, I'm not convinced that the robot actually turns towards the
light. Has anyone gotten their walker to be light-seeking? If so, how do
you do it? Do you change the center position of the front or back legs? By
how much?
One more thing, when the circuit was breadboarded occasionally when I
stalled the front servo the rear one would go crazy, oscillating back and
forth and the front one wouldn't even move. I put this down to a high
reistance leak on that particular track because when the circuit was
freeformed the problem disappeared. Weird.
Anyway,
Questions, comments?
Ben
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13672 Thu, 20 Apr 2000 00:00:33 +1000 Re: Repost anyone? Photopopper questions from newbie. beam@sgiblab.sgi.com "Ben Hitchcock" Sorry about the lack of responses. I guess people were busy debating other
stuff (I'm guilty!!!)
Anyway, back to your questions:
>From: Ken Hill
> My problem is combining them into the beam-online circuits "Photopopper"
> circuit. I need to use LDRs but can't figure how to substitute them for
> the photodiodes exactly (read all the discussion but need pic:).
Just whack em in instead of the photodiodes. This will change the
characteristics of the SE, so will be either light avoiding or light
seeking, depending on how the LDR's are facing. Try it out! This may
increase the sensitivity of the trimpot making it harder to center the
popper. You may want to increase the 0.22 uF cap to a higher value to make
it easier to tune.
> Also, I'm not sure how the touch sensors work. Do they ground the V+ input
> to the 1381 keeping it from firing and letting the other motor turn it away
> from the obstacle?
Usually not. This is because if both sensors are tripped, your little bot
won't move at all :-(
I would put them in parallel with your LDR's.
> (Photopopper drawing shows the wires crossing near 1381s but not sure if
> they are connected at that junction).
>
> And lastly, is the RC timer (if that's what it is?) used to keep the motor
> from firing for a while assuring the turn or what?
Eh? RC networks? Where? The cap on the trigger of the 1381 is there to
allow different resistances of light sensor to have some effect... This is
an RC network I guess, but only if you replace the Photodiode with a LDR.
Is this what you're talking about? If so then yes the RC time constant is
affected by light, therefore the popper will be affected by light and will
either turn away or come towards the light.
> I can build em, but I want to understand em :) Thanks for any help.
>
> Ken
>
> P.S. It appears that if you are willing to use 2 solar cells (1 for each
> SE) that except for touch sensors, they really don't need to be combined
> and the cells can replace the photodiodes to change direction since if
> mounted angled away from each other they will catch more light on one side
> causing one motor to pop more often and turn toward the light. (Obvious you
> say - well I said newbie :)
Yep, some people have done this and it makes for an interesting bot. It
doesn't have nearly the same turning circle though.
hth,
Ben
13673 Wed, 19 Apr 2000 10:27:33 EDT Re: Dummy Walker beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 4/19/00 9:55:12 AM Eastern Daylight Time,
ben@wollongong.apana.org.au writes:
> I have to say that I've been bitten by the walker bug now. I've got an
> 8-servo 4 legged walker half built sitting on my desk that I hope to
control
> with a CPU that was designed at wollongong university. I've got a black
and
> white analog camera that I'm going to mount on it as well. The leg design
> is quite different to that of Richards quadrapod, although we will probably
> be able to share control circuitry because the servos still do much the
same
> thing - forward, back, up, down.
I'd love to see this thing when you get it finished. I'm contemplating multi
motors per leg now. It seems to me that at least three per leg is needed. I
think I may have come up with a way to get 3DOF out of two motors, but
haven't tested the idea yet (to many other projects ahead in the que). I
suspect at least 3DOF per leg is required for a nimble walker. I believe in
the simpler is better approach, but I also realize that walking creatures
ain't so simple.
> Has anyone gotten their walker to be light-seeking?
Well, yeah. Where have you been :)? Justin has built two that I know of. I
have built one to date. They work with a head (which can be static or moving)
to bias the pulses on one side or the other of both motors simultaneously.
This causes longer pulses on the "dark" side of the bot which, effectively,
turns it toward the light. The system works extremely well. But, I suspect,
that it works best if the head is immobile. The head on Ambler is great eye
candy, and works very well. But, I probably lost a small amount of
phototropic response and added unneeded parts to the jumble. Not to mention
added current draw. But, God, it looks good scanning for the light! If you
care to, check Justin's old site that has Ucoba and Sal. Also take a look at
Ambler on my walker pages.
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
13674 Wed, 19 Apr 2000 09:31:51 -0600 Re: Costings in Australia beam@sgiblab.sgi.com Dave Hrynkiw At 05:33 AM 4/19/2000 , JVernonM@aol.com wrote:
>OK, I can see paying US dollars for Digikey products, they are a US business.
>But, I don't get why you and the rest of us pay US dollars for Solarbotics
>products.
As I've said on previous occasions, over 90% of our business is conducted
in US Currency. Solarcells, capacitors, motors - these are the big-ticket
items that WE get charged for in US currency from companies in Canada,
Japan and (gasp!) even the USA. Funny eh? US Funds are the operating
capital of business world-wide. And since the large majority of our
customers are in the USA, it is just logical to make it our default currency.
As for Canadians getting a discount, that'll be changing soon. We simply
can't afford to process our orders at par anymore, so a new price list will
be online pretty soon.
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
13675 Wed, 19 Apr 2000 12:09:45 EDT Re: Costings in Australia beam@sgiblab.sgi.com JVernonM@aol.com In a message dated 4/19/00 11:38:55 AM Eastern Daylight Time,
dave@solarbotics.com writes:
> As I've said on previous occasions, over 90% of our business is conducted
> in US Currency. Solarcells, capacitors, motors - these are the big-ticket
> items that WE get charged for in US currency from companies in Canada,
> Japan and (gasp!) even the USA. Funny eh? US Funds are the operating
> capital of business world-wide. And since the large majority of our
> customers are in the USA, it is just logical to make it our default
currency.
Well, perhaps you should find the suppliers being used by other Canadian
suppliers and kit sellers. They seem to operate just fine by calculating in
Canadian funds. From what I could gather, Panasonic distributes in Canada,
but it is a less direct route to get them from US suppliers because demand is
to low to warrant stocking them in US companies. As a matter of fact, I
contacted a Canadian wholesaler about buying Panasonic products and they
refused to sell to me because they weren't allowed to distribute to the US.
If I understand what you are saying, Craig is selling his great stuff (sorry
Craig, you seem to be the easiest example) at quite a loss. I don't think
that's the case. He just rakes in less on the back end.
I don't want to go on with this, (but you still deserve a reply in the
interest of fair play) because it caused me not a little grief the last time
it came up. Let's just suffice to say that we agree to disagree. And please
people, don't tax Mr. Dalton's patience with dozens of "I love you Dave"
posts. I love him too. As a matter of fact, if I was a gay man... :). I love
my wife too, but I don't agree with everything she says or does (man, I hope
she doesn't read this :)).
See ya,
Jim
http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
ICQ# 55657870
13676 Wed, 19 Apr 2000 11:55:33 -0500 efficient launcher? beam@sgiblab.sgi.com "Phillip A. Ryals" I had this groovy idea, but I'm not sure if it can actually be done
efficiently. Maybe someone could give me some pointers?
I was thinking that it would be cool to implement a grappling hook type
system to allow a robot to get over large obstacles. It would require
some type of winch system that retracts the line, and I think this has
already been done with 'window washers'. But what about a launcher? I
really don't think there's an efficient way to do it with a solenoid or
motor... I just don't think a beam cicuit could really launch anything
very far. I think it would need to be a system where a gear motor
wiches the hook onto a spring. Then, you would need some sort of quick
release to get the full force of the spring. I think a big problem
might be the friction of the line used. That might be overcome if the
hook had some weight though.
Is this all just wishful thinking? It sounds like a LOT of trouble to
go to, but I think the effect would be pretty cool. Set the bot in
front of a wall three times it's height, and watch the bot climb it.
Any ideas?
-phillip
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