Subject:
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Re: interfacing PCs with LEGO?
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 20 Aug 2004 16:41:01 GMT
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Original-From:
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Mr S <SZINN_THE1@YAHOO.nospamCOM>
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Viewed:
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1042 times
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Joe,
I have spent time building LEGO robots, and there are
a few things that you should know about LEGO while you
are doing preliminary planning in your thoughts.
Here is a link to comparison information about the
LEGO motors.
http://www.philohome.com/motors/motorcomp.htm
I don't think they are as powerful as you imagine.
What you have suggested would seem to require that at
least three of these motors be physically located in
the arm/wrist/hand areas, while the shoulder could
have them located in the body of your robot. LEGO is
plastic, and you will find ways to bend and break it
if you increase the force of any LEGO mechanism
enough. I've got a gearing system of 245-ish:1 and
that is enough to twist an axle into uselessness.
It is possible to build H-Bridge circuits to
power/control the LEGO motors, and you can interface
serially to your RCX programs using the IR port. The
question would then be ... why do that? By the time
you have spent money on LEGO parts, and external parts
to drive the LEGO, you might as well (from a cost
point of view) have started out with a different
controller, motors or servos, etc.
My robot is kind of heavy and large. Its managed to
roll around quite happy with 52 AA batteries on board.
I have an arm on it with 5 DOF including the gripper,
and had to use servos for 3 of those DOFs in order to
get the torque to weight ratio required. The shoulder
is all LEGO, the elbow, wrist, and gripper are
mini-servos controlled through the IR port to a servo
controller. Even though I managed to do this, it has
taken numerous rebuilds to strengthen various aspects
of the structure of the robot, including the wheels,
drive train, and other parts that simply failed under
the load of the size and weight of itself.
If you are planning on something large, LEGO might not
be where you want to start. It *IS* the place to start
if you want to learn about robotics, and many of the
tasks that autonomous robots must deal with.
Hope that helps
Cheers
--- Joe Strout <joe@strout.net> wrote:
> Disclaimer: I'm not into LEGO robotics yet, so I am
> quite likely full of
> baloney. I hope you'll humor me anyway.
>
> Preamble: I'm thinking ahead to when I might get
> into LEGO robotics, and the
> sorts of projects I'd like to do. I'm a software
> engineer with a background in
> vision and some experience in natural language
> processing, and I'd like to take
> advantage of those. But those require a "real"
> computer -- and the beefier, the
> better, as they're very processor-intensive.
>
> I'm also thinking of the number of degrees of
> freedom I might like to have in my
> robots (four for the hand, one for the elbow, two
> for the shoulder... and that's
> just one arm!), and dividing this by the number of
> outputs on the RCX. Then
> multiply by the cost (and bulk) of an RCX... ouch.
>
> Then I notice that you can buy a complete,
> plug-and-play Linux box at Walmart
> for $300, complete with a decent CPU, hard drive,
> power supply, etc. -- just add
> monitor, plug it in, and turn it on.
>
> All this has led me to ask...
>
> My Question: Can anyone point me to resources about
> interfacing an ordinary PC
> with the LEGO inputs and outputs? Instead of an
> RCX, I'd like to get the guts
> of a cheap PC, stick it in a largish LEGO robot, and
> have that control
> everything (and program this board by plugging in an
> ethernet cable and simply
> SSHing to it). Is this doable, without going
> through the RCX? What sort of
> interface hardware would I need?
>
> Thanks,
> - Joe
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Message is in Reply To:
 | | interfacing PCs with LEGO?
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| Disclaimer: I'm not into LEGO robotics yet, so I am quite likely full of baloney. I hope you'll humor me anyway. Preamble: I'm thinking ahead to when I might get into LEGO robotics, and the sorts of projects I'd like to do. I'm a software engineer (...) (20 years ago, 20-Aug-04, to lugnet.robotics)
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