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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Sat, 21 Aug 2004 03:13:25 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.%ihatespam%net>
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Viewed:
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1115 times
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Joe Strout wrote:
> 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.
It's pretty challenging to build such a thing out of Lego. Having all of those
degrees of freedom down at the hand tends to push you to solutions where the
motors and sensors for those things are a long way out on the arm - that means
that there is a lot of weight where you are furthest from the shoulder joint.
This results in the need to build really chunky, solid structures - which in turn
leads to really slow gearing...more weight...more structure...more motors...
I'm not saying it's impossible to build such a thing - but it's not going to be
easy.
> 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.
Yep.
> 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?
Well, the simplest way is to have the computer talk to an RCX via the IR interface.
If the RCX is too expensive - you could trawl BrickBay for some used Scouts (*not*
microScouts) which are like little RCX's - less memory for programs, only two sensors
and only two motor outlets - but cheap - and still something you can talk to from
the PC.
> 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?
Talking to Mindstorms motors would require some power transistors or something.
There are some web sites out there with schematics of the RCX - you could copy
the relevent motor interface circuits relatively easily.
But would you really need Mindstorms motors? If you are crossing the line
beyond stock Lego parts then why not use radio control model servo-motors.
Those are powered on one wire and their position is determined by a simple
5 volt pulse-width modulated signal on a separate wire - with ground on the
third wire.
You can drive at least 8 of them from a standard PC parallel port without
*any* interface electronics. They also have on-board sensors so you tell
them where to move to - and they go there without further attention from
you. Getting Mindstorms motors to do that is a lot harder. You can also
get servo's in a wide range of sizes - ranging from *tiny* ultra-lightweight
(but not very powerful) motors that would be fine for moving the 'hand' -
through large chunky motors that the model yacht guys use for pulling sails
around that would be suitable for the shoulder and elbow joints.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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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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