Subject:
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Re: Mini-RCX
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 25 Oct 2004 23:38:10 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.net*antispam*>
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Viewed:
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918 times
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T. Alexander Popiel wrote:
> In message: <I63uB4.1yqM@lugnet.com>
> "Andrew G. Meyer" <agmlego@yahoo.com> writes:
>
> > Hi,
> > My brother and I have been tossing the idea around of a mini-RCX. We have
> > narrowed our idea down to a two sensor, two motor brick that would be
> > approximately 4X6 studs on top, and about two bricks high. We were just
> > wondering if anyone out there thinks something like this would even be
> > possible.
>
>
> Oh, it's possible (if you put the batteries someplace else)...
> there's more smarts than an RCX in a high-end wristwatch, and
> that's a smaller footprint than you specify. The trick is that
> to do it, you'd have to build it from the chips up, probably
> with surface mount and custom chips. All in all, it would be
> extremely expensive...
I don't see a problem with the computer side of things - what concerns
me is battery storage and power management. You can get *tiny* computers
that would easily fit in this kind of tiny space - but the RCX motors
need 9 volts - you would need 6 AA's or AAA's - but that won't fit in
a case that small. You'd have to go with a single 9v battery.
We know that the Lego battery box (which has a single 9v battery) is
4x8 studs and more than two bricks high...and all it has inside is the
battery.
So unless you are talking external batteries, I don't think it's possible.
If you are going with external batteries then the next issue is the power
circuits - those are quite big. You can't just wire a LEGO motor to the
outputs of the computer!
Here are photo's of the inside of the RCX:
http://graphics.stanford.edu/~kekoa/rcx/#Hardware
The big computer chip can undoubtedly be shrunk considerably - but all
of those surface mount resistors, power transistors, capacitors, etc
are all going to be needed and the technology for those things hasn't
changed in the slightest for at least 15 years.
The RCX's computer is only a tiny fraction of the volume of the RCX
box - you could shrink that onto the head of a pin and the size of
the overall RCX would hardly change at all!
So, I think the RCX could be shrunk a bit by removing stuff like the
LCD panel - but it's not going to get a whole lot smaller.
What you certainly COULD do would be to put a LOT more features
into the RCX by putting in a faster computer with a ton of memory
and lots more I/O - probably you'd want to add a radio interface
and faster networking...but the result would be about the same
size as the present RCX.
What I think would be a smarter idea would be to try for an idea
I've been suggesting for a couple of years now - to MODULARISE the
system. Take the power out into a separate battery box. Put the
computer into a box with no motor/sensor connections at all (it
would comfortably fit into a 2x4 brick) - but instead provide a
simple bus interface (something like I2C) with small, simple
computers in every motor and sensor that would communicate with
the main computer to do their work.
This would distribute the bulk of the RCX out amongst the sensors
and motors and permit much more flexible placement of batteries,
computer parts, display, networking components, etc.
---------------------------- 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 has 2 Replies:
 | | Re: Mini-RCX
|
| (...) Any idea on how I2C compares to 1-wire? I know that there 1-wire is being considered for some open-source home automation schemes because of the extremely low cost of interfacing, and the data rates seem comparable 115k for 1-wire vs. 100k for (...) (20 years ago, 26-Oct-04, to lugnet.robotics)
| | | 1Wire vs I2C
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| (...) I2C is much faster (100 Kbit I2C is the slowest, vs 14 Kbit 1Wire), more reliable, but much shorter distance. Newer I2C can be 1 Mbit or more. (...) 1Wire will never do 115 kbits reliably. The 1Wire overdrive option is not reliable and few (...) (20 years ago, 26-Oct-04, to lugnet.robotics)
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Message is in Reply To:
| | Re: Mini-RCX
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| (...) Oh, it's possible (if you put the batteries someplace else)... there's more smarts than an RCX in a high-end wristwatch, and that's a smaller footprint than you specify. The trick is that to do it, you'd have to build it from the chips up, (...) (20 years ago, 25-Oct-04, to lugnet.robotics)
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