Subject:
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Re: A Generic Idea
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 5 Jan 2003 06:37:21 GMT
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Original-From:
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Steve Baker <sjbaker1@ANTISPAMairmail.net>
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Viewed:
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977 times
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Xyvind Steinnes wrote:
> Ok, if radio built into the RCX is out of the question, what about the
> RC-modells? They have a Radio link? One way only, but that could be changed
> by using two transmitters and two receivers...
The problem is that the 27MHz frequencies are fairly tightly restricted
in some countries. Here in the US, it's pretty much open-season, it's
used by CB radios, radio controlled models - and various toys.
However, in other countries (the UK for example), it's illegal to use
27MHz to data transmissions - and the waveband is split into (IIRC) twelve
narrower bands to allow a dozen RC models to be controlled at the same time.
Add in the other dozen countries where Lego sells - and it becomes a
potential mine-field.
For a simple radio controlled car ("model"), they can use 27Mhz fairly
freely - however, sending computer data over it and using it bi-directionally
would be illegal in the UK. (for example).
Aside from 27Hz, you are in even deeper trouble. The only other toy/model
waveband in the USA is 49MHz - but that's illegal in the UK. In the UK, there
is also 35MHz - but that's only permitted for FLYING models (in an attempt to
improve safety and keep the toys away from the serious enthusiasts) and all new
transmitter designs have to be certified by some government authority at enormous
cost. In other parts of Europe there is a 56MHz band - but that's illegal in
both US and UK.
Multiply this problem by all the countries that Lego sells to and you can
just imagine the problems they'd have. It's VERY difficult to produce a
mass-market product that can sell around the world and jump through all
the legal hoops.
Cheap 27MHz toys are RELATIVELY unregulated...so long as they are simple
RC toys. A computer link though 27MHz would be illegal in lots of countries
even if it was using the exact same protocols in the exact same way.
I have some personal experience with this from the mid 1980's.
Many years ago, I designed a flight simulator program for radio controlled
aircraft. It used your standard RC transmitter and reciever and the program
came with a little box that plugged into the reciever like it was a set of
servo-motors - and sent that data to your PC along the serial port. The software
used the servo position data to control a flight model for the simulated plane
which was then displayed in 3D on the screen.
My father (who owned an RC model shop at the time) wanted to market it and
made enquiries. It turned out that controlling a SIMULATED model aircraft
constitutes COMPUTER DATA TRAFFIC - and is illegal on the 27MHz band in the
US and UK...even though the radio transmitter would have been a standard model
aircraft unit.
As it turns out, we weren't actually breaking the law by selling the interface
box or the software - it would only be the end user who broke the law. So we
just printed a disclaimer that said that you'd have to license the unit with
the FCC (which everyone ignored) and marketted it regardless.
> You can use that frequency to transmitt some codes, even if the bandwith is
> low?
> Probably to low for an color hig res picture, but what about a lowres b/w
> picture. And only with low framerate?
No - you still don't have enough bandwidth. The whole 27MHz band is about
1MHz wide - but that doesn't mean that you can send a megabit per second
through it. Radio controlled model transmitters send up to about eight
analog signals sampled at just 50Hz...that's maybe equivelent to 400 bytes
per second (not as good as that really - but we'll be generous.)
Even an ultra-crappy 320x160 monochrome image consumes over 50,000 bytes of
data and would take two *MINUTES* to send using a 'conventional' 27MHz radio
channel. That's unlikely to be acceptable in any application I could imagine!
You could do some data compression on that - and reduce the bits-per-pixel,
but you'll never get down to anything remotely reasonable.
You could design a radio that worked at 27MHz that sent the image much
faster than that - but radio is funny stuff - you get all sorts of weird
out-of-band signals that would interfere with god-knows-what else...that
would certainly be illegal in pretty much any country in the world.
> > > 3) The same would of course be true for the phone types which have the
> > > ability to take, send and receive pictures.
>
>
> Here in Norway they probably will try out the new type of mobile
> comunication this year (UMTS I think it was). It is were you in the future
> (when the mobile telephone company can make one...) can send live video
> streams with sound trough the air using only a small phone on the size of an
> big GSM phone today. They have been testing it for one or two years now, and
> the first radio-link towers are activated now for use in Rescue Helicopters,
> were the doctors have one camera like this and can send a live video feed to
> the hospital. With even more equipment attached to this he can also sends
> some other vital data from the site, like heart rate and so on.
Yes - phones with onboard video cameras are becoming possible in many places
around the world. This is interesting stuff. Dunno what frame rate they
use - but they are almost certainly using adaptive compression techniques
that only transmit the parts of the image that changed. That may produce
exceptionally poor images from a robot that's driving around because it's
likely that all of the image will change every frame.
Still - it's certainly happening.
The nasty problem is still that you have no way to get the image out
of the recieving phone and into a computer or something...that's OK for
"spy camera" type applications - but hopeless for the interesting stuff
like robot navigation, robot vision, etc, etc.
If all you want is a radio-linked spy cam - then go to www.thinkgeek.com
and check out their 'Desktop RC Mini-Rovers'. These are available here:
http://www.thinkgeek.com/cubegoodies/toys/59eb/
...with a tiny video camera that broadcasts a colour image to any
UHF Television that happens to be in range.
It costs $130 and has a range of 100 feet with a battery life of 3 hours.
I suppose you could buy an NTSC TV tuner/video-grabber card for your PC
and grab the image that way.
I'm told that the quality is pretty awful - and that you need really good
lighting to see anything much...but that's hearsay - I havn't seen one of
these myself.
> So all we can conlude with todays equipment is that you need more CPU power
> to handle the data from a camera?
For applications other than "spy camera", I think you need to take a
conventional 'webcam' camera like the vision command device - but have
a computer ON THE ROBOT analyse the image and decide how to act on it.
The RCX really isn't fast enough to do that - and the amount of electronics
needed to interface it to the camera is probably comparable to the amount
you'd need to add a second microprocessor to analyse the images at reasonable
speed.
> Can a palm do this? Or other smallsize computers that exist today?
Yes - a modern Palm could probably do a good job of it. Maybe you could
interface a USB Webcam to it?
> Does anyone know of such a device?
> My thinking was to use a usb camera and the usb tower connected to this
> "robot brain" to controll the RCX from inside the same robot.
> And some of these palm-size computers probably have built in (or can be
> connected to) GSM, so there should be no problem sending the result of an
> spy mission back to base and sending back information about what to do next.
> Was that a stupid idea?
Depends on the bandwidth that the GSM provides for digital data - and on
how much the Palm allows you to get at from within a normal user application.
---------------------------- 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 1 Reply:
 | | Re: A Generic Idea
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| (...) Well, to find outline of objects you'd need a low-res (easy to simplify and automatically filters out irrelevant details), color (to avoid two objects of the same material getting their outlines fused together by the image processing (...) (22 years ago, 5-Jan-03, to lugnet.robotics)
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Message is in Reply To:
| | Re: A Generic Idea
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| "Steve Baker" <lego-robotics@crynwr.com> wrote in message news:3E171F4A.400050...ail.net... (...) :) (...) inventions (...) I'm (...) IR-connected (...) enough (...) would (...) processing. (...) legally (...) country. (...) at (...) Ok, if radio (...) (22 years ago, 5-Jan-03, to lugnet.robotics)
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