Subject:
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Re: advantages and disadvantages of IR vs. RF?
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 8 Dec 1998 03:31:46 GMT
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Viewed:
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1148 times
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In article <F3MB2J.Atn@lugnet.com>, "Anja McClellan"
<anja_mcclellan@broder.com> wrote:
> What are the strengths and weaknesses of using infra red rather than radio
> frequency?
Some general observations...
IR won't go through much mass - it is very similar to visible light in
this regard. RF is better at this - the waves are longer, so they can go
through things like 1/4" drywall.
It is easier to focus IR than RF. For this reason, it is relatively
simple to constrain IR to a small "cone", where RF usually propogates as a
sphere(1). This can be an advantage for IR (less battery power per bit of
transmitted information), or for RF (don't need to "aim" it).
At modest data rates (say 50kbps to 1MBit) IR hardware is significantly
cheaper than RF hardware. Part of this is certainly due to the large
volume of IrDA hardware, whereas there are few mass market RF applications
at these data rates. At lower data rates, the price difference isn't as
severe. Recent developments in wireless local area networking may close
this price gap in the near future.
RF spectrum must be allocated from national agencies (the FCC in the US).
Certain bands are set aside for "unlicensed" use, but in many cases this
can be a regulatory nightmare as the same frequencies are not always
available in every country. It also adds additional steps in getting a
product "certified". I know of one product that was originally intended
as an RF product, but was switched to use IR strictly because of
complications associated with getting the RF licensed in Germany. To my
knowledge, IR doesn't fall under this sort of regulation.
It can be a lot easier to build an IR interface than an RF interface. RF
design has a lot of pitfalls, and experts are difficult to come by. IR
design is fairly "cookbook" for most applications. Basic knowledge of
analog design is sufficient - you don't have to worry about antenna
design, etc. Test equipment for IR is a lot cheaper than RF test
equipment, etc.
> Why does Cybermaster use RF and Mindstorms IR?
Pure supposition....
Since Cybermaster is intended to be used as a "remote control" system, IR
wouldn't work very well (you'd have to keep aiming it, etc). RF is the
only effective choice here.
Mindstorms was designed as more of a point-to-point communication system.
Put the robot next to the computer, download your program, then set the
robot loose. Since IR is cheaper/easier, it was used instead of RF.
Dave
(1) Huge simplification. RF propogation is a nasty thing to compute.
--
reply to: dbaum at enteract dot com
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Message has 1 Reply:
 | | Re: advantages and disadvantages of IR vs. RF?
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| (...) Also, Cybermaster was targeted to be used as an interactive game, with kids crawling around the bot while it communicates with the pc. Hence the need for RF instead of IR. Eric Brok Visit LEGO ON MY MIND: (URL) Control section: (URL) section: (...) (26 years ago, 8-Dec-98, to lugnet.robotics)
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