From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2001-12-05 19:38:33
Jim,
> Can you help me with this?
> Please don't send me all over the place with links.
> I do not enjoy surfing as you seem to.
I'm showing you the source for the parts. I don't
know what your requirements are in terms of cost
or range or speed, and I don't know what kind of
signals you are sending
> Do you have any personal RF experience you are willing
> to share.
I have played around a lot with wireless ethernet
stuff like wavelan, proxim, and 802.11, plus other
packet-based stuff like ricochet and CDPD, but all
of these are for more sophisticated devices. I've
also played around with a few cheap transmitter
receiver pairs, in the ~400 Mhz range you mentioned.
> Can you write a few sentences giving your
> recommendations?
Most of the small RF stuff I have looked at are
really made for attachment to microcontrollers for
sending serial data streams. In this configuration
they are very easy to use since you already have
serial uarts on the microcontroller. This would
probably be the easiest way to implement it but
you need a microcontroller on body. So basically
do the amp/filter/digitize in a small module and
feed that into a transmitter via TTL serial. The
Atmel microcontrollers are small and cheap. You
should be able to make a much smaller module than
that 4x4 newmicros board. Then you can make a
small board with a receiver attached to a serial
port on a PC. Or, you can build some other kind
of remote device that does whatever you want.
These are the types I am familiar with. I'm not
very familiar with sending raw analog data over
RF and I would worry about noise. It seems to me
that it's better to digitize on body.
> What about performance and price?
Laipac low-end 433 Mhz modules are very cheap,
something like $10-$15. These operate at low
speeds, probably 9600 baud. Most of the cheap
RF modules max out around 9600 baud or less.
If you want more speed, you gots to pay. What
are your needs for speed and range? You also
have to pay attention to the FCC regulations.
You DON'T want to play around with modules that
are non free from requiring an FCC license.
> Could you "actually" build a prototype for me?
I'm sure I could. The actual wireless part is
pretty simple as described above. I say lets
try making your system smaller, and I will cook
the RF section for you. What do you want to send
to? And why? What happens on the remote end?
-- Doug
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