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RF modules with encoding?

T

Tony Williams

Jan 1, 1970
0
Spehro Pefhany said:
I'm looking for a small, and low power, pair of RF modules (send
and receive, only one-way communication) that could be used to
send a couple of messages (specifically, "ON" and "OFF" commands)
with encoding so that stray RF won't cause it to malfunction (the
consquences are expensive, and possibly even dangerous). Maybe
something in the ISM band. If the transmitter works off a key fob
with a button cell, all the better. It would be nice if there was
no local oscillator or other leakage of signals from the
receiver. There will probably be a number of receivers and a
single transmitter. Range is not an issue (a few dozen meters is
fine).

I used modules from <http://www.rfsolutions.co.uk> Speff.
From Farnell, or Newark in the US.
 
S

Spehro Pefhany

Jan 1, 1970
0
Hi, all:-

I'm looking for a small, and low power, pair of RF modules (send and
receive, only one-way communication) that could be used to send a
couple of messages (specifically, "ON" and "OFF" commands) with
encoding so that stray RF won't cause it to malfunction (the
consquences are expensive, and possibly even dangerous). Maybe
something in the ISM band. If the transmitter works off a key fob with
a button cell, all the better. It would be nice if there was no local
oscillator or other leakage of signals from the receiver. There will
probably be a number of receivers and a single transmitter. Range is
not an issue (a few dozen meters is fine).

It doesn't have to be really secure against deliberate attempts to
spoof the code, just against accidental actuation.

Any suggestions?


Best regards,
Spehro Pefhany
 
J

Joerg

Jan 1, 1970
0
Spehro said:
Hi, all:-

I'm looking for a small, and low power, pair of RF modules (send and
receive, only one-way communication) that could be used to send a
couple of messages (specifically, "ON" and "OFF" commands) with
encoding so that stray RF won't cause it to malfunction (the
consquences are expensive, and possibly even dangerous). Maybe
something in the ISM band. If the transmitter works off a key fob with
a button cell, all the better. It would be nice if there was no local
oscillator or other leakage of signals from the receiver. There will
probably be a number of receivers and a single transmitter. Range is
not an issue (a few dozen meters is fine).

It doesn't have to be really secure against deliberate attempts to
spoof the code, just against accidental actuation.

Any suggestions?

Check out the X-10 key fobs. Really cheap. Their receivers are IMHO not
very good so you'll have to roll your own.
 
G

Gary Tait

Jan 1, 1970
0
Hi, all:-

I'm looking for a small, and low power, pair of RF modules (send and
receive, only one-way communication) that could be used to send a
couple of messages (specifically, "ON" and "OFF" commands) with
encoding so that stray RF won't cause it to malfunction (the
consquences are expensive, and possibly even dangerous). Maybe
something in the ISM band. If the transmitter works off a key fob with
a button cell, all the better. It would be nice if there was no local
oscillator or other leakage of signals from the receiver. There will
probably be a number of receivers and a single transmitter. Range is
not an issue (a few dozen meters is fine).

It doesn't have to be really secure against deliberate attempts to
spoof the code, just against accidental actuation.

Any suggestions?


Best regards,
Spehro Pefhany

I have heard of some (like Holtek perhaps), although they do no more
than gate the carrier on and off based on the logic you feed them, and
present a signal at the receiver based on the status of that logic
signal entering the trasnmitter. Error correction and that would be don
by the logic you supply on either side. That said, you could use simple
remote control transmitter chips or a micro in the trasnmitter, and a
micro to decode, if no direct decoder IC is available..
 
G

GPG

Jan 1, 1970
0
I have heard of some (like Holtek perhaps), although they do no more
than gate the carrier on and off based on the logic you feed them, and
present a signal at the receiver based on the status of that logic
signal entering the trasnmitter. Error correction and that would be don
by the logic you supply on either side. That said, you could use simple
remote control transmitter chips or a micro in the trasnmitter, and a
micro to decode, if no direct decoder IC is available..

http://www.linxtechnologies.com/
 
T

Tesseract

Jan 1, 1970
0
I second the recommendation for Linx Technologies. You can get Holtek-encoded
keyfob transmitters with 1 to 5 buttons off the shelf and pair them with
their KH2 receiver/decoder modules for very cheap and Digi-Key stocks them.
Be aware, though, that Linx requires you purchase one of their evaluation
kits before they will sell to you direct anything not already FCC approved
(ie - you can buy the keyfobs but not the matching receivers without first
buying a stupid ev kit).

-Jeff
 
F

Fred Bloggs

Jan 1, 1970
0
... Range is
not an issue (a few dozen meters is fine).

Don't you have to stand back farther than that? Or is the operator
expendable...
 
S

speff

Jan 1, 1970
0
Don't you have to stand back farther than that? Or is the operator
expendable...

It's almost the reverse situation of what you are thinking...
 
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