Convert IR remote to RF remote

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I was wondering would it be easy, hard or near impossible to convert an
Infra-red remote control for a car stereo to work on Radio frequency
instead of IR?  I have seen a RF data transmitter/reciever pair in Dick
Smith or Altronics catalogue (can't remember which one).  Would it be as
simple as replacing the IR LED in the circuit with the transmitter
portion of the RF transmitter/reciever and replace the phototransistor
in the deck with the reciever portion of the RF transmitter/reciever?
Or will I have to make an IR reciever to attach to the RF transmitter
and then a IR LED driven by the RF reciever, like an IR remote extender?
  I would like to do away with the IR altogether.  I will worry about
how to hide the reciever and make the transmitter at least look
acceptable later.
Any advice appreciated

Matthew


Re: Convert IR remote to RF remote



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Try something like http://www.computronics.com.au/module/txrxpair /




Re: Convert IR remote to RF remote


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Cool.  This looks just like the one I had seen except smaller and
cheaper (less range 20m instead of 30m but that won't be a problem).
The best thing, computronics isn't far from where I live, but I didn't
even know it existed.  I will have to go there tommorow and see what
other cool stuff they have.
So let me see if I have this correct.  I should be able to connect the
Code input pin of the transmitter to the IR LED in the remote and
connect the Digital Output pin of the reciever to the phototransistor in
the deck and I'm done? Obviously connecting power and ground too.
Should I leave the IR LED in the circuit or remove it?  Same with the
phototransistor?  What should I use for the antenna? Just a piece of
wire 30-35cm long?  Is 3kb/s fast enough?

Cheers

Matthew


Re: Convert IR remote to RF remote



"Matthew Gunn"
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 **  Doubt it is quite as easy as that.

 IR  remote transmitters modulate the light beam at around 40 kHz   -  ie
the control code is actually sent as bursts of 40 kHz pulses, not just
simple LED on and off pulses.  So you will need to pass the LED drive
voltage through a low pass filter prior to the Tx unit to remove the 40 kHz
part.

Also,  an IR receiver's photo detector is tuned to respond to the same  40
kHz frequency only  -   so recovered data pulses from a radio Rx will have
to be fed in just after the IR units input stage.

You will need a CRO to have a hope of sorting this all out.




............   Phil



Re: Convert IR remote to RF remote


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What about if the data rate were faster, say 120kb/s or higher?  I don't
think such a thing exists but I will look if it is viable.  I don't
really want to mess around too much inside the deck itself, but i was
thinking if the data rate was fast enough, the RF signal could replace
the IR signal directly.  Does this sound right?

Matthew


Re: Convert IR remote to RF remote



"Matthew Gunn"
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**  Find a Tx/Rx combo that can handle a 50 kb/d data rate and you have it
made  -   just drive a IR led from the output of the Rx to optically drive
the IR unit in the car from a metre or so away.




.............     Phil



Re: Convert IR remote to RF remote


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Great idea.  I could mount the RF reciever on the cargo barrier between
the seats and it will have a good "view" of the deck.  Then I don't even
need to open the deck up.  Now the question is, does anyone know where I
would find a Tx/Rx combo that can handle 50 kb/s data rate?

Matthew


Re: Convert IR remote to RF remote


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have it
optically drive

between
even
where I

These modules can do 200kbit/sec:

http://www.commlinx.com.au/tlp916a.htm
http://www.commlinx.com.au/RLP916A.htm

Perhaps you could also consider an IR repeater? Place the IR receiver
of the repeater in a good location (such as the roof area between the
sun visors?) and have the IR transmitter sitting in the boot with your
stereo. That way it's passive and you're not modifying anything except
the car (slightly :) )


Re: Convert IR remote to RF remote


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What about if the data rate was faster, say 120 kb/s or more?  If the
data rate was fast enough, it could replace the IR signal with the RF
one couldn't it?  If that is the case I will have to look for something
with faster data rates.  I don't really want to go poking around too
much inside the deck itself so I was hoping for a simple solution at
least at the reciever end.  I don't mind so much playing around with the
remote 'cause they are nice and cheap.

Matthew


Re: Convert IR remote to RF remote


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Sorry I didn't think it posted the first time.

Matthew


Re: Convert IR remote to RF remote



Matthew Gunn wrote:
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convert an
frequency
didn't
the
in


Hi Matthew,
I don't think you will be able to connect the IR led output directly to
the RF transmitter as the led is usually modulated @ around 40khz.
Also connecting the output of the reciever to the photodiode probably
won't work as there is normally a 40khz filter/amplifier for the
photodiode receive circuit.

You would probably need to drive the transmitter from the unmodulated
signal and connect the output of the reciever after the
amplifier/filter.

Most RF signals are also coded with something like a manchester code to
improve reliability so I don't even like the idea of RF transmission of
the unmodulated signal.

I think you will find the answer to your question is "near impossible".
Regards,
Dean.


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Shit.  Oh well.  Looks like I'll have to make do how it is.  I never
have understood why manufacturers put an IR remote in a car stereo.  I
could understand a RF remote but IR is a joke.  The only line of sight
to the deck is out the hatchback, between the two seats.  This doesn't
really allow many situations where I can actually use the remote to do
anything.

Cheers anyway

Matthew


Re: Convert IR remote to RF remote



< snipped-for-privacy@impartsp.com.au

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  **  You better not buy a radio control system for models then   -   most
just switch the carrier on and off with a simple pulse position modulation
with a 50 Hz repetition rate.   The  FM variety  just shift the frequency up
a few kHz with the same modulation pattern.

 No way that could ever work reliably ..........





............    Phil



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Re: Convert IR remote to RF remote



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most
modulation
frequency up

Actually I think you will find that most OLD radio control systems for
models use simple PPM and any corruption of the stream might only cause
the servo to jitter briefly until the next stream comes along (I
designed the RC encoder for Silicone Chip transmitter).  New RC control
systems use PCM to improve reliability and have error detection.
Regards,
Dean.


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**  Err  -   that is just what I wrote.

 Except that  PPM  ( in either AM or FM versions ) is still the most common
method in use by far.


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**  So it works reliably  -  despite in band interference - because of code
repetition.

     Guess what an IR remote does too ???




................   Phil



Re: Convert IR remote to RF remote


Old model remote control systems used PPM, New and advanced systems use
PCM, ever wondered why ??.

Also the IR remote stops transmitting as soon as you release the switch
therefore it's not continuous repetiton.  PPM systems were used for
analogue systems not for digital code transmissions that if corrupted
could cause very strange actions like turning the CD player off.  All
the RF links for things like car alarms use some kind of coding like a
manchester code.

Regards,
Dean.


Re: Convert IR remote to RF remote





**  Now the snipping  MANIAC  snips out the  ENTIRE  context  !!!!

   So I will put it all back:


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**  Err  -   that is just what I wrote.

Except that  PPM  ( in either AM or FM versions ) is still the most common
method in use by far.


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**  So it works reliably  -  despite in band interference - because of code
repetition.

Guess what an IR remote does too ???


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**  And new ones still do  -  since the method has proven to work so well.


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**  Well, since PPM works so well, fixing it not one of them.


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**  But code repetition it is.


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**  IR  and  PCM radio control systems use code repetition too.


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**  Manchester code simply allows the clock frequency to be extracted from
the code.

Guarding against data errors requires redundancy -  or repetition.


 Now piss off    -   you PITA know nothing pedant.



.............   Phil





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Maybe you would like to advise us all why PCM is used over PPM then if
not for improved reliability (stops servo jitter).

Manchester code transmits 01 for logic 0 and 10 for a logic 1 so there
are a number of illegal codes which can be rejected, therefore guarding
against data errors.

Anyway as your obviously not a very nice person I no longer care to
enlighten you.

Dean.


Re: Convert IR remote to RF remote



< snipped-for-privacy@impartsp.com.au


**  Snipping posts and all context out of sight is a usenet CRIME.


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 **  A  PITA wanker like you cound not  "enlighten"  a dead dog .

      Bugger off.



........... Phil



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which, if your plant isnt an integrator, is a real problem - and even if
the plant is an integrator, its often still a bad thing. eg look at the
lengths astronomers go to to reduce cogging torque in scanning telescope
positioning systems.

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yep. built-in redundancy. Although its generally only the first element
in providing one of Claude Shannons so-called noiseless binary
communication channel. I once did some work on a military remote firing
device for explosives that could detect and correct 9-bit errors, in a
16-bit data stream. Turns out that inadvertently firing off bloody great
piles of high explosive is to be avoided :)

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Empirical evidence suggests he's a quasi-sentient used colostomy bag.
Dont let his drivel put you off posting useful information, others read
NGs too.

Cheers
Terry

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