Hi,

I am designing an InfraRed link to tx and rx an analog signal over a distance of about 5m.

Can anyone offer any pointers to cct diagrams or other resources I may use as a starting point for this project

Thanks

Stevo

 

What sort of analogue signal?.

Do you just mean a voltage reading?, or something like an audio signal? - and if so, what sort of bandwidth do you require?.

 

I'm actually working on several similar systems, and over the weekend will be working out the details on a quad-opamp band-pass filter. I'll post my results by Monday, so hopefully they will be of use to you.

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Basically it is a 9600 Baud, full duplex data link and has a bitrate of about 57K6bps. Using fdm There are 2 distinct frequency bands 1 for tx and 1 for rx which I can filter easy enough. I was wondering if anyone else has done something similar.

Stevo

 

Well that's a digital signal - not an analogue one :lol:

I'm also a little confused about your speeds? - 9600Baud is usually 9600bps, assuming normal 8N1 type protocols. Or is the vastly increased bps because of error correction added to the data?.

'Normal' IR remote controls work nowhere near that fast, usually only about 2400 or 1200 baud, and you can't normally just send standard serial data across them - you need some kind of coding, Manchester coding is commonly used.

 

Sorry if I am a little vague. There are some sensitivities surround a project I am working on so I'm trying to be as general as possible.
Yes you are correct, what I described was a digital signal, however due to the encoding and modulation mechanism it is presented to layer 1 as an analog signal.

My original question probably should have been "What is the bandwidth of an IR link? Can anyone give me some pointers to good resources I can look up on the subject." 8)

Regards

Stevo

 

A good website for designig remote control applications would be:

www.rentron.com

You can contact their technical support for any question you have, there is a guy called Bruce, who is a calibre in this field. :!:

I myself used the information there to design a Rx, Tx IR system from scratch.

Itay

 

I don't understand why you need two frequecies. For 1 tx + 1 rx you need two beams, so you can use the same frequencies - just switch off the rx each end when you are txing from there to stop 'splatter'.

As Nigel said, you ideally need Manchester coding, but if you can ensure correct signal polarity at the receiver, then you can use baseband signals with normal start and stop bits.