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 Post subject: Question About IR Reciever, re: PICAXE PRIMER June 2012
PostPosted: Sat Jun 09, 2012 1:59 pm 

Joined: Tue Aug 17, 2004 12:01 am
Posts: 43
Location: Beaumont, TX
In reading the referenced article in the June 2012 issue of Nuts&Volts, I was particularly interested in the discussion on the recommended IR receiver in the first two paragraphs. I am working on a device that uses such a receiver and I want one that would work with as many existing TV/VTR/BluRay/etc. remotes as possible. In short, I want a universal IR receiver or as close to that as possible. It seems to me that my requirements are very close to that required in the project in the article. I am presently looking at the Vishay TSOP31x38 series of receivers.

In earlier work the author, Ron Hackett, said he used a Panasonic PNA4602 IR receiver but that part is now discontinued. He further states that he is testing a Vishay TSOP34338 which meets all three of his requirements (pin for pin compatible, 38 KHz operation, and no additional parts). It seems these requirements are primarily centered around keeping an existing PC board layout. I will not have that problem as I have figured out a layout with some extra pads that will accomodate all the IR receivers that I have data sheets for. As far as I can tell from the data sheets, the specs for the TSOP31xxx series and the TSOP32xxx & TSOP34xxx products is the latter are in smaller packages. The only specs that seem to differ is the ones that would depend on the actual package. And the pin-outs are different, but that could be package related too.

One thing I have been interested in is the ability to cover a range of frequencies. I get the impression that 36 - 40 KHz would cover most devices and the data sheets show some bandwidth in this regard. Is 38 KHz the best choice? I have also seen 40 KHz devices recommended for general use.

What I would like is a discussion of the various choices and which would be best for a device that is intended to work as well as possible with as many of the existing remotes as possible.

One more question, the Vishay block diagrams for all of these receivers show an internal pull up resistor on the data output pins. Yet, in the article he shows an external pull up of 4.7K. Why? Is that a leftover from the Panasonic device and not needed for the Vishay? Or is it needed for some other reason?



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Paul A.
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 Post subject: Re: Question About IR Reciever, re: PICAXE PRIMER June 2012
PostPosted: Tue Jun 12, 2012 12:16 pm 
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Joined: Wed Aug 03, 2011 10:03 am
Posts: 5
Hi Paul,

I haven't experimented with IR frequencies other than 38kHz, but if you want to test devices between 36kHz and 40kHz, a 38kHz receiver would be your best bet because it's right in the middle. Sensitivity will drop off as you move away from 38kHz, so the usable range will also decrease. If you can find an IR receiver that's centered on 38kHz, but has a wider band width, that might be better. In any case, you will need to do range testing at each of the frequencies you want to use.

The 4.7k pull-up resistor that I think you are referring to (Figure 3, p.16 in the article) is for the DS18B20, not the Vishay IR receiver, which doesn't require any external parts.

Ron


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 Post subject: Re: Question About IR Reciever, re: PICAXE PRIMER June 2012
PostPosted: Wed Jun 13, 2012 10:32 pm 

Joined: Tue Aug 17, 2004 12:01 am
Posts: 43
Location: Beaumont, TX
Ron,

Thanks for the reply. My problem is I am trying to design a "universal" receiver that can cover as many existing remotes as possible. I am sure there are tens or hundreds of thousands of them out there. I can't test them all and I know it is an impossible goal to be compatible with all of them. I was just hoping someone would have some knowledge of the most popular frequencies in use.

I guess I am going into uncharted waters here. I do plan to do some testing with all the remotes I can get my hands on.



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