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From: KevinJ93 <kevin_es@whitedigs.com>
Newsgroups: sci.electronics.design
Subject: Re: Ir remotes
Date: Mon, 20 May 2024 14:43:18 -0700
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On 5/20/24 1:07 PM, LM wrote:
> On Mon, 20 May 2024 00:01:18 -0700, Don Y
> <blockedofcourse@foo.invalid> wrote:
> 
>> My understanding is that Ir remotes modulate an Ir "carrier" signal
>> in a particular pattern to express a particular "code" corresponding to
>> the key pressed/held.
>>
>> And, that different "chipsets" use different carriers and encodings.
>>
>> Is there a front-end that is tuned to the particular carrier
>> in the receiver?  Or, is all of this done "digitally"?
>>
>> I.e., with a fast-enough (Ir) photodetector, should I be able to
>> decode ANY signal from ANY "remote"?
>>
>> Said another way, is the fact that a particular device ONLY
>> recognizes a particular remote related to its use of a particular
>> chipset (or, equivalently, decoding algorithm in software)?
>>
>> [The former would be hard to change but the latter should be relatively easy]
> Are you looking for something like this:
> https://en.wikipedia.org/wiki/RC-5
> 
> Years ago  a long range remote used IR leds which could take 1A
> current, but only for a microsecond or so.  Microsecond pulses were
> modulated with 33-38kHz "carrioer" and that was keyed with data,
> around 1-2kHz.
> There are dedicated deceiver modules which  can output that data

Such as:

https://cdn-shop.adafruit.com/datasheets/tsop382.pdf

They do all the analogue processing and just output a datastream to the 
decoder.

Typically the bitstream runs about 1kbit/s so easily decoded by software.

The transmitter can also be handled by driving an LED from a timer 
programmed to output the 38kHz then doing on-off keying (OOK) to provide 
the modulation. Minimal hardware outside a microprocessor is required.

kw