OT? Infrared control and such

[Theo]

Someone else might give you a better ( indepth ) explanation, just scanning
the surface here.

Roughly the picture looks like this.
Infrared remotes use a LED/Foto-transistor (FT) pair.
FT are transistors, LDR are resistors.
Where LDRs respond slowly to light changes, FTs respond fast.

This makes it possible to modulate the signal from the transmitter and let
the receiver only respond to that signal.
Think of it like radio, al kinds of signals and noise in the air, but still
your receiver can pick the one channel you want to hear.


Cheers Theo


----- Original Message -----
From: <CCartCat at aol.com>
To: <synth-diy at node12b53.a2000.nl>
Sent: Thursday, April 20, 2000 5:36 PM
Subject: OT? Infrared control and such


> Hi--
>
> Been thinking about infrared transmission/reception in remote controls for
> VCR's etc. and wondering how that technology relates to LED/LDRs, the
whole
> homebrew vactrol thread.  Neither being an engineer/tech nor someone with
> extended sub-spectrum vision, I'm generally in the dark on this.
>
> There are (roughly speaking) infrared equivalents of LED/LDR's at work
here,
> yes?
>
> Is there a fair amount of natural ambient infrared in our environment as
> there is visible light?
>
> I gather from using a remote in proximity to an electric guitar and
picking
> up the electronic noise that the remote is sending pulses to the VCR via
> infrared flashes.  While this is probably the logical format of commands
> received by the VCR, is this also to cut through any ambient infrared in
the
> room?
>
> Wireless headphones for quiet TV viewing use infrared also, right?  But I
> would imagine it would be analog and thus subject to, I dunno, a hot
turkey
> sandwich swamping out the signal.
>
> Getting closer to home, that is, topic, the D-Beam controller uses
infrared,
> correct?  Any idea how?  (Does infra. reflect?)
>
> Generally, I'm trying to get an idea of how these other infrared devices
work
> so I'd have some informed idea how one would use infrared (much) more
simply
> in an analog/CV, homebrew vactrol, flashing goofytech theatre of light
sort
> of way.  It'd be nice to know, for instance, about the nature of
> infrared--like whether it's a good idea to put a infrared LDR near
something
> hot unless you want a high infrared offset that any other source would
have
> to spike above.
>
> Thus, all these questions . . . <g>
>
> Thank you for your time,
> Kevin Seward