Re: improving range?

[Bill P. <goa...@ya...>]

This will anger alot of people, and I AM duly
impressed with Milan's IRdA driver (whoa that is
cool!) but nonetheless... IRdA should never be used as
a consumer IR receiver. 

It's like complaining to Dodge that your Viper has
poor traction in snow. Yea it's a car and yea you can
drive it on snow. Just not very well nor very far. :-)

I'm impressed you got it to work because so many
can/will not. But as you discovered it's range leaves
something to be desired for a remote control receiver
app. It must be said: It was never intended for this. 

In your case you're using it in a projection TV room,
so there's probably not much sunlight here because of
glare. But in a brightly lit room or for controlling
your MP3 player thru the window from outside on the
patio, it will never work. Don't even try, anyone
reading this. (and if you are the 3rd person to tell
me all the tricks and stupid stuff you did to avoid
making a $5 serial receiver, don't bother. I'll say
"good for you!" right here. :-)

As for range with a homebrew I can easily get 6m, most
units 10m... sometimes more. With a standard remote.
My test zone is 6-7m... anyone that can afford a house
and TV big enough to sit >6m from the screen can pay
an AV consultant.
 
IR protocols use a carrier frequency and if you match
your transmitting remote to an IR protocol that's at
the target bandpass of your detector module you'll get
10x the range of that IRdA port, in sunlight too.

Another thing is wavelength. Most IR remote LEDs are
940nm and so are the detectors for RemCo applications.
But there exist 880nm 850mn, etc. If they don't match
you are severely limiting your range. An 850mn
filtered photodetector will only see ~2% of the light
of a 940mn LED... it might not detect with it touching
the detector!

Since you have a universal remote it's easy. Just set
a 'device' to one of the protocols around your
detector's frequency. For example, if your friend
built the serial detector using the Radio Shack
#276-137 40kHz module I'd suggest using a Sony IR
protocol (which is also 40kHz). If you're using a
38kHz module then maybe RC-5 protocol, etc.

How do you know what IR devices use what protocol, and
what the specifications are for each protocol?
Research. :-) 

And an adapter port or built-in IRdA port is, uh, less
than directional. With a homebrew serial you can
solder it to the end of a 50' wire and place it
anywhere and much farther away and aim it... like at a
wall so it can see the reflected pulses easier. Also
make sure your lircd.conf has the 'frequency' entry
for the remote section. (defaults to 38kHz)

The dissipation and scattering of light that happens
on a bounce shot makes it unpredictable. Even the
paint finish, color, and texture will control how far
the bounce works. Detector height, aim, ambient light
hitting the detector, etc. All are factors. If you're
4m away from a wall you want to bounce directly off of
to go behind you another 3m, good luck dude. That
(almost) never works. Just point your hand over your
head backwards with that remote or use a long wire for
the serial detector and run it up front near the TV
unit.

You can 'loosen up' lirc's detection with eps/aeps in
lircd.conf but this may or may not help. Try running
"xmode2 -t 1" under X and making it fullscreen. See
how much noise the detector is picking up. Walk
around, testing bounce shots and direct aims. At a
certain point the remote's pulsetrain will get
interrupted with a noise spike or not detect a weak
pulse, and there's not much to do but get closer or
use a stronger remote (or shield the detector better)
If while holding a button press you see half of the
rendered streams being hosed, that's probably your
limit right there.

As for replacing it in the case where an IRdA dongle
was, that's a cool idea! But, you're still gonna have
the problem of positioning. If you cannot point the
remote at the computer and must bounce, I highly
suggest a detector on a wire you can run along the
carpet edge and mount 'up front' with the rest.

Sorry for the book, and hope this helps.

(fan of the wall-bounce and under-the-door shots too)

-------------------------

--- Adam Megacz <ad...@me...> wrote:
> 
> I was using lirc for a while with my desktop's
> built-in SIR
> reciever. The range was crappy (1m). Then I attached
> a homebrew serial
> reciever that a friend built for me. Much better --
> now the range is
> several meters.
> 
> Unfortunately, I use a big-screen CRT projector, so
> what I *really*
> want is to be able to bounce the signal off the wall
> (ie face the
> screen, press a button, signal bounces off the wall
> and is received by
> the computer *behind* me). I'm using a radio shack
> 6-in-1 remote
> (rebranded Cinema6, I think) for both my projector
> and my computer,
> and the projector works bouncing it off the wall, so
> I know that the
> remote is strong enough.
> 
> When bouncing off the wall, I still see activity in
> mode2, but lircd
> doesn't interpret it as signals. I can even train
> lircd (via irrecord)
> in bounce-it-off-the-wall mode, but when I do that,
> it generates a
> 'raw mode' config file which doesn't seem to work.
> If I train it by
> pointing the remote at the reciever, it works okay,
> but only when
> pointing it *at* the reciever (not bouncing off the
> wall).
> 
> Anyways, I know the signal is getting to the
> reciever... is there any
> way for me to tell lircd to take the signal it gets
> and just guess
> which button's signature is closest to the signal it
> recieved instead
> of demanding a perfect match? I only programmed 6 or
> 8 butons, so a
> good guess should be good enough...
> 
> Also, since the Cinema6 is pretty popular and is
> programmable-and-learning, can anybody else
> recommend a 'personality'
> with the remote that gets good range with lircd? I
> have it emulating
> some random Sony VCR right now.
> 
> Thanks!
> 

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