Detecting IR frequencies

Guest
I want to give my bedroom the special treatment for CHRISTmas and
decorate it up. I have one of those Wild Planet (the company that makes
all that spy gear for kids) motion detectors. I am wondering if there
is some way to find out what frequency(without buying an ir detector
from Radio Shack, the remote for my Altec Lansing iM3 Ipod speakers
told the Ipod to play, so that whenever somebody walked into the room
Manheim Steamroller, and other Christmas music, would start playing.
 
ngdbud@hotmail.com wrote:
I want to give my bedroom the special treatment for CHRISTmas and
decorate it up. I have one of those Wild Planet (the company that makes
all that spy gear for kids) motion detectors. I am wondering if there
is some way to find out what frequency(without buying an ir detector
from Radio Shack, the remote for my Altec Lansing iM3 Ipod speakers
told the Ipod to play, so that whenever somebody walked into the room
Manheim Steamroller, and other Christmas music, would start playing.
Click to expand...
Most remotes are at 38 kHz.... See http://www.lirc.org for an
interesting read on remotes. There are directions on the site for
building transmitters. It's not trivial - but it is fun.
 
ngdbud@hotmail.com wrote:
38 khz? Are you saying these remotes run off AM not FM?

I don't know --- all I know is that is stated frequency of the receivers
Click to expand...
I use and they work.... Check out vishay 1738
http://www.vishay.com/docs/82030/82030.pdf - I have made several of
these and they work with common IR remotes.

--Yan
 
(ngdbud@hotmail.com) writes:
38 khz? Are you saying these remotes run off AM not FM?

Why would you get that from what he said? It could mean a carrier
Click to expand...
frequency for an AM signal, or the center frequency for an FM signal.

Besides, if it was amplitude modulated, more likely you'd just see
a modulation of the IR LED, rather than have a subcarrier feeding it.
But there are very good reasons for not doing it that way, because
it will mean the circuitry is more likely to be interfered or confused
with by light levels in the room (or for that matter random light levels
could cause the unit to change channels). Finally, when you start
amplitude modulating an LED, you can't set things for optimum performance.

Which means that it will likely be FM, because it doesn't matter if
you directly modulate the LED or modulate a carrier that feeds the LED.

With FM modulation, the feed to the LED is constant, hence it can
be set for maximum output.

Michael
 
ngdbud@hotmail.com wrote:
38 khz? Are you saying these remotes run off AM not FM?
Click to expand...
The method of modulation does not depend on the frequency. You are
probably thinking of commercial radio where FM radio is around 100MHz
and AM is ~100kHz.

Most remote controls have very simple modulation. There is a carrier,
which is probably around 38kHz. This carrier is switched on and off (at
a frequency much lower than 38kHz) to give a pattern of pulses which
corresponds to the button you pressed. I'm not sure how you would find
this pattern unless someone else has done a similar project - try a
Google search.

Gareth

--
-----------------------------------------------------------------------
To reply to me directly:

Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris
 
I would hazard a guess that the motion detector uses "Passive IR" or "PIR"
detection, which is essentially a heat sensor that registers the change in
heat in its field of view and sounds an alarm. This is the principle that
the vast majority of home security motion detectors, automatic lamp sensors,
etc. employ.

If my assumption is correct, there's no emitted IR signal to detect. The
Wild Planet box is simply a sensor and makes noises when it detects motion.

I'm basing this on what I found at this link:

http://www.toys2wish4.com/spydesi.html

TJL


<ngdbud@hotmail.com> wrote in message
news:1126737693.007642.79790@f14g2000cwb.googlegroups.com...
I want to give my bedroom the special treatment for CHRISTmas and
decorate it up. I have one of those Wild Planet (the company that makes
all that spy gear for kids) motion detectors. I am wondering if there
is some way to find out what frequency(without buying an ir detector
from Radio Shack, the remote for my Altec Lansing iM3 Ipod speakers
told the Ipod to play, so that whenever somebody walked into the room
Manheim Steamroller, and other Christmas music, would start playing.
Click to expand...
 
On 2005-09-14, ngdbud@hotmail.com <ngdbud@hotmail.com> wrote:

I want to give my bedroom the special treatment for CHRISTmas and
decorate it up. I have one of those Wild Planet (the company that makes
all that spy gear for kids) motion detectors. I am wondering if there
is some way to find out what frequency(without buying an ir detector
from Radio Shack, the remote for my Altec Lansing iM3 Ipod speakers
told the Ipod to play, so that whenever somebody walked into the room
Manheim Steamroller, and other Christmas music, would start playing.
Click to expand...
the frequency of the IR is the leasst critical thing,
what you need to track down is the exact IR pulse sequence the remote sends.

if you don't want to buy an IR detector open up the remote and attach an
apropriiate device to the LED and record the pulses it gets.

Bye.
Jasen
 
On 2005-09-15, ngdbud@hotmail.com <ngdbud@hotmail.com> wrote:
38 khz? Are you saying these remotes run off AM not FM?
Click to expand...
No he's wrong they operate at around 320THz :)

the IR beam is amplitude modulated (well pulsed would be more acurate)
at around 38KHZ and the 38KHZ itself is pulsed to send
a digital signal coressponding to t he keypress etc that the remote
wants to send.

there may be remotes that do FSK or PSK on the 38KHZ "carrier" or use some
other frequency...


--

Bye.
Jasen
 
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