Author Topic: How does a 38khz IR detector differ from 40khz, etc?  (Read 2672 times)

0 Members and 1 Guest are viewing this topic.

Offline MaltaeronTopic starter

  • Full Member
  • ***
  • Posts: 65
  • Helpful? 0
How does a 38khz IR detector differ from 40khz, etc?
« on: March 19, 2008, 10:26:13 PM »
What is the difference? I am using 38khz, and I here that is the standard for TV remotes as well.

Also, what is it about being a modulated signal?

I have a setup with an IR detector and LED, no ICs, what is the basic principal for communicating like this?

Thanks,
Confused Person

Offline paulstreats

  • Supreme Robot
  • *****
  • Posts: 1,381
  • Helpful? 21
Re: How does a 38khz IR detector differ from 40khz, etc?
« Reply #1 on: March 20, 2008, 03:10:29 AM »
buy an serial to ir encoder/decoder module to do it for you like this:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010407

It will be extremely difficult and ultimately far more expensive to do it yourself. Without it  you would need a lot of additional circuits built.

Offline Steel_monkey

  • Full Member
  • ***
  • Posts: 85
  • Helpful? 0
Re: How does a 38khz IR detector differ from 40khz, etc?
« Reply #2 on: March 20, 2008, 02:16:52 PM »
Here is a little explanation of how this IR receivers work http://www.societyofrobots.com/member_tutorials/node/102 ( in the area a little different from communications, but I believe it will be clear). The basics: we modulate our bit samples with 40 KHz (or 38 KHz, it is relatively wide-band, so 40 KHz receiver will most likely sense 38 KHz signal). Something like that: we a re sending  10101 pattern
                          1                                     0                               1                                    0                              1
              ______________________                              ______________________                                     ___________________
 _______|                                      |________________|                                      |____________________|                                 | _
and modulate IR LED intensity.
              __  __  _   __  __  _   __                                 __  __  _   __  __  _   __                                         __  __  _   __  __  _   __
________| |_| |_| |_| |_| |_| |_| |___________________| |_| |_| |_| |_| |_| |_| |_______________________| |_| |_| |_| |_| |_| |_| |__

Receiver demodulate it into initial pattern (text is formatted automatically, really second and third "one" bits look loke the first one)
« Last Edit: March 20, 2008, 02:19:51 PM by Steel_monkey »

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,660
  • Helpful? 169
    • Society of Robots

 


Get Your Ad Here

data_list