IR receiver TSOP34838 problem

Discussion in 'The Projects Forum' started by aleksazr, Mar 13, 2014.

  1. aleksazr

    Thread Starter New Member

    May 16, 2010
    14
    0
    I've been playing with the TV remote control, capturing the data sent.
    This is my second try, btw. Last time was two years ago, and now I'm failing at the same place...

    As shown here, RC-5 remote repeats a code every 114ms.
    That works, every 110ms I get something...

    That something should be 14 bits, lasting 25ms, but I only get a few 1s and 0s lasting less than 2ms.
    (see picture)

    I'm using TSOP34838. On the second page of that PDF there is an APPLICATION CIRCUIT, quite simple.
    I've used 100E and 4u7 for R1 and C1.
    I've tried two TSOP34838s, both (not) working the same.

    The circuit is simple, but is not working and I have no idea why...
    Anyone had a similar experience?
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,282
    1,236
    I could be wrong, but I think with the Phillips protocol the gap and the burst length are the same and your sensor needs the gap to be 4X the burst length.
     
  3. aleksazr

    Thread Starter New Member

    May 16, 2010
    14
    0
    Well, it says here (bottom of pages 1 and 5) that it supports RC-5.

    The problem was that the remote control actually used ITT protocol, and TSOP34838 simply can't receive that.
    Someone suggested that I should sample both TX and RX diodes, see picture.

    Luckily, the remote is a universal one, so I'll look for a code that uses RC-5.

    Thanks for your input.
     
  4. aleksazr

    Thread Starter New Member

    May 16, 2010
    14
    0
    OK, found an RC-5 code on my remote, and immediately found my next problem :)

    RC-5 sends 0 as 10, and 1 as 01. So 00 and 11 should not exist, right?
    Even though I've pressed a key several times, I always get C1 to be 11, and either S2 or T to be 00.
    Why is that?
     
  5. hexreader

    Active Member

    Apr 16, 2011
    250
    82
    Your receive signal is inverted (which is normal).

    Shift the dotted lines in your diagram left by one notch and all will become good
     
  6. aleksazr

    Thread Starter New Member

    May 16, 2010
    14
    0
    Thanks, that sorted things out.
     
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