Reading remote control signals without IR reciever

Projects General Guidance
1

I am attempting to use an old Phillips remote control as a button matrix. I do not want to make use of an IR receiver, I am simply trying to read straight from the PCB of the remote.

My first thought was to remove the IR LED and connect outputs of the LED to the Arduino with a pull-up resistor like so:

image
image721×656 34.6 KB

I then tried to use the IRremote library (GitHub - Arduino-IRremote/Arduino-IRremote: Infrared remote library for Arduino: send and receive infrared signals with multiple protocols) to read the signals from the remote, as I figured the outputted signal should be the same as what a IR receiver would see if I were to use one. This gave me inconsistent results. When I run the included ReceiveDump software, the monitor shows bit lengths and codes that are different each time I press the same button on the remote.

Any ideas why this would happen? Does the library just not support the remote codes, or am I misunderstanding the way IR signals work?

2

Not my aera of expertise but it might be the protocol that is used by the remote. I have an old remote that supports a number of protocols; they are all unknown to me. In some of those protocols, I receive varying 'keys' for the same key on the remote.

Note that this is with a remote that still has the IR functionality.

3

The remote sends code on a modulated 38kHz carrier.  The common IR receiver strips out the 38kHz leaving only the code to be interpreted by whatever.  What you're getting is the modulated signal, the narrow pulses in the rectangles below. 

image

1 Like
4

An interesting idea. Here SB-Projects - IR Index there is very good information about IR remote control. A few years ago I wrote a short program for managing a remote control. Now I changed my code to read the signal directly from the remote control and to filter the modulation with frequency 38kHz. I use an Arduino Nano and some old 5-button remote control with NEC protocol.

// Идеята е сигнала да се взима с кабел директно от дистанционното, което да се ползва като клавиатура с интерфейс по само 1 пин.

const byte IRpin = 2; // pin2 interrupt0 ● pin3 interrupt1

volatile boolean remote = false;
volatile unsigned long irCode = 0;

/*
  ATmega328
  VCC = 2.7V to 5.5V
  Input low voltage, except XTAL1 and RESET pin
  VIL –0.5 +0.3VCC V
  Input high voltage, except XTAL1 and RESET pin
  VIH 0.6VCC VCC + 0.5 V

  IR YS-199 5 button (PCB 15 button) DW6122-82 inside (with 47kΩ on CRS pin) NEC protocol

  Модулацията с честота 38kHz (~26.32µs) да се филтрира програмно.
*/

void remoting () // wired YS-199 NEC
{
  if ( remote )
  {
    remote = false;
    unsigned long T;
    for ( byte n = 0; n < 32; n ++ )
    {
      do
      {
        T = pulseIn ( IRpin, HIGH, 2200 );
      }
      while ( T < 64 );
      bitWrite ( irCode, n, T > 1120 );
    }
  }
}

void setup ()
{
  Serial.begin ( 115200 );
  Serial.println ( F ( "\n\tReady for keyboard reading!\n" ) );
  pinMode ( IRpin, INPUT_PULLUP );
  attachInterrupt ( digitalPinToInterrupt ( IRpin ), remoting, FALLING );
}

void loop ()
{
  if ( irCode )
  {
    Serial.println ( irCode, HEX );
    irCode = 0;
  }
  delay ( 40 );
  remote = true;
}

/*
  Serial Monitor

  EB14FF04
  E817FF04
  E31CFF04
  FE01FF04
  FD02FF04
  FC03FF04
  FB04FF04
  FA05FF04
  F906FF04
  F807FF04
  F708FF04
  F609FF04
  EF10FF04
  FF00FF04
  EE11FF04
*/

IR KBD
IR KBD1590×953 11.1 KB

It worked for me and it works well.

5

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.