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I have an IR receiver and an IR LED I got from a kit (I don't have the datasheets for them).
I uploaded an Arduino sketch to record my A/Cs IR codes. Those were NEC encoded 32bit integers.
After recording the codes, I tried retransmitting them. The A/C unit failed to detect the signals.
Troubleshooting a bit, I sent the code from the Arduino the receiver sketch from the previous step - it received them successfully.

All the above steps used the IRRemote Arduino library

The question is, what could explain this behavior? A few possibilities I had in mind:

  1. IR frequency. Could it be that the detection circuit worked with the default settings but transmitting wouldn't?
  2. IR wavelength. Any chance the A/C side doesn't detect my IR pulses at all?
  3. Decoding/Encoding of the NEC protocol in IRRemote. If there is no standard for the NEC protocol, the Arduino and A/C implementation might be a little different.
  • 1
    Is it an NEC air conditioner? I think the IR library has a "raw" mode - you could try that, which more exactly replicates exactly what it received. I think your solutions (1) and (2) are a little unlikely, but feasible. – Nick Gammon Sep 27 '15 at 7:02
  • You could try a different library: tech.cyborg5.com/irlib – Nick Gammon Sep 27 '15 at 7:04
  • 4. range. The ir led you use could be far weaker than the one in the remote. Try placing the arduino right next to the AC unit. – Gerben Sep 27 '15 at 9:16
  • @NickGammon It's not a NEC air conditioner. It just uses the NEC IR protocol. As for your RAW mode suggestion, I tried it, but the raw receiver generates both negative and positive values. I'll try to give it another try and try the other library as well. Thanks! – omribahumi Sep 27 '15 at 10:13
  • HI I have put my answer on the link below. stackoverflow.com/questions/44528781/… Please let me know if it works for you. Let me know if you need help. – Ourang-Zeb Khan Aug 30 '17 at 8:15
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Hi i have done the same thing. I was using this to get the AC codes for the GREE AC. I find it with two weeks struggle and a forum called AnalysIR. If you find any issue in this code below or method let me know.

AC codes are usually long and those doesn't come right with the code which you used above so i am giving you the sample code to run in the Arduino sketch so that you can test.

   #define LEDPIN 13
  //you may increase this value on Arduinos with greater than 2k SRAM
  #define maxLen 800

       volatile  unsigned int irBuffer[maxLen]; 
       //stores timings - volatile because changed by ISR
       volatile unsigned int x = 0;
       //Pointer thru irBuffer - volatile because changed by ISR

     void setup() {
     Serial.begin(115200); //change BAUD rate as required
     attachInterrupt(0, rxIR_Interrupt_Handler, CHANGE);
    //set up ISR for receiving IR signal
     }

 void loop() {
   // put your main code here, to run repeatedly:

   Serial.println(F("Press the button on the remote now - once only"));
    delay(5000); // pause 5 secs
  if (x) { //if a signal is captured
digitalWrite(LEDPIN, HIGH);//visual indicator that signal received
Serial.println();
Serial.print(F("Raw: (")); //dump raw header format - for library
Serial.print((x - 1));
Serial.print(F(") "));
detachInterrupt(0);//stop interrupts & capture until finshed here

for (int i = 1; i < x; i++) { //now dump the times
  if (!(i & 0x1)) Serial.print(F("-"));
  Serial.print(irBuffer[i] - irBuffer[i - 1]);
  Serial.print(F(", "));
                     }

   x = 0;
   Serial.println();
   Serial.println();
   digitalWrite(LEDPIN, LOW);//end of visual indicator, for this time
   attachInterrupt(0, rxIR_Interrupt_Handler, CHANGE);//re-enable ISR for            receiving IR signal
        }

      }

  void rxIR_Interrupt_Handler() {
    if (x > maxLen) return; //ignore if irBuffer is already full
     irBuffer[x++] = micros(); //just continually record the time-stamp of signal transitions

    }

Once this is done you will get the right code to send it to the AC.

A little Tricky part

once you will receive the codes of raw values you will have to little modify it for example i got the raw values and i converted it into the array.

What i received for example Raw (16): -27750, 4464, 696, 1612, 692, 516, 688, 516, 688, 1620, 692, 512, 692, 1612, 696, 1612, 692, 512, 692, 516, 688, 1616, 696, 1612, 692, 512, 696, 512, 692, 512, 692, 512, 696, 512, 692, 512, 692, 512, 696, 512, 692, 512, 692, 512, 696, 1612, 692, 1612, 692, 516, 688, 516, 692, 516, 688, 516, 688, 516, 692, 1612, 692, 516, 688, 1620, 688, 516, 688, 520, 684, 1620, 660, 544, 664, 19960, 628, 1680, 628, 1676, 628, 580, 628, 1676, 628, 580, 624, 580, 628, 576, 628, 580, 628, 584, 620, 576, 628, 580, 628, 576, 628, 576, 628, 580, 624, 1680, 628, 580, 624, 580, 628, 580, 624, 580, 628, 576, 628, 580, 624, 580, 628, 576, 628, 580, 628, 576, 628, 580, 624, 580, 628, 576, 628, 1680, 624, 580, 628, 1676, 628, 1680, 628

To Convert the above raw values into array remove first value which is -27750 and put 3800 instead of that. Below is the array sample.**

unsigned int data[] = {3800, 4464, 696, 1612, 692, 516, 688, 516, 688, 1620, 692, 512, 692, 1612, 696, 1612, 692, 512, 692, 516, 688, 1616, 696, 1612, 692, 512, 696, 512, 692, 512, 692, 512, 696, 512, 692, 512, 692, 512, 696, 512, 692, 512, 692, 512, 696, 1612, 692, 1612, 692, 516, 688, 516, 692, 516, 688, 516, 688, 516, 692, 1612, 692, 516, 688, 1620, 688, 516, 688, 520, 684, 1620, 660, 544, 664, 19960, 628, 1680, 628, 1676, 628, 580, 628, 1676, 628, 580, 624, 580, 628, 576, 628, 580, 628, 584, 620, 576, 628, 580, 628, 576, 628, 576, 628, 580, 624, 1680, 628, 580, 624, 580, 628, 580, 624, 580, 628, 576, 628, 580, 624, 580, 628, 576, 628, 580, 628, 576, 628, 580, 624, 580, 628, 576, 628, 1680, 624, 580, 628, 1676, 628, 1680, 628, };

Now sending these values to the IR transmitter use this code below.

      #include<IRremote.h>
       IRsend irsend;
       int KHz = 38;                    // default frequency

      unsigned int data[] = {3800, 4464, 696, 1612, 692, 516, 688, 516, 688, 1620, 692, 512, 692, 1612, 696, 1612, 692, 512, 692, 516, 688, 1616, 696, 1612, 692, 512, 696, 512, 692, 512, 692, 512, 696, 512, 692, 512, 692, 512, 696, 512, 692, 512, 692, 512, 696, 1612, 692, 1612, 692, 516, 688, 516, 692, 516, 688, 516, 688, 516, 692, 1612, 692, 516, 688, 1620, 688, 516, 688, 520, 684, 1620, 660, 544, 664, 19960, 628, 1680, 628, 1676, 628, 580, 628, 1676, 628, 580, 624, 580, 628, 576, 628, 580, 628, 584, 620, 576, 628, 580, 628, 576, 628, 576, 628, 580, 624, 1680, 628, 580, 624, 580, 628, 580, 624, 580, 628, 576, 628, 580, 624, 580, 628, 576, 628, 580, 628, 576, 628, 580, 624, 580, 628, 576, 628, 1680, 624, 580, 628, 1676, 628, 1680, 628,
        };


    void setup() 
   {
     Serial.begin(9600);   
     irsend.enableIROut(38);
   }

    void loop()
   {

    for (int i=0; i<1 ; i++){
    irsend.sendRaw(data, sizeof(data) / sizeof(int),38 ); 
    delay(40);
          }


 }

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