Sending IR (NEC)-Signals with Arduino

Question

I have an Arduino Micro where I want to control a display with IR commands. So the Arduino should send the IR commands to the display.

I have found a library "Arduino-IRremote", which I am using to transmit Commands to the display. The display works perfectly with its remote control, however I can't get it accept signals from my Arduino.

Now the special part about my setup is, that I do not use a "classic" IR transmitter. Instead i uset an IR cable, which is connected to "IR-In" of the display. So no LED - only a wired connection. The IR-cable consists of 3 wires. 2 for power supply (VIN and GND) and one is for the data connection. The wire with the data connection is connected with the Arduino PWM pin 3 (like it is said on the example in the linked library), but I tried all other pins anyway.

#include <IRremote.h>
IRsend irsend;

void loop() {

  for (int i = 0; i < 2; i++) {
    digitalWrite(RXLED, HIGH);
    irsend.sendNEC(0x004eff71, 32);
    Serial.println( "sendNEC 00 4E FF 71" );
    digitalWrite(RXLED, LOW);
    delay(40);

  }
  delay(1000); 
}

004eff71 is a NEC-Command from the original remote control

Now can somebody tell me, what I'm doing wrong? The program compiles and the LED lights up, everytime it should send the NEC-command. But still the display receives nothing. What is wrong?

Answer 1

It isn't working probably because the output of the Arduino isn't simply an on/off signal.

That library uses a pulse width modulated output on the Arduino to drive an LED. When the LED is "on" the signal driving it is actually pulsing at a very high rate.

I don't know what all you'd have to change to make that work with a direct wired connection.

Another thing that might becausing problems is that without checking, you can't be sure that the signal level you are sending matches the levels that the IR receiver would normally produce.

Answer 2

It would help to know the specifications of the IR input on the device you're trying to control but after a bit of googling it looks like most of them are just expecting a connection to an IR receiver. I found a link to what appears to be a common one, TSOP22.., TSOP24.., TSOP48.., TSOP44.. and here's a link to the data sheet (http://www.vishay.com/docs/82459/tsop48.pdf). If you check the Vo on page 2 it shows 0-5V. You didn't mention if you're using a 5V or 3V Arduino so that could be an issue.

The PWM outputs do in fact generate square wave signals so at first glance this does not look like a hardware issue (assuming it is wired correctly for the IR input on your equipment).

I'd start taking a look at the data you're trying to send. I haven't looked into the library you mentioned and hopefully it contains a sample to show how to properly initialize the library and send data. Maybe instead of first byte first it needs to be sent first byte last or requires a fixed number of bytes to send...

Providing more details about your project you might get a better answer.