How does a battery powered infrared transmitter work?

[John Harmonic]

Which part of the DC circuit produces the oscillation for infra-red transmission in a remote control for television for example. 

[Klaynos]

The IR LED? 

 

[Strange]

1 hour ago, Klaynos said:

The IR LED? 

True.

But there the light from the LED is also modulated to encode the different commands. I would imagine most of them use a simple microcontroller.

[Klaynos]

1 hour ago, Strange said:

True.

But there the light from the LED is also modulated to encode the different commands. I would imagine most of them use a simple microcontroller.

I don't know, remote controls were around before the advent of small cheap microprocessors. If the non microprocrssor solution works, is reliable and cheap I suspect it's still quite common. Probably something clever with cheap timing chips. 

I'm not sure if the question was about the modulation of the actual photon generation?

[John Cuthber]

There are dedicated chips for this

http://www.unisonic.com.tw/html/IC/39.Remote-Controller-IC.htm

[Strange]

On 27/09/2018 at 8:03 PM, John Cuthber said:

There are dedicated chips for this

http://www.unisonic.com.tw/html/IC/39.Remote-Controller-IC.htm

Thanks for looking that up. (I was too lazy at the time!) They seem to have a limited number of fixed functions. I was thinking more of the "universal" TV remotes which can be set to use one of a large number of different command sets. They could be hardwired but might be easier to make using a simple programmable controller.

[Klaynos]

10 minutes ago, Strange said:

Thanks for looking that up. (I was too lazy at the time!) They seem to have a limited number of fixed functions. I was thinking more of the "universal" TV remotes which can be set to use one of a large number of different command sets. They could be hardwired but might be easier to make using a simple programmable controller.

Ah yeah. I expect you're right. 

You can even get (or at least build) ones that you point other remote controls at and can remember what they receive. 

[Ghideon]

5 hours ago, Strange said:

They could be hardwired but might be easier to make using a simple programmable controller.

Good point, and thereby also easier to add more functions (see below)

5 hours ago, Klaynos said:

You can even get (or at least build) ones that you point other remote controls at and can remember what they receive. 

Yes.

It's been a while but my memory says that i've had three universal remotes; not sure if price tag and production cost or complexity correlate but:
-Cheapest one had a hardcoded set of commands for a set of manufacturers.
-Next had hardcoded set of commands plus the ability to learn new commands by pointing it nose to nose with another remote. (Nice if you bought the replacement remote before the old one was broken)
-Most expensive had a connection for adding new models / IR codes. I believe the high price in this case was not necessarily motivated by production cost. Guesswork: A Programmable controller as stated by @Strange was required anyway, and by allowing en user to connect to it looked more fancy, and retailed at a significantly higher price.

[Sensei]

6 hours ago, Klaynos said:

You can even get (or at least build) ones that you point other remote controls at and can remember what they receive. 

Interesting and easy project for Arduino. IR diode with serial class used to get data on the computer.

#include <Serial.h>
static const int pinIR = A0; // let it be at analog pin...
void setup() {
   pinMode( pinIR , INPUT );
   Serial.begin( 9600 );
}

void loop() {
  int state = analogRead( pinIR );
  Serial.println( state );
}

Then use Tools > Serial Plotter to see what has been received on graph. Press the all TV remote controller buttons one by one.

If the above code will work, the next step could be LCD screen shield with buttons, with SD card shield. Press button to start recoding to memory, press button again to stop recording. Program buttons to pick up one of recorded already sequences, and replay them using IR emitting diode.

 

Edited September 29, 2018 by Sensei

[Klaynos]

1 hour ago, Sensei said:

Interesting and easy project for Arduino. IR diode with serial class used to get data on the computer.

#include <Serial.h>
static const int pinIR = A0; // let it be at analog pin...
void setup() {
   pinMode( pinIR , INPUT );
   Serial.begin( 9600 );
}

void loop() {
  int state = analogRead( pinIR );
  Serial.println( state );
}

Then use Tools > Serial Plotter to see what has been received on graph. Press the all TV remote controller buttons one by one.

If the above code will work, the next step could be LCD screen shield with buttons, with SD card shield. Press button to start recoding to memory, press button again to stop recording. Program buttons to pick up one of recorded already sequences, and replay them using IR emitting diode.

 

That's pretty much exactly what I was thinking. Arduino is great for things like this. With esp8266 and ittt you can make an Alexa controlled remote (other home automation services exist).