Demux with infrared emitters

Hello:

I need to use four ir emitters for different devices, the problem with Arduino is that I have onley one IR output with pin number 3.
Can you tell me what demux do I need and how to active the input and outputs? Or anyway to do this?

Many thanks

Can you explain what you're trying to do, and what your limitations are, please?

amjlopez:
I need to use four IR emitters for different devices, the problem with Arduino is that I have only one IR output with pin number 3.

Then you clearly need to find three more.

That was an absurd statement. If you give complete details instead of exhibiting the "XY problem", then further useful suggestions can be made.

Well, is very easy what I want to do:

I have four devices:
1 TV
1 DVD player
1 Hi-FI music sound
1 TDT

When I use IRemote library for sending IR commands from Arduino UNO, this one use only pin 3, how can I send with other pins to other devices? or can you suggest me another way to do it.
Many thanks

I still don't see having a single pin as a limitation.
The different devices may use a different serial IR protocols, but a single emitter can usually cope with them all.

And these four devices are in different rooms?

Or do you imagine the separate remotes for each use different types of IR emitters?

(I'll give you a hint - they don't! :grinning: )

Even if they're in different rooms, you'll just need a buffer to drive multiple emitters.

And just in case - you need to know that you need a buffer in any case - you cannot drive your IR LEDs directly from the Arduino pin.

The devices are in differents rooms. Protocol for my devices are: NEC, RC5 and Sony.

How Do I connect four IR emitters to Arduino Uno and send commands to each one? I don't know how to use Buffer for sending commands.

Is possible to have any IC where you in the IR pin (in the case of IRemote library pin 3) and have multiples output and select which output to drive?

many thanks.

Is possible to do this? do you know what IC does it? (jpg is attached)
thanks

possible-IC.jpg

That was my point. As AWOL pointed out, you can send the same commands to all at once - whichever device corresponds to the particular command protocol will respond (only) to it - exactly as now happens when you choose which remote to pick up. Your only problem could be if you have the same model of device in two different rooms.

Now you do require a buffer, which is to say a logic level FET which the Arduino output can control to pulse all of your IR emitters (simultaneously). You probably want to connect all the IR emitters in series and operate them from a 12 V power supply (which would power at least four IR LEDs in series). Here is the circuit for a constant-current buffer using transistors (limited to 100 mA maximum; you actually want a different one or a FET), others may make other suggestions.

I don't need to send commands simultaneously but one after another.
Is there not a IC that do that?

MAny thanks

amjlopez:
I don't need to send commands simultaneously but one after another.

That's fine. As I said - you send the same command to all at once. Only the device that needs to respond to the command will do so. You send commands to different devices whenever you need to, but each command is sent to all IR LEDs.

This is precisely what happens when you pick up a remote control. It is sending the command to all the devices in the room. But only the device whose protocol matches the remote, responds.

Manufacturers must, even with the same protocol, distinguish commands sent to a TV from those sent to a DVD player, because they expect the two appliances to be used together, in the same room, exposed to the same remote controls. And if they also manufacture a HiFi and whatever a "TDT" happens to be, then they would want you to buy those to use in the same room also, so they must by definition, make them all respond only to the correct commands.

Then, can you tell me how is the circuit for the four IR emitters from the Arduino?
many thanks.

I gave you one version.

OK, you probably need a heftier transistor on the right such as a BD135 (BD137, BD139) and the 3k3 resistor should then be 330 Ohms as for most IR LEDs, you want to set the current (note the formula given for the resistor) to 100 mA (so, 6.8 Ohms). The "LED supply" is 12V (or could be more, does not need to be strictly regulated) and you can then put four IR LEDs in series where the LED is shown.

Note you must be careful to make sure in the code, that the LEDs can never remain switched on.

Hello:
I dont understand to much about electronic circuit. Do I have to put 8 transistor, two for each IR emitter?
Please, can you draw me a simple circuit with four IR's with Arduino.
Thank you very much.

Do I have to put 8 transistor, two for each IR emitter?

Yes.

I was hoping someone would explain what "put four IR LEDs in series" means. :roll_eyes:

Because at this moment, I really can't. Stomach it, that is.

Oh wait, Wikipedia!

Well you can put them in series but only if you have enough voltage to drive 4 times the Vforward, and you can cope with the Christmas tree effect of when one LED being not connected it makes all the others not work as well.

Grumpy_Mike:
Well you can put them in series but only if you have enough voltage to drive 4 times the Vforward

Which would be what I carefully explained and repeated in multiple posts, wouldn’t it? :roll_eyes: