IR Removal of carrier

[mitchjs]

Hi all,

I got a little project im attempting, i want to make something that is IR, RF.

I can only modify the circuit at the ir LEDS and IR RECEIVER

the receiver is easy...

how at the LEDS of the transmitter, can i take the 40khz modulated signal, and remove the the carrier, so i can get it back to logic and
connect it to my rf transmitter

thanks
mitch

 

[ThermalRunaway]

From what I understand of your post, you've got an IR remote control type signal and you want to demodulate it to obtain the digital information so that you can re-transmit it via RF.

In order to demodulate the signal you need to dispose of the 40Khz carrier, but before you do this you need to design an AGC stage so that the signal provided to the the demod circuit is of the correct level. Most IR Remote protocols have information contained within the transmission (the leading pulse) which set the level for the AGC. Once the level of the incomming signal has been set properly you can strip away the 40Khz signal which leaves you with the original digital information. To do this you need to design a suitable filter circuit to take away the 40Khz carrier.

If all that sounds like way too much work, you could always use one of the "ready made" components out there which will do all of the work for you. You can get IR Remote ICs which allow you to feed in the 40Khz carrier signal and they will feed out the digital information, and you can even get packages which make up the receiving IR Diode, the AGC stage and demod circuit all in one go! The Sharp GP1U52X is an example of this. With this device you can receive the IR Remote signal and the device will feed out the digital information for you, so there's no need to be designing anything yourself in that respect.

Hope this is of use.

By the way, hi everyone - this is my first post.

Brian

 

[mitchjs]

YES, thats what i want to do

I want to not do it optically

I want to remove the LEDs and connect their drive to some IC
that will strip the carrier off, so i can send it to a RF transmitter
LYNX device

where do i find one of the "ready Made" remote ICs?

mitch

 

[ThermalRunaway]

Well that Sharp device I told you about will do what you want. It's an IR receiver, AGC module and demodulator all in one package. I've never used that component but I assume it's readily available from electronics suppliers?

If not I'm sure I can do a search and find an equiavalent IC that'll do a similar job, but try to get that Sharp part first because that really is an ideal solution

Brian

 

[mitchjs]

thats a OPTICAL solution

i cant use that

i need to remove the LEDs

mitch

 

[Nigel Goodwin]

thats a OPTICAL solution

i cant use that

i need to remove the LEDs

mitch

It would be a LOT easier to do it optically, as already suggested the devices to do so are commonly and cheaply available.

Otherwise you might try an NE567 tone detector PLL IC, tune it to 40KHz, and use the detector output for the recovered data.

You should be aware that BOTH methods don't produce exactly the same data that was transmitted! - this is why radio and IR data links don't use standard RS232 type techniques.