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how to modulate IR signal for TX ?

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123jack

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i have a series of pulses i encoded in RC5 standard on my
gpio pin 2

but i don't understand how to do the 38Khz modulation of them
can someone explain please?

jack
 

Hi,

Would help if you said what chip and what language you are using.

If you have done any code post it so we can see where you are going wrong.
 

sorry more information

I am using C language
 

Hi

Set one I/O to output RC5 signal and another pin to output 38KHz signal

Connect them both to a logic gate like 74HC02 and connect the out put of the gate to the IR LED driver (NPN or mosfet)

All the best

Bobi
 

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    123jack

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There are multiple ways to combine the 2 signals. The best (to me) is you run a pin at your desired carrier, and change its status as per your data (output when you want the bursts, input when you dont). Gives you the best output w/o any extra hardware.

Or, keep a pin continuosly outputting the carrier, and spit out the data on another. Connect your IR LED between these pins. You might not get the best range with this method.

Gate the above 2 signals to drive a transistor, which in turn drives the IR LED.

Regards,

Anand Dhuru
 

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    123jack

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Thank you for the replies.
It seems I did understnd - I just couldn't
get my head round it !

I like the carrier on/off cycle best if I can make it work
in my application - I've been trying to modulate via a FET
but if I can do away with a component that has to be worth a go.
 

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