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-   -   Adding a 38kHz carrier to IR (http://www.diyaudio.com/forums/digital-source/82670-adding-38khz-carrier-ir.html)

rtarbell 5th July 2006 11:28 PM

Adding a 38kHz carrier to IR
 
For an infrared remote controller, does someone have a quick and dirty circuit to add a 38kHz carrier to a digital signal (such that a digital "1" transmits the carrier, and a digital "0" transmits nothing)?

banana 6th July 2006 02:10 AM

D flip-flop ;)

seoman 6th July 2006 09:38 AM

2 Attachment(s)
I think this would do the trick

Make sure that you either use a darlington transistor with normal diodes or a normal transistor with schottkey diodes.

Regards, simon

rtarbell 6th July 2006 03:45 PM

Thank you very much!

macboy 7th July 2006 01:13 PM

That solution requries that the carrier be supplied separately, which is great if the carrier is already available. One trick to both generate the carrier and modulate it is to use a 555 timer, configured to output 38 kHz with 50% duty cycle, and use its reset pin to modulate the carrier with the digital signal. When reset is asserted, the 555 stops oscillating, and when it is deasserted, it starts again. The output of the 555 is sent to the IR leds, and since the 555 has high drive current you can usually drive them directly.

gmarsh 7th July 2006 09:14 PM

Quote:

Originally posted by macboy
That solution requries that the carrier be supplied separately, which is great if the carrier is already available. One trick to both generate the carrier and modulate it is to use a 555 timer, configured to output 38 kHz with 50% duty cycle, and use its reset pin to modulate the carrier with the digital signal. When reset is asserted, the 555 stops oscillating, and when it is deasserted, it starts again. The output of the 555 is sent to the IR leds, and since the 555 has high drive current you can usually drive them directly.
What he said; I've done exactly this trick in the past.

Though in a 3.3V or 5V land, use a TLC555 timer instead of a NE555.


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