Adding a 38kHz carrier to IR

[rtarbell]

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]

D flip-flop

[seoman]

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]

Thank you very much!

[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.

[gmarsh]

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.