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Old 5th July 2006, 11:28 PM   #1
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Default 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)?
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Old 6th July 2006, 02:10 AM   #2
banana is offline banana  Hong Kong
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D flip-flop
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Old 6th July 2006, 09:38 AM   #3
seoman is offline seoman  Netherlands
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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
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Old 6th July 2006, 03:45 PM   #4
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Thank you very much!
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Old 7th July 2006, 01:13 PM   #5
macboy is offline macboy  Canada
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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.
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Old 7th July 2006, 09:14 PM   #6
gmarsh is offline gmarsh  Canada
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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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