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ailee
Starting Member

China
4 Posts

Posted - 11/08/2016 :  12:24:13 AM  Show Profile  Visit ailee's Homepage  Send ailee an AOL message  Reply with Quote
I am trying to replicate the remote control for my Sony home theater system. I started with anaylzing the demodulated signal of power on button using a TSOP1738 IR demodulator(http://www.kynix.com/Detail/840529/TSOP1738.html). It looks like this:



You can see the signal (along with the decoded command). Next I replicated the signal using the Arduino (and as per SIRC protocol, chose 1/4 duty @ 38Khz). Below is the signal of a complete one to show the code sent and a zoomed one to show the 38Khz 25% duty burst within the signal.




Now to drive an IR LED using this signal, I fed this into a 2N2222 NPN BJT transistor's base with its collector connected to +5V and base to IR LED -> Series Resistance -> GND. And to test the signal I fed this "generated" signal through the TSOP1738 again and probed the output.



The signal I get looks like an IR signal except for the 1's (when TSOP1738 goes LOW) instead of being LOW for a duration, as in the first image. I see a lot of toggling going on:



The "generated" signal, of course, does not work. Any idea what's going in here ?

BLH
Advanced Member

5603 Posts

Posted - 11/08/2016 :  05:53:46 AM  Show Profile  Reply with Quote
My thoughts are.
The decoded output data is decoded from the 38KHz IR bursts sent by the remote.
You have to use the decoded data to control a 38KHz signal generator circuit, to drive the IR LED. With the encoded data bursts.


Edited by - BLH on 11/08/2016 05:58:17 AM
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