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Rhye
Joined: 23 Feb 2018 Posts: 1
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Link Posted: Mon Feb 26, 2018 7:25 am Post subject: Why does the "generated" signal fail to work? |
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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 ?
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barclay66
Joined: 27 Jun 2011 Posts: 1291 Location: Germany
TV/Projector: Marquee 9500 Ultra
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Link Posted: Mon Feb 26, 2018 10:28 am Post subject: |
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Hi,
The series resistor to the tranistor's base should be much lower, between 1K to 4.7K. Otherwise, the transistor isn't switched off reliably when the arduino's output goes low...
Check this out: http://forum.arduino.cc/index.php?topic=147852.0
Regards,
barclay66
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