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Surfing the web, I found a
very interesting (now discontinued) IR universal remote device: the Total
Remote made by Griffin. This device was used with a Windows Pocket PC and
consist of an IR transmitter designed to be put in the headphones connector
and a Windows Pocket PC program to capture, learn and re-transmit the IR
signals. But how did they do it?
The IR signals are saved as a stereo audio .wav files with two half
frequency sine waves out of phase by 180 degrees (one in each channel). In
the transmitter each channel are connected to an IR led in such a way so
that when the sine wave peaked it would emit a short IR pulse. The result is
an IR carrier at twice the max frequency of an audio player (~22 kHz),
thanks to oPossum for this explanation :-).
Check out our interpretation (the IR sampler) of oPossum's circuit and PIC
software below, (click on the picture to enlarge it):
| The empty IR
sampler pcb. The device is based on a PIC 12F675. The schematic is
included in the pcb zip file archive. |
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PCB file updated
2010.04.28. |
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The IR sampler pcb with all the components mounted. |
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The IR transmitter. I have attached a
2 pin female molex to left and right inside the 3,5mm jack from Neutrik,
soldered two IR diodes together and they fit very nice into the molex
connector. |
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File updated 2010.05.09 |
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A look inside the finished IR sampler box (a Bopla E-420). |
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The front of the finished IR sampler box. Place your IR remote approx 5
cm from the IR diode (yes it works as a receiver) and press the IR
remote botton you
want to analyze or record. |
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The backside of the finished IR sampler box. The device will run fine on
an AC/DC 7-15 Volt wall outlet or a 9 Volt battery (remember a diode eg
1N4007 if you want to use an AC wall outlet). Connect the 3,5 mm
output jack to your computer microphone input connector to analyze or
record the IR signal. |
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This is a screendump from the Goldwave audio editor, my brother has used
to record the IR signal in 48kHz, 16 bit .wav format. |
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Before transfering the recorded the IR signal to eg an iTunes playlist
(eg TV), you need to normalize the audio. |
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This page was last updated
2010-05-09.
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