2013-01-30 IR Remote Emulator Learns and Sends

I’ve thought about this a number of times in the recent past.  There used to be a .ZIP file on the ‘netcalled Xanadu Zapper which consisted of plans and code to implement an IR xmit/recv interface for the PC along with code for learning and sending the IR codes.  Many years ago I built the interface (just a IR LED connected the the parallel printer port) but my TV was an old one with a weird remote so it would not work.

I decided that I would try another trick many years ago.  Since my TV’s remote was weird, I decided that the remote extender project that I had found would not work.  This project used a Sharp GP1U52X IR receiver to receive and demodulate the remote’s pulses, and then retransmit it again, I think it used a 555 timer chip.  I thought that why would you want to receive and demodulate the code and then go to all this  trouble to remodulate again, when all you really need to do is just receive the carrier, amplify it and then resend it again.  If I point my weird TV remote at it, it does the job, no problem whether it’s weird or not.  If I point my VCR remote at it, it does the job, no problem.  DUH!!!

So I built a preamplifier and IR LED driver and mounted it along with the IR phototransistor in another room and ran a twisted pair out to a point in front of the TV and VCR and connected the IR LED to it.  Then when I brought my remote into the other room, I had  complete control of the TV, VCR, or whatever.

Today, the remotes are good, but you can’t be in another room and point the remote anywhere with the hope that it will conttrol the TV or whatever.  I moved into a bigger place and now it’s not so practical to just run a pair of wires from one room, down the hallway, over the kitchen counter and to the TV ,VCR, DVR, etc.  I really miss my old remote extender; it made things a lot easier when I was moving from one room to the other.

I think it would be possible to implement such a device by receiving the IR remote carrier signal, amplifying it and then modulating it onto a radio frequency, which will only be transmitted briefly when the IR signal is being sent.  I would call this an extender.  There could be more than one of these extenders, each in its own room.  The receiver would be a low sensitivity receiver that is broadly tuned to the frequency so that it could receive the various extenders without problems.  Since only one frequency would need to be used, the receiver could be a TRF, or tuned radio frequency receiver.  The channel bandwidth would have to be wide enough to accommodate the remotes, which have a carrier frequency around 38 kHz.

This system would not have to be sophisticated, it would not need microcontrollers.  I was thinking that the best frequency to use would be one of the vacant TV channels in the area, such as ch. 7 or 8.  This is high enough to allow a small antenna, but low enough to be transmitted and received by common transistors.

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