How does this remote extender work?

This is an infrared remote control wireless extender -- it allows you to use your TV remote from a different room (no line of sight).

Most devices in this class works by having an infrared receiver sitting in the room where you use the remote, transmit the signal wirelessly to an infrared transmitter sitting in the room where the TV (or other device, like a DVR) is.

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What is unusual about this one is that it does NOT have an infrared receiver. The only interface it has with the remote control is a combination battery/transmitter that sits in your remote control (substitute as one battery).

I bought one and it actually works.

How does it know what infrared code is being transmitted by the remote, without an infrared receiver?

I can only think of two ways: (1) it monitors the fluctuation in the current drawn by the remote (2) it picks up the electro magnetic wave leaked from the remote

Either way, the signal it obtains are not designed to be used this way (probably full of noise) and needs to be processed to get the final infrared code.

Is this clever engineering or what?

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I think it's supposed to be like this:

You point your IR handheld remote at the 'base station'. The base station receives the IR and modulates an RF carrier. The RF is picked up by the RF receiver. The little RF receiver modulates an IR emitter. The IR emitter is stuck on the tv IR detector.

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

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D from BC

I'd guess that it's using approach 1.

The noise level in the signal it sees is probably less than you think. The IR emitter diodes are probably drawing tens of milliamperes when they're "lit up", while the rest of the circuitry in the remote runs on less than 1 mA (and quite possibly down in the microampere range) when there's no IR pulse actively being sent. Shouldn't require much de-noising at all.

Seems like an elegant solution. Certainly less cumbersome than the "IR to RF" adapters I've seen, that clamp on the front of the remote control.

Dave Platt                                    AE6EO
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Dave Platt

I believe this is the way it works -- there's usually a very large difference between the "idle" current and the "driving the LED" current of a remote, often several orders of magnitude.

I suspect that "processing" is little more than a bit of RC filtering -- most remote control codes contain wide margins regarding their timing.


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Joel Koltner

Everything I've tried is hyper-sensitive to the RF noise in a 21st Century household. So I'm looking into IR repeaters that connect to the household cable TV coax distribution system.

...Jim Thompson

| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson


** Nothing very clever about it.

The LED drive current is quite large and normally easily monitored from the battery compartment - dunno how it gets on if some RC maker adds a large filter electro after the battery and smoothes the current flow out !

..... Phil

Reply to
Phil Allison

I expect the LED current is the dominant current draw, a 50Khz low pass filter followed by a comparitor is probably all the filtering that's needed.

Reply to
Jasen Betts

as a teen I did that using a capacitor to block the LED current from the antenna sockets and and just put the 'dc' LED current on the coax.

at the source end I opened the remote and used aligator clips :)

many places have DC or low AC on their antenna cable already (for amplifiers etc) so that's not a general solution,

might have to use RF signalling in one of the ISM bands,

another option might be LIRC but that needs a lan appliance (PC etc...) at each end...

Reply to
Jasen Betts

As others have said, there's a very large current draw (100mA+) when the IR LED is on, and the idle electronics use

Reply to
Ben Jackson

That would even allow picking up the very common about 40 kHz modulation, necessary for many remotes.

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But that would add a 0.01 cents to the unit cost, so there's probably not much chance of it happening in practice.

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