Logitech Harmony Hub - IR to RF to IR

I have a Logitech Harmony hub that has 2.5mm connector to attach an IR blaster. The issue is that the IR blaster needs to be in a different room relatively far away. So my idea is:

  1. Harmony Hub 2.5mm output to Arduino
  2. Arduino "monitors" the signal from the 2.5mm output and sends it out over RF
  3. Another Arduino has an RF receiver that then converts that back to what the Harmony Hub sends. The Arduino then drives an IR transmitter connected to it.

Reading other posts it seems the Harmony Hub sends out a modulated signal. Looking at that signal, it seems it usually goes high for about 15us and then goes low for 10us. So one idea is that I simply sample that signal from the hub and send one command over RF when it goes from low to high and send another command when the signal goes from high to low. The other Arduino receives that signal and then drives a pin, with an IR transmitter connected, low or high. That would be kind of the dumb way, i.e. the Arduino really doesn't care about codes and just tries to mimic the analog signal that comes out of the Harmony Hub. Could this possibly work or is that analog signal from the hub too unreliable?

It might be more robust if the Arduino actually can decode the (modulated) signal from the hub to get back a 'pure digital' signal. Then the Arduino transmits that signal over RF. On the other side the other Arduino decodes the RF signal, modulates this signal for IR and drives an attached IR transmitter.

What approach is better? If it's the decoding/encoding one (the later one), then how do I decode/encode the signal?

You should be sure whether the signal is analog or digital. The 25┬Ás indicate a carrier frequency of about 40kHz, used with most IR remote controls. In this case the IRremote library will do most of the job, at both the sender and receiver side.

For simplicity you can fit the signal directly into a dumb RF sender, and the received signal to an amplifier and IR LED.

Hmm, so that would leave the Arduino out completely. Basically, that the output from the hub, connect it directly so an RF transmitter (which will need a small power supply). Then on the other side I just have the receiver, power supply for the receiver, a transistor to drive the IR LED and I am done.

If that works this would be super simple. Thanks for pointing this out. I am waiting for my IR LEDs and will give this a try.

Run a long cable first and see if it works. Really seems like the most sensible thing to try before jumping into a mess.

What puzzles me is the nature of the device, normally connected to the 2.5mm jack. Is it an IR LED, or a circuit with its own power supply? This can yield different results, depending on the chosen line termination. So yes, a short cable instead of the wireless transmission modules will allow to check for proper signal conditioning at the input (transmitter) side, and for LED driver and power supply at the output (receiver) side. But a long cable might introduce its own problems, which don't exist in RF transmission.

Ah, good point about a long cable. In our old home I did pull wires through walls/floors, across the crawl space and back up the floor/wall. I was thinking of doing the same again but in our new home it's not so easy. However, your post just made me think of a different solution. I have power and Ethernet cables going to each window for shades. We just decided that we will go with wireless blinds so now I can use that Ethernet cable for other things... like an IR transmitter. I think it's about 60-70' of Ethernet cable for the room I have in mind.

DrDiettrich mentioned possible concerns about long wire lengths. I think 60-70' of Ethernet cable (23AWG, twisted pair, not shielded) should be ok. So I guess I could just hook up the Ethernet cable to the hub with a 2.5mm connector and on the other side attach an IR LED. That would be very simple.

I did take some x-ray images of the IR blaster that Logitech provides. It seems that the IR blaster simply consists of 3 IR LEDs with transistors. I am not sure if the multiple LEDs are for covering a wider range and/or different frequencies.