Hi, I have a related question, if I may, even though what is explained above may already include the solution I need, I am not sure.

I use a Harmony Hub to send IR commands around my apartment. This generally works fine but LED lights cause interference and have changed the situation for me. In particular I have one remote receiver (DIY built from a kit) to control my old reel-to-reel tape recorder. This works fine until I turn lights on, then most commands are ignored.

As a first solution I put one of those brownish red IR lenses on the photo-IC. That solved the problem with some lights but not all. I now have the Harmony Hub and the DIY-receiver in a black bag. That works, but I find it, well, inelegant!

Since the Harmony Hub, like many IR extenders, has 2.5mm output jack to attach IR LEDs, I thought, can I use that electrical signal to control the DIY-receiver directly, bypassing its photo-IC (disconnecting it completely)?

The receiving photo-IC (https://pdf.datasheetcatalog.com/datasheets2/51/519374_1.pdf), has a V in, ground and output. Can I just connect the two-pin output of the Harmony Hub in lieu of the IC’s output and ground pins?

I am asking to see if there is a simple solution or protocol. Is the alternative to scope the photo-IC output, compare it to the signal from the 2.5mm Harmony Hub jack and make a resistor bridge to adjust the voltage, if necessary?

I would very much appreciate any help And all the best,

Ali Elam — NYC

Mod: link to old thread
https://forum.allaboutcircuits.com/...it-bypassing-the-receiver.171225/post-1530121

 

The IR LED drive signal probably includes the 38 kHz carrier, which the IR receiver will normally remove. These days a microcontroller like a PIC or Attiny should be able to demodulate that (rather than using a PLL). It's got to be easy to do that in assembler., if you can't find readymade code.

 

The IR LED drive signal probably includes the 38 kHz carrier, which the IR receiver will normally remove. These days a microcontroller like a PIC or Attiny should be able to demodulate that (rather than using a PLL). It's got to be easy to do that in assembler., if you can't find readymade code.

Looking at the schematic of the receiver, you are right. But I doubt I can handle what this will require to accomplish. I was hoping it would be easier and more straightforward, alas…

 

If you can find a sufficiently ancient IR receiver module, it may have a separate phototransistor and demodulator chip. Try feeding the LED drive waveform through a resistor voltage divider.

Or, simplest solution, why not a wired infrared LED from the Harmony Hub to the DIY-receiver?

 

Or, simplest solution, why not a wired infrared LED from the Harmony Hub to the DIY-receiver?

Yes, and I should entomb those two in a light-proof enclosure of some kind. It is surprising how sensitive this thing is — with the Harmony Hub and the receiver in a black bag, in a wood cabinet, light somehow still gets in. If my kitchen LED flood lights, some 25ft away, are on, it starts misbehaving — some commands work, others not. Thank you.

 

If you can find a sufficiently ancient IR receiver module, it may have a separate phototransistor and demodulator chip. Try feeding the LED drive waveform through a resistor voltage divider.

In that case, I only need the demodulator, right? That sounds more “elegant.” I can probably extract one from an old gadget with IR remote.