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How do these IR receivers work internally ?

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MathWizard:
I'm making a remote control, for a stereo that has a motorized volume control (but never had a remote it seems).

And I'm trying some TSOP-1156 IR receiver modules, and I see that you have to have special timings to do anything. So I'll have to try it with an MCU. And I see the block diagram, but how do they do all that, and make it any good ?? Is it all digital circuits and timer's, and is there some really special purpose MCU in there ??

I'm also playing around in LTSpice with making an RF remote, with BJT's, and Colpitts oscilators, for 2 different frequencies for volume up/down. And just with the basic circuits I'm trying, I'll probably want quite a frequency separation, like 3MHz and 30Mhz, just to get 2 nicely separated voltage levels.

Kim Christensen:
Look into the RECS-80 protocol mentioned in the datasheet or others. It explains how this is typically done with IR remotes.

moffy:

--- Quote from: MathWizard on May 27, 2024, 01:00:44 am ---I'm making a remote control, for a stereo that has a motorized volume control (but never had a remote it seems).

And I'm trying some TSOP-1156 IR receiver modules, and I see that you have to have special timings to do anything. So I'll have to try it with an MCU. And I see the block diagram, but how do they do all that, and make it any good ?? Is it all digital circuits and timer's, and is there some really special purpose MCU in there ??


--- End quote ---

It looks to be straight analog, just amplitude modulation/on/off keying of a carrier frequency.

soldar:
I have played with these in the past. Be aware that they are designed for a certain carrier frequency (38 Khz?) so you have to stick to that. The receiver demodulates the signal from the carrier so you have a clean signal at the output.

If all you need is two codes, up/down, then it should be extremely easy to do with just a little hardware, no need for MCU. I can think of several simple ways. By signal duty cycle, by signal frequency, etc. If you want something more complex then an MCU is the way to go. In that case you could use a remote sender from any other device. Note that the codes they send are complex. My TV remote sends 27 bits.

I have a crate full of old remote controls and of devices with receivers waiting for projects to use them in. :)

As an

soldar:
Another thought to make it as simple as possible is to have a single signal, only on/off, and the receiver toggles each time up / down / up / down. You can have LEDs of different colors to show if it is going up or down. If you send and the receiver is going in the opposite direction to what you want you just stop and push again.

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