I have posted this question also on arduino forum but can't get more answers there.

So basically I have an old DVD player that has an IR (infra red) receiver and I would like to automate it with a NodeMCU micro controller. I can do it the easy way: record IR receiver signal and then replay it from IR transmitter using MCU. However, I don't want to do it this way, maybe because I want a different / more difficult solution or i'm just dumb. I would like to drive the IR receiver without using IR transmitter, using some sort of direct connection from MCU to IR receiver.

What has been done so far: Original plan was to use transistor that would control the signal (make signal go LOW/HIGH with MCU, so i can simulate IR output) that the DVD player receives like this: enter image description here

However I got a lot of noise and so another user suggested that I use optocoupler like this: enter image description here And I still got noise, I was suggested that MCU probably can't output enough miliamps (MCU gave 10mA) to optocoupler (max operating with 60mA) so I changed the scheme to use external power that controls the optocoupler: enter image description here Credits to 6v6gt from forum.arduino.cc

Heres the latest result im at using transistor together with optocoupler: enter image description here You can see that it sort of looks like IR NEC protocol. This now ALMOST gives what I wish to achieve, but still has a lot of noise. I don't have the right equipment or knowledge to understand what is causing it and would really appreciate suggestions and help. Thank you for reading this.


1 Answer 1


You are trying to overpower the IR receiver's logic level output.

You might add a resistor in series with that "high" level, then use your transistor/ optoisolator to superimpose your data stream

  • \$\begingroup\$ In general, IR receiver modules tend to have open-drain output. But it is a good idea to check if it happens to be push-pull output. Also the voltage level at the data pin may be too low for the logic analyser to detect it properly or the logic analyser input impedance may be too low compared to data pin pull-up, so verification with real oscilloscope should reveal if those noise spikes are real or not. \$\endgroup\$
    – Justme
    Feb 23, 2020 at 22:29

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