Re: Could you suggest a good IR blaster

On 10/02/17 11:31, Maxim Levitsky wrote:
> I have an HDMI switch which comes with IR port (3.5mm jack), dongle, and 
> remote to control it.
> I want to control it from the PC.
> 
> One option is to control it by connecting it to a sound card, but I 
> measured that the switch puts
> 3.3V on that jack so I am afraid to break the sound card.
> That voltage seems to drop to almost 0 when the dongle receives the IR 
> signal.

If I understand you correctly, you would prefer to just draw a cable 
from the PC to the 3.5mm jack of the switch, but are afraid of 
connecting things that should not be connected? I am not 100% sure 
(exactly what is your "dongle"?), but you should be able to achieve this 
with an opto-coupler, like 4N28. I _think_ you can just connect pin2 to 
PC ground, pin 1 to PC signal (put a 1k resistor in between, to be 
safe), pin 4 to switcher ground (3.5mm barrel), pin5 to 3.5mm tip. But 
find out exactly how the jack is wired to be safe. Can you tell us more 
about the "dongle"? Perhaps it is even demodulating? (In which case the 
previous is garbage...) Photo?

> Other option is just to buy an IR blaster - but I somewhat don't find a 
> good one, so asking here for a suggestions. I probably can do something 
> DIY (never tried it), but would still have to be USB connected, so I 
> wonder if this is worth it.
> (Don't know how hard is to create sound card based IR blaster, and how 
> hard is to make pulseaudio to not touch the output port of the sound 
> card in this case)

You need something that generates the modulated signal in both cases, 
regardless if you are using an opto coupler or an IR transmitter. The 
Iguana that Alec recommended contains one (or two) output jacks, that 
can be used with a opto coupler. If you are capable of building stuff, 
consider http://www.harctoolbox.org/arduino_nano.html.

Greetz,

Bengt

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