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I have a pair of LED IR emitters like the ones shown below

IR LED

I have connected them to my PCs audio jack but the IR is not turning on.

Is there any way I can get them to continuously emit for a head tracking application?

BlockMan
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  • The Ir LEDs will only turn on during the Positive half-cycle and only when the positive half-cycle of your audio signal is more than the forward voltage of your IR-LED. The longer the wavelength your LEd is, the lower the forward voltage (typically is, there are exceptions). You'll need some circuitry to add an offset voltage and, well, I'm not exactly sure what you are trying to do, you'll need to post more of an explanation. – GT Electronics Jan 13 '22 at 20:16
  • Why do you think the LEDs will turn on when connected to audio output jack? Please note that connecting a mono plug will directly short the right output channel to ground, which is, of course, not recommended. Even if you played audio, say a 1 kHz square wave on the left audio channel only because right is short circuited, it would still blink at 1 kHz, and the audio output most likely has a DC blocking capacitor which gets charged on the positive half-wave and with nothing to discharge during the negative half-wave so the effect would be quite useless. – Justme Jan 13 '22 at 20:28
  • I am trying to create a head tracking device using a PS3 Eye camera which can detect IR light. I thought maybe these IR emitters as part of an IR extension kit might have worked well but I was not sure. – BlockMan Jan 13 '22 at 20:33
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    It's a 3.5 mm plug, but not a 3.5 mm *audio* plug. For each one, you need a 3.5 mm jack, a battery, and a resistor. If the tiny blue part at the lower right of your image contains some technical data, enlarge it and add it to your question. – Theodore Jan 13 '22 at 22:14

1 Answers1

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The thing you have is called an IR Blaster. The 3.5mm jack was adopted by some set-top box (STB) manufacturers as a standard for connecting Blasters to forward control codes to other gear, like TVs and home theater amps. This allows integrated control of the A/V system via the single STB remote. HDMI CEC has made IR Blaster largely obsolete, but this kludge still shows up from time to time.

What's in an IR Blaster, anyway? Usually, just a pair of IR LEDs wired back-to-back across tip and ring. This means that they can use a + or - drive.

The STB drives these LEDs with a digital LED driver signal, not an audio signal. Hacks exist to use audio for that, but this doesn't work so well with line-out audio as its current is limited. This can be overcome with a buffer. (Related: Driving LEDs from audio signal) Also, the headphone driver may give a better result.

hacktastical
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  • So is there any software which can emulate these IR signals via the 3.5mm jack or via USB (using an adapter)? I would like these IR blasters to continuously be on rather than sending coded signals on a button press, as would be the case of connected to an IR receiver device. – BlockMan Jan 14 '22 at 18:13