I have an infrared LED as part of an IR transceiver, and I want to determine its polarity. As the device is unmarked, finding its datasheet is out of the question. And, as it is infrared, seeing it light up is also out of the question.
Using my multimeter on its diode setting, I connect the positive multimeter lead to one of the device pins, which we will call pin 1. I then connect the negative multimeter lead to the other pin (pin 2). Doing this, I measure a voltage drop of ~1.3v. I then swap the leads and measure a drop of ~0.5v. Unfortunately I do not know what to do from here, as both directions give me a reading.
Based on these readings, is it possible to determine its polarity? And if so, what IS the polarity?
Thank you for your time.
Best Answer
The direction with the lower voltage drop is likely the forward direction. The reason you get a voltage drop in the reverse direction is likely because when reverse bias, your IR emitter LED becomes a photo diode that's sensitive to same wavelength of IR. If you can get another strong IR source, shine it while it's reverse biased and see if it changes.
This is similar to this questions: IR emitter in reverse bias?