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I can't seem to get the op265AB infrared LED from OPTEK to light up. I'm using my phone's camera to look for light. This works with Radio Shack part 276-0142 but the OP265AB just isn't lighting up.

I've tried with 100 and 220 ohm resistors, and with 3.5V, 5V and 9V power supplies. Normal LEDs work at the same spot, as does the Radio Shack part.

The docs say that it is 850nm wavelength.

My hope is to use this as part of a model train detector.

What could I be doing wrong?

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  • \$\begingroup\$ Have you tried reversing the polarity of the diode? By the way, what's a "vlt"? Can you verify that the diode is drawing any current with a meter? \$\endgroup\$
    – Joe Hass
    Commented Mar 16, 2014 at 0:57
  • \$\begingroup\$ @JoeHass don;t be dense, you know what "vlt" is supposed to mean... \$\endgroup\$
    – Passerby
    Commented Mar 16, 2014 at 1:04
  • \$\begingroup\$ A lot of phones have an infrared filter and depending how good it is you might not see much. After checking it's drawing current you might be best to skip forward to trying the infrared photodetector or whatever you eventually hoped to detect it with. \$\endgroup\$
    – PeterJ
    Commented Mar 16, 2014 at 1:22
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    \$\begingroup\$ What order did you try your voltage & resistor combinations in? 9 V with 100 ohms gives about 72 mA, well above the maximum rating of your LED. If you tried that first, you may have blown the diode before you got a chance to try anything else. \$\endgroup\$
    – The Photon
    Commented Mar 16, 2014 at 1:33
  • \$\begingroup\$ Use a ir phototransistor. A lot more receptive. If you can't sense it like that, it's dead. \$\endgroup\$
    – Passerby
    Commented Mar 16, 2014 at 1:52

2 Answers 2

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I can't see an IR remote LED on my iPhone, so I'm not sure the phone camera means much.

If the LED has current going through it (measure the voltage across the series resistor) and the voltage across it is normal, it's virtually surely emitting light.

If the voltage across the LED is significantly less than expected for the current, the LED is fried. Some LEDs have more than one "fried" mode (sort of like medium-rare and well-done).

If the LED is drawing no current and thus has the supply voltage across it, it's either been severely damaged or is connected backwards. Curve from the datasheet here:

enter image description here

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850nm is usually beyond or below the range that the eye can perceive. Having said that, I've powered 850nm devices and seen a faint glow.

It's infra red you are dealing with so ask yourself, can you tell if your oven is on by looking at it?

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    \$\begingroup\$ The question says, "I'm using my phone's camera to look for light". This should work for most phones and most 850 nm LEDs. \$\endgroup\$
    – The Photon
    Commented Mar 16, 2014 at 1:30
  • \$\begingroup\$ @thephoton I've got an android phone and it doesn't pick up 850nm from a VCSEL. I tried it about a year ago and was surprised by this. \$\endgroup\$
    – Andy aka
    Commented Mar 16, 2014 at 1:40
  • \$\begingroup\$ Also have a Android phone, and I can see my tv remotes and stove coils and toaster oven. As I can with some other cameras like my Canon A series. \$\endgroup\$
    – Passerby
    Commented Mar 16, 2014 at 1:54
  • \$\begingroup\$ @Andyaka I have an HTC Desire phone whose camera can barely detect an IR LED's light, and a Motorola Defy phone which sees the same IR output very clearly. In neither case am I expecting to see the IR by naked eye. \$\endgroup\$
    – Anindo Ghosh
    Commented Mar 16, 2014 at 3:55
  • \$\begingroup\$ OP said he is able to see a different IR LED with his phone camera. Checking the specs of that part, it has a peak wavelength at 950 nm. \$\endgroup\$
    – The Photon
    Commented Mar 16, 2014 at 5:24

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