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For all the other stupid things I often do, I've found ways to boobytrap myself. For example keeping my wallet on the floor where the door opens - I can't help but stumble on it when I leave the house. But here's an electronics parts problem that has me stumped.

I sometimes accidently throw out IR LEDs as "nonworking" since they don't visibly glow when tested. How can I prevent myself from doing that, at least to force myself to reconsider and remember there's such a thing as IR?

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Tape your trash can shut, and instead of throwing the LED away, put it in a 'TO TEST' container :-)

There is a way to test them visually:

  • get your digital camera
  • turn camera on
  • power the IR LED
  • point camera at LED
  • look at camera screen, you should see the LED lit up (if it still works)

You can find video's on Youtube about this.

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    \$\begingroup\$ Camera phones are great for this \$\endgroup\$
    – ajs410
    Nov 4 '10 at 16:13
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    \$\begingroup\$ The idea of making the trash can harder to use would prevent a lot of disasters! Though maybe lead to more of others.. \$\endgroup\$
    – DarenW
    Nov 5 '10 at 2:20
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After LEDs fail, they rarely electrically resemble diodes any more. If you have a DVM that has a diode test mode, use that. Mine shows a representative forward drop of 1.2 to 1.5V for various sorts visible LEDs (just talking reds, yellows, greens here), and 0.9 to 1.1V for IR ones.

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What Vincent mentioned above is the method I'v been using so far, and is the easiest :) just take any cam (mobile or point n shoot) and when you see the IR LED through it you should be able to see a purple color light I guess (Unless I am color blind ;) )

JUST AS A NOTE DON'T FORGET TO KEEP A RESISTOR(lower value like 220-470E) IN SERIES TO THE IR LED WHILE YOU POWER IT UP AS YOU DON'T WANT IT TO BURN UR LED :)

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  • \$\begingroup\$ The color varies by phone, what you added in all capitals makes up most of your post, which is really a comment. In just a little rep you will be able to post comments. I would suggest against all capitals in all situations. Bold if you want it to stand out. \$\endgroup\$
    – Kortuk
    Nov 5 '10 at 2:07
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    \$\begingroup\$ CAPS-LOCK: IT'S CRUISE CONTROL FOR COOL! \$\endgroup\$ Nov 5 '10 at 5:51
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Almost all digital cameras like the one in an iPhone has enough bandwidth to pick up IR. To prove this to yourself get your digital camera and look at an IR remote with it and you will see the IR LEDs. As pointed out by others expensive digital cameras sometimes put optical filters to allow only the visible range in. A fun thing to do is to use your phone camera to look at things like atms and other security devices that use the IR range to operate in.

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  • \$\begingroup\$ It is not a range issue with the phone, it is the presence of an IR filter. High quality cameras have this. \$\endgroup\$
    – Kortuk
    Nov 5 '10 at 2:08
  • \$\begingroup\$ @Kortuk you are correct about the IR filter however most webcams and digital cameras don't have the filters. My iPhone sees IR just fine. \$\endgroup\$
    – Rex Logan
    Nov 5 '10 at 2:18
  • \$\begingroup\$ I know that, I use them regularly. You stated "Almost all digital cameras like the one in an iPhone has enough range to pick up IR.". It is not a range issue. That is what I am stating. \$\endgroup\$
    – Kortuk
    Nov 5 '10 at 2:20
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    \$\begingroup\$ Unless you mean range as in percentage of the spectrum, in which case I would say no IR filter. Most people would call it bandwidth, I would at least. \$\endgroup\$
    – Kortuk
    Nov 5 '10 at 2:21
  • \$\begingroup\$ Basically all camera have IR filters, including the iPhone, webcams, etc... However, the reason they can see IR anyways is because the filter is not perfect, and IR LEDs are generally very bright. \$\endgroup\$ Nov 5 '10 at 5:49
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Funnily enough, I've solved the problem myself assuming the question didn't come up, and only then searched for it :). Although I think the camera phone approach is usually the most practical, here's the solution I applied, in case someone finds it useful:

If you have a photoresistor that's sensitive to IR, you can just connect it to a multimeter and place it in front of the LED. Obviously, if there's a change of resistance as you turn the LED on and off (without affecting ambient light sources), this means the LED is working.

Caveat: you have to have to at least have the datasheet for your photoresistor somewhere handy (and one good enough to show you wavelength sensitivity), and at least remember the highest operational wavelength of the IR LEDs you have stocked.

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You could also try using an IR filter as you would find in a camera store. Under such filter they should glow, just about enough to be visible.

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    \$\begingroup\$ IR Filters will block the IR. You actually want your camera to not have an IR filter. \$\endgroup\$
    – Kellenjb
    Nov 5 '10 at 2:11
  • \$\begingroup\$ And, they also make filters that block everything above IR. Most folks can see IR (barely) to a certain extent, making this solution perfectly valid. But yes, one of the digital camera options is probably better. \$\endgroup\$
    – Brad
    Nov 7 '10 at 21:31
  • \$\begingroup\$ Sorry - they are sometimes called IR filters. For example, you can sometimes get a red filter, which only allows red, or which blocks red. It's just terminology. \$\endgroup\$
    – Thomas O
    Nov 7 '10 at 21:51

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