Infrared sensor

  • If you where ever wondering!

  • I normally put a shield around the IR LED using either heatshink tubing or something circular (like a short length of brass tubing).

    This helps to reduce sideways leakage and also allows you to narrow the angle of IR ligh leaving the LED (by extending the tube beyond the end of the LED).

    Using a modulated signal on the IR LED also helps to reduce false detection of ambient IR light (from the SUN or other sources).

    This particular setup is quite common on robots, and there are sensors available which have the IR LED and sensor mounted in the same package with a fixed focus. These are extremely useful for doing things like line following robots.

    And a tip for detecting IR light. Many digital cameras don’t have an IR filter and thus you can look at an IR LED using your camera and see the IR light in the view finder even though you can’t see it with your naked eye.

    I also typically wire a visible LED in series (or parallel for lower voltages) with the IR LED to act as a visual indicator that the IR LED is on.

  • Classroom

    @dhylands, I think basically all digital cameras come equipped with IR and UV filters that are directly mounted on top of the CMOS sensor. I have tried to do some UV/IR photographic projects that would have required modifying the camera sensors to remove filters, but didn’t have any cameras I was willing to hack. If it is a DSLR I can see how IR would be visible in the viewfinder, as the filter would be bypassed with the mirror down. When you went to capture the image though, it would likely be much closer to what you observe with the naked eye.

    Does anyone know if this is basically how laser rangefinders work, or how hard it would be to build one if so?

  • @kile I just tested my TV remote (whose IR is invisible to the naked eye), and on my Nexus 5, my Canon PowerShot SD790 (a non-DSLR), my Canon Rebel T5i (in video mode - since it is a DLSR), the builtin webcam on my laptop, and my Logitech C910 webcam, and I could see the LED firing on all of those.

    My iPad Mini seems to have an IR filter (I couldn’t see it there).

  • Classroom

    @dhylands very interesting! My experimentation was much more oriented to UV (“invisible” patterns on birds, flowers, etc), which is much more of a problem to photographers than IR, but I remember reading the on sensor filters were both IR/UV. My guess is the shorter wavelength IR, which is closer to visible light (and is therefore more problematic to photographs) is probably being filtered, and the IR in your remote may be a longer wavelength? I’m not sure if there is a standard wavelength for IR in electronics, but I do know you can buy LEDs in many UV bands (IR is probably the same). This is good to know, thanks for running for experiment!

  • I think most apple products have a filter. I found this out last year.

  • IR a closer look.

  • AGE OF ELECTRIC - Remote Control

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