How to use the Infra Red LED's with Pi NOIR camera V2?

Question

I was looking at a project in which it tells to use the Pi NOIR camera along with Infrared LED's. It says that night vision will be better if we use IR LED's with the PiNOIR camera. But how to connect them?

Answer 1

It's an interesting question. Try to keep track of the wavelength of the IR LEDs you use. You might see numbers in the range of 780 nm to 940 nm (or outside as well). The shorter wavelengths will be slightly visible even in cameras with IR filters (that deep red light you see in some IR lights for security cameras) whereas the longer wavelength ones won't show up at all, and even without the IR filter your camera (any thin silicon detector will be somewhat less sensitive.

Also remember at night that if your only light source is your LED(s) then things twice as far away will be illuminated only a quarter as brightly, so a really bright LED that's far away might give you better uniformity over a range of depths than a weaker LED that's closer to your closest object.

The way to connect IR LEDs is first to know the current they are rated for, and then provide a current source that won't overload them or burn them out exactly the way you would connect a visible light LED. This site and the internet in general will be filled with explanations how to hook up visible LEDs, you can use a passive resistor or something more fancy.

I'd do it like this:

1. get a bright visible light LED. Note the maximum safe current in the data sheet.
2. learn how to power your visible LED without burning it out.
3. turn out the lights.
4. use a normal Pi camera or a Pi NoIR (it doesn't matter) and illuminate the scene with your visible LED and learn how to get acceptable illumination.
5. get a bright IR LED
6. lather, rinse, repeat. (i.e. go through the same steps with this LED.)

SAFETY NOTICE: While I am not very knowledgable of the subject, @OyaMistAeroponics's comment is really worth taking note of, and links to a very helpful discussion of the problem with bright infrared light. Take some time to read it!

https://www.intersil.com/content/dam/Intersil/documents/an17/an1737.pdf

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Here is a random sensitivity curve from the internet: https://www.raspberrypi.org/forums/viewtopic.php?t=63115#p529980

Every sensor is different, but most will look a little like this. The wiggles are due to thin-film interference from coatings on the sensor, and the drop at long wavelength is cause by a combination of limited absorption at longer wavelengths (silicon becomes more transparent closer to the band gap) as well as recombination.