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Topic: Measuring the intensity of fog using a light source, pixy cam, Arduino (Read 1 time) previous topic - next topic

saa0d

Please realize that to someone who DOES understand photodiodes and how they are used, this argument is complete nonsense:

When asking for advice on a technical forum, do some research and thinking before responding, otherwise people will assume that you are an idiot and and a waste of time.
I don't know if I'm not asking my question properly or not. For the case of a photodiode, I need to have a beam of light directed at my diode, which means the light and the diode should be stationary. My drone flies over a number of light sources, and they are not directed at the drone, like the lights available on a runway! That is why I'm asking how to do it with a camera, not a photodiode. Because, I know how does a photodiode work, and it would not do the job I need it to do!

TheMemberFormerlyKnownAsAWOL

Quote
For the case of a photodiode, I need to have a beam of light directed at my diode, which means the light and the diode should be stationary
And how is this different for a camera?
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jremington

Quote
I don't know if I'm not asking my question properly or not.
You haven't thought through the project completely, which makes it impossible to ask good questions.

It sounds like your advisor is not much help.

zoomkat

"Thus, I need to have a camera, that can focus on a single spot (LED perhaps), and from a distance. It measures the intensity of that light source and translates it into a percentage of visibility, and when the visibility drops under a certain level, the drone would start spraying the solution to dissipate fog. I'm targeting airport runways if that would give you a better idea."

Well, most large airports already have installed instruments that measure "cloud ceiling" and "visibility". You might take a look at how these work. I would assume you would have to set your remote light source as a beacon that your drone could identify, and then do its monitoring.
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saa0d

And how is this different for a camera?
The main difference I believe exists, the photodiode needs a light beam to be concentrated on it. But for the camera, the light does not need to be directed at the camera, whereas the camera will identify it as a colorful bright spot through the fog; and I need to measure the intensity of this bright spot. So to emphasize, I don't want a light like a laser directed at my camera or photodiode, I just want to measure the intensity of a (colored) bright spot, whether it's directed at the camera or not. Hope that makes things clearer

The key idea here Is that the camera should focus on the light, not the light focusing on the camera/photodiode.

TheMemberFormerlyKnownAsAWOL

Would it help if I pointed out that a CMOS camera sensor is, in essence, an array of photodiodes?
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saa0d

Would it help if I pointed out that a CMOS camera sensor is, in essence, an array of photodiodes?
That's is certainly new knowledge to me. But it remains true that the camera can identify and focus on only one light spot, and the photodiode cannot, right?

TheMemberFormerlyKnownAsAWOL

The camera will focus on whatever it is pointed at.
A lot like a photodiode with optics.
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TheMemberFormerlyKnownAsAWOL

A bit like those, yes, but, you know, with optics.
A lens.
Like on the front of a camera (unless it is a pinhole camera).
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jremington

Build your camera system and when it is working as "designed", post again.

I'll look forward to it!

Idahowalker

One could do a internet search on the words "Optical Fog Sensor."

There are, also, math formulas that can be used to derive fog density from some common measurements; such as pre-fog/during fog temperatures and humidity. But the neatest thing of all is a OFS.

jremington

Sadly, the OFS uses laser light backscattering and a photodiode, which the OP has most emphatically rejected.

TheMemberFormerlyKnownAsAWOL

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