Photographic Flash Sources?

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ka7ehk
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Posted by ka7ehk: Tue. Aug 15, 2017 - 03:57 AM
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I am talking about "flash" in the optical sense, rather than the memory sense.

 

I have an application where such a device would be very useful. I think that I have seen some as small gas-discharge tubes. I would expect that there may be some LED ones out there. Does anyone have suggestions for technical information sources (optical spectrum characteristics, life time, and such) and driving circuitry and sources? I am hoping to find something with a useful spectrum that extends from near-IR to blue.

 

Yes, I know that Google Is My Friend, but I am hoping that someone will be able to fill in some background information before I start the search process.

 

Many Thanks,

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Learning and Information, General Electronics
Last Edited: Tue. Aug 15, 2017 - 03:59 AM
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meslomp
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Posted by meslomp: Tue. Aug 15, 2017 - 05:31 AM
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Jim,

 

You might have a look at strobe lights.

Recently saw one that had LED's in them it was so bright that even when writing this my eyes hurt again as I accidentally looked right into one that fired.

As the light was bright white I guess the blue was in there. as IR is more a heat source that might be a no go, but then again also LEDs emit IR light.

 

In that case you would not have to much worries on lifetime.

 

As with my knowledge on power led's (that is what you will be heading at) the ones I tested for a intelligent flashlight were current controlled, and as such needed a special controller, but they are becomming more and more common as now a days every self respecting silicon manufacturer seems to have a couple that should be able to suit your needs.

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Bronze Markawneil
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Posted by awneil: Tue. Aug 15, 2017 - 06:20 AM
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Traditionally, photographic flash units used Xenon discharge tubes - so that would be your search term.

 

Phones use LEDs these days.

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ka7ehk
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Posted by ka7ehk: Tue. Aug 15, 2017 - 06:52 AM
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Thanks!

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Brian Fairchild
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Posted by Brian Fairchild: Tue. Aug 15, 2017 - 07:21 AM
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ka7ehk wrote:

...something with a useful spectrum that extends from near-IR to blue.

 

Whilst the output from a flash tube looks 'white' the spectrum is anything but continuous, instead it has many peaks and troughs which may, or may not, be relevant in your application.

 

If this is for a one-off, or a small batch, then a good source of cheap smaller output flash units is disposable cameras.

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Posted by Goorman: Tue. Aug 15, 2017 - 07:35 AM
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Hi awneil

 

 Modern technical also uses xenon in car light that is really annoying.

 

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Bronze Markawneil
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Posted by awneil: Tue. Aug 15, 2017 - 08:14 AM
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Gas discharge headlamps are now being superseded by high-power LED technology.

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valusoft
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Posted by valusoft: Tue. Aug 15, 2017 - 08:17 AM
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I agree with the used disposable camera suggestion. Before they disappeared forever I collected a couple of dozen from the local store. They used to sell and develop the majority around the time of the local high school end of year "bust ups" (graduations). No student wants to take their expensive smartphones to such dangerous events... according to the store owner. The added bonus for me was all of those batteries with plenty of capacity remaining. If you go this path just be warning about the 80uF 330 volt electro which may still be charged. It packs a punch! How do I know?

 

Ross McKenzie, Melbourne Australia

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Posted by avrcandies: Tue. Aug 15, 2017 - 01:33 PM
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Jim:

 

Take a look on the right side under "app notes"...these guys are the real deal

 

http://www.excelitas.com/Pages/Product/Flash-Lamps.aspx

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ka7ehk
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Posted by ka7ehk: Tue. Aug 15, 2017 - 02:04 PM
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This is for a potential product, not one off. Appreciate the suggestions.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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avrcandies
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Posted by avrcandies: Tue. Aug 15, 2017 - 03:16 PM
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In case you order some parts !!!

 

On Monday, August 21, the US will view - what is for some - a once in a lifetime event: a solar eclipse.

The office of Tourism for the State of Oregon predicts Oregon will welcome over a million visitors (about 25% of our total state population) to watch the event.

 

Unfortunately, UPS® and FedEx® has advised that with so many extra people on the roads on Monday, they will be counting August 21 as a non-guaranteed ship day for our location.

We have also been advised that extensive web traffic may cause a delay in your online experience as well.
 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ka7ehk
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Posted by ka7ehk: Tue. Aug 15, 2017 - 03:26 PM
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I am very close to the mid line of totality. That is exactly what the local media has been advising. 

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Bronze Marktheusch
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Posted by theusch: Tue. Aug 15, 2017 - 04:24 PM
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ka7ehk wrote:
This is for a potential product, not one off. Appreciate the suggestions.

Put one of these into each unit:

Image result for flasher

Oh, wait -- that is a "flasher photo", you asked for a "photo flasher".

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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ka7ehk
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Posted by ka7ehk: Tue. Aug 15, 2017 - 04:28 PM
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Right, Lee!

 

Might almost create the same response, though!

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Paulvdh
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Posted by Paulvdh: Tue. Aug 15, 2017 - 04:49 PM
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3minute youtube of a french guy with a 1.6kW LED light

He claimes it generates 2000lux @4m.

I selected this video because it gives a relative good indication of how much light it produces and it also has an overview of the electronics to drive the leds.

 

https://www.youtube.com/watch?v=...

 

Some Idea's:

If you only need brief flashes you don't need all those power supply's. but you can do with a 400V capacitor and a triac / Power MOSfet.

Power LED's have a bit of aluminimum on them, which takes several seconds to warm up, So if your flashes are brief enough you don't need extra cooling.

LED's are available in lot's of different spectra.

 

Edit:

lm -> lux

(@ 2m20s into the video)

I never can keep those quantities apart.

(Tnx Brian).

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Last Edited: Wed. Aug 16, 2017 - 01:03 AM
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Brian Fairchild
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Posted by Brian Fairchild: Tue. Aug 15, 2017 - 04:53 PM
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Paulvdh wrote:

He claimes it generates 2000lm @4m.

 

And clearly doesn't understand photometric units.

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ka7ehk
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Posted by ka7ehk: Tue. Aug 15, 2017 - 05:32 PM
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My application will involve only a few (maybe 1 to 4) flashes per day. Flashes short, maybe 10-50ms if LED.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Posted by DocJC: Tue. Aug 15, 2017 - 09:15 PM
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The Xenon flash tubes are usually rated in Joules and have a life span duration.

 

You can crank out even more light by exceeding the tube's energy rating, but it will decrease the tube's life, and too much energy will explode the tube.

 

You can adjust the energy based upon the capacitance of the storage cap, and the voltage to which you charge it.

 

Classically  a Triac is/was used to trigger the primary of the transformer that generates the high voltage trigger, (used to ionize the gas and start the discharge from the energy storage cap).

 

You didn't mention your application.  Camera flash, warning light flash, etc.?

Just doing single flashes, or doing multiple flashes?

 

Know that the flash tubes also come in different shapes.

One of the nice features is their wide or Omni directional light radiation, as opposed to LEDs which often come with three different dispersion patterns, and are obviously much more directional.

 

JC

 

Edit: Typo

Last Edited: Tue. Aug 15, 2017 - 09:16 PM
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dak664
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Posted by dak664: Tue. Aug 15, 2017 - 11:34 PM
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What pulse length do you need? Flash tubes can be microseconds, An 80 lumen millisecond LED flash gives the same lumen-seconds as an 1 microsecond 80 klm flash tube. 80 lumens is considered the threshold for tactical flashlights that momentarily blind a person. Those are inexpensive and usually have a strobe mode that you could hack into.

http://www.policemag.com/channel...

 

 

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Posted by ka7ehk: Tue. Aug 15, 2017 - 11:39 PM
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Flashes are probably far enough apart - seconds to minutes - that they can be considered a series of single flashes.

 

The possible application is to measure the color of developing plants and trees. Natural illumination is too variable to get accurate measurements. A flash at night, when there is little or no other illumination, should make a big difference. Even if the source is made up of discrete emission lines, as Xenon probably is, it is the RATIO of the illumination to the response that is important. Another big plus for the flash strategy is that the color (of the light source) should be quite consistent from event to event. The ratio is figured at each color that the sensor can resolve. In my case, there are blue, green, red, and IR sensing elements. IR is a critical measure for plant growth & behavior. 

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

Last Edited: Tue. Aug 15, 2017 - 11:40 PM
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Posted by westfw: Wed. Aug 16, 2017 - 12:23 AM
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This is for a potential product, not one off. Appreciate the suggestions.

AFAIK, Xenon strobe tubes are still available on a commercial basis.  After all, they are still used in photography, emergency beacons, stop-motion timing, and "disco" lighting.  Nothing else comes close in terms of dumping out that many lumens in a millisecond or less.

 

The classic internet electronics reference is http://www.repairfaq.org/sam/str...

 

The interface to cameras is pretty standardized, and you may be better off implementing that rather than a full strobe circuit - it would permit  swapping in a wide range of different size/power/etc units, and offer much better safety features.   (maybe?  the interface used to be as simple mechanical switch.  fancy modern strobes communicate a bunch of data for time-of-exposure metering and stuff.)

 

LEDs are catching up, especially in phones.  Many of the big LED vendors offere special "flash" versions: http://www.lumileds.com/lighting...

 

In smaller quantities, various xenon strobe tubes and modules (especially those from disposable cameras) are common in the hobbyist/surplus market: http://www.goldmine-elec-product...

 

And the disposable film cameras (with xenon strobe) are still available: https://www.walmart.com/ip/Fujif...

 

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Posted by avrcandies: Wed. Aug 16, 2017 - 01:53 AM
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You can pulse some regular 20ma IR leds at several AMPS for a few microseconds (at a low duty cycle)..they just keep humming. But you need to do some testing on the specific part number if you go that route.

Used that in a product long ago to get a very high peak pulse.  In fact, I just saw one buried in my garage the other day lurking under 10 years of pileups.

 

Jim--not sure if you are delving into this area--but it is quite interesting:

Use this specially modified webcam to analyze plant health, in combination with the Infragram.org image processing tool to measure photosynthesis. Based on the same multi-spectral satellite imaging techniques used by NASA, this USB camera lets you take simultaneous infrared and visible photographs at 1600x1200 pixel resolution.

https://www.adafruit.com/product/1722

 

https://www.raspberrypi.org/blog/whats-that-blue-thing-doing-here/

 

 

 

 

 

 

 

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ka7ehk
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Posted by ka7ehk: Wed. Aug 16, 2017 - 02:15 AM
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Same basic principle but with a much, much shorter access time. For example, think of timing of activities in an apple orchard but MUCH simpler (and lower cost) than a full camera. 

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Posted by Paulvdh: Wed. Aug 16, 2017 - 02:44 PM
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How can it be much simpler & much cheaper than a bog standard cheap webcam?

Or one of those camera's with I2C interface?

 

Just curious:

Are you trying to sample / average a whole tree at once or more to analyse a hand picked single leaf?

It seems more logical to build a device in which you can put a leaf but that would not need high powered flash lights.

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Last Edited: Wed. Aug 16, 2017 - 02:58 PM
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Brian Fairchild
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Posted by Brian Fairchild: Wed. Aug 16, 2017 - 02:57 PM
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Paulvdh wrote:

How can it be much simpler & much cheaper than a bog standard cheap webcam?

 

Whilst the webcam itself might be cheap, the PC needed to talk to it is anything but.

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Posted by theusch: Wed. Aug 16, 2017 - 03:09 PM
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ka7ehk wrote:
The ratio is figured at each color that the sensor can resolve. In my case, there are blue, green, red, and IR sensing elements. IR is a critical measure for plant growth & behavior.

Sounds like fun.  We use the Taos color sensor in a couple apps; seems to work well.  But with the model I use, frequency output, one needs to count pulses for a relatively long time(say 100ms) to get a decent reading, then configure for the next "color" and repeat.  Not ideal for your "flash" scenario.

 

Anyway, when picking your light source, remember that the source(s) may be biased to a particular color, and not be "pure".  Might make "white LED" more attractive.

You can put lipstick on a pig, but it is still a pig.

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ka7ehk
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Posted by ka7ehk: Wed. Aug 16, 2017 - 03:12 PM
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My device would look at whole trees. A video camera needs major image processing to get tree-level information. Mine does not. Mine is easy to evaluate for a wide variety of conditions.  A video cam from a tower or drone, on the other hand, can "see" a large area of orchard or forest. So, while some of the functionality overlaps, some does not.

 

This is an extension of a device I built previously and was discussed on the list about a year and a half ago. It "failed" because the color of incoming light was too variable and I could not get a good measure of it throughout a day. This adaptation supplies its own light so gets around the earlier problem. One of the issues is that the light source needs to be quite broad spectrum - 1200nm to 400nm, give or take some. This is because leaf reflectivity in IR and fluorescent frequency conversion down into IR from shorter wavelengths are important attributes.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

Last Edited: Wed. Aug 16, 2017 - 03:19 PM
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Brian Fairchild
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Posted by Brian Fairchild: Wed. Aug 16, 2017 - 03:25 PM
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ka7ehk wrote:

...the light source needs to be quite broad spectrum - 1200nm to 400nm, give or take some.

 

Does the spectrum need to be continuous? Or could you get away with carefully chosen spot wavelengths?

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ka7ehk
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Posted by ka7ehk: Wed. Aug 16, 2017 - 03:30 PM
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I think that a discontinuous spectrum would work. Don't know and really need to talk to some plant physiologists (which I think I can find at the university). There MAY be some key wavelengths that would cause problems if missing (like the ones that start the chain of reactions in chlorophyl, ending up with emitted long-wavelength light). I need to find out how narrow that excitation window is.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

Last Edited: Wed. Aug 16, 2017 - 03:33 PM
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avrcandies
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Posted by avrcandies: Wed. Aug 16, 2017 - 04:52 PM
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Whilst the webcam itself might be cheap, the PC needed to talk to it is anything but

Hardly (to believe) these days...an RPi  (about $40) does a great job, plus has all kinds of vision processing software ready to use for face tracking, robot guidance, picture taking, etc.  Makes reading a 4x4 keypad seem old school indeed.    

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ka7ehk
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Posted by ka7ehk: Wed. Aug 16, 2017 - 05:07 PM
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The hardware and software for a cam is cheap. Not so easy to apply, however. Power consumption is also relatively high.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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avrcandies
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Posted by avrcandies: Wed. Aug 16, 2017 - 05:08 PM
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Jim--you might find this info extremely useful

 

http://cstars.metro.ucdavis.edu/files/3613/4419/0702/Lecture_3-Leaves__Plants.pdf

 

Was wondering, if you do this at night (as mentioned), do the color absorption properties (due to photosynthesis) change while the plant is fast asleep? 

I've asked, but they aren't talking :)

 

Working with the sun is easier than working against it, that's for sure.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ka7ehk
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Posted by ka7ehk: Wed. Aug 16, 2017 - 05:24 PM
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That is a very useful reference. Thanks.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Paulvdh
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Posted by Paulvdh: Thu. Aug 17, 2017 - 05:44 PM
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I just happened to bump into an atricle about "agribotix"

https://www.sparkfun.com/news/1537

 

"Agribotix"  is a company which analyses pictures of crops for growth / health / yield / ... . and you can see some interesting results on youtube.

But a better search term seems to be "NDVI" Normalized Difference Vegetation Index

https://www.youtube.com/watch?v=...

 

Or "Spectral remote sensing"

https://www.youtube.com/watch?v=...

 

This reminds me:

The Raspberry pi camera comes in 2 versions. One with, and the other without an internal IR filter.

Normal camera's have IR filters because the silicon sees further into the IR spectrum than the human eye does.

Even with those filters you often get a bit more IR. That is why you can see the light from IR remote controls with a camera.

 

With "survleillance" camera's it's pretty common to have a little motor move a coated glass filter between the lens and the sensor.

IR filtered out during the day for better color reproduction.

IR not filtered during the night for catching more light.

 

Taking pictures gives soo much more info than a simple sensor.

In #27 you say that your previous device "failed" because of too much variance. Could that variance have been from too much background light, too much light reflected from branches instead of leaves, etc.

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

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ka7ehk
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Posted by ka7ehk: Thu. Aug 17, 2017 - 06:00 PM
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The "failure" was because I was attempting to measure incident light in order to determine reflectivity at different wavelengths. My incident light sensor had a very different field of view than the object being observed. Some times the incident sensor was shaded while the object was not, and so forth. Things were just too uncontrolled. Hence, the idea to "control" things better by actually supplying the incident light (at night).

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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avrcandies
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Location: Cincinnati Oh
Posted by avrcandies: Thu. Aug 17, 2017 - 06:10 PM
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My incident light sensor had a very different field of view than the object being observed

Could be some optics & a beamsplitter might  help, but $$$.  Doing it at night seems the easiest route--it's hard to fight the sun.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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