best way to sense light on a screen (technology independent)

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#1
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I'm essentially looking for the best way to read a while area on a tv screen. The goal here is not to discriminate from crt/lcd/plasma/etc. I would need to know when the screen (or area of the screen ) goes from black to full white.  The board would be powered via batteries or possibly a 5 volts source (USB) and it must be very resilient to moment. I'm just curios what some of you might suggest?

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very resilient to moment

I have no idea what that means!

 

LDR facing the screen patch that you are monitoring. Comparator and output device of choice.

Ross McKenzie ValuSoft Melbourne Australia

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Just that whatever I use must accept lots of moment as this device will be used by a younger crowd.

 

 I was a bit concerned photoresistores would not pick up a LCD screen in a brightly lit room. I did forget to mention this would need to work for up to 5/6 feet away with a lens that concentrates on a fixed are. 

 

Though I guess if I use the ADC as the Comparator and add a POT to get the right expected value.

Last Edited: Mon. Mar 14, 2016 - 03:00 AM
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must accept lots of moment

I have no idea what "moment" is.... some form of current drug perhaps.

 

Anyway, the 5 or 6 feet specification is a game changer for my suggestion... a very  important specification indeed.

 

I'm out.

 

Ross

 

Ross McKenzie ValuSoft Melbourne Australia

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I guess a camera pointed at the screen and vision processing would be "over-kill" would it?

 

(I don't suppose there's any way to intercept the digital data (I assume?) that is being used to form the image on the screen in the first place?)

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Do all you guys know what a 'while area' is on a screen? The statements inside the braces?

 

Imagecraft compiler user

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It's obviously a typo. He meant "white". Later he said:

black to full white

So I would have thought that was blindingly obvious? 

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I think I'd try one of my Taos/ams color sensors, with a tube and/or lens  http://ams.com/eng/ColorSensor

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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I think it would be better if the OP could tell us what he is actually trying to do?

Why does this area of the screen go white?

Why is there so much movement?

 

Sounds to me like it would be better to access the cause of whatever is indicated by the white area on the screen, and process that instead.

SpiderKenny
@spiderelectron
www.spider-e.com

 

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theusch wrote:
I think I'd try one of my Taos/ams color sensors

Is that really going to work from 5..6 feet away?

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Yes, it will work from 5 or 6 feet away. The sensor will, however, have to be "focussed" such as being in a tube. They have enough sensitivity to do that. I am using a new AMS/Taos RGB_IR sensor to look at flowers blooming and leafs leafing out or falling. The real trick is to design a way that the sensor sees only the desired target (mostly).

 

Less certain is the ability to deal with movement. It obviously won't work if it is not pointed at the target. 

 

Jim

 

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

 

 

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I guess a camera pointed at the screen and vision processing would be "over-kill" would it?

Yeah, a bit too much.

 

Sorry about the types, I need to stay off the these damn androids.

 

while area = white area

moment = movement

 

I think I'd try one of my Taos/ams color sensors, with a tube and/or lens  http://ams.com/eng/ColorSensor

thx theusch, ill tech it out (update: Would you part with a sample unit I can buy? I'm not ready for 1k units but will once the design is ready)

 

The real trick is to design a way that the sensor sees only the desired target (mostly).

I believe that can be done with a lens. I have seen it done before.

 

 

 

I think it would be better if the OP could tell us what he is actually trying to do?

Why does this area of the screen go white?

Why is there so much movement?

Its a device that you aim at a TV  (game) that will read data on a small potion of the screen via a white square (white:1 black:0). The white square will move and you need to track it.

 

 

 

 

Last Edited: Thu. Mar 17, 2016 - 01:21 PM
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Oh.... kinda like "duck hunt" I guess!

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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LOL,  see that is what I'm trying to avoid here.  Now the search argument d*ck h*nt will work ;) I'd like to get the patent out first. Though yes its very close to that. Honestly, I'm not doing anything top secret but I try not to spill the beans too much on a searchable forum.

Last Edited: Tue. Mar 15, 2016 - 09:02 PM
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Back in the day, when I was a lad, 1982 to be precise, I had a "light gun" game.

The gun was basically an ldr at the end of the tube, and it worked based on the principal that a TV scans the image 25 times a second (PAL, UK)

It's only the persistence of vision in our eyes/brains that makes the image look whole.

So to know where you were targeting the gun, it would overlay each frame with a coloured blob - in a different place each frame. The gun filtered on the colour of the blob and by tying up when the gun saw the blob, and the position of the blob on the screen, it could tell where you were aiming.

 

Your eye's did not see the blob, because it was in a different place on each frame.

SpiderKenny
@spiderelectron
www.spider-e.com

 

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Also, thinking about it, the above technique probably wouldn't work on a high-res, high-frequency LCD or computer monitor.

See also https://en.wikipedia.org/wiki/Light_gun 

SpiderKenny
@spiderelectron
www.spider-e.com

 

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That is correct, the technique used back then only worked on CRTs.

Last Edited: Wed. Mar 16, 2016 - 03:10 AM
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Way back when, in what feels like a different lifetime, I used to fix video games in pubs. Atari had a d*ck sh**t g*me c*lled "Qwak!", with a (light detecting)rifle on an armoured cable. If you managed to "hit" the d*ck, it would plummet earthwards, making that noise that all falling things make in cartoons, and a dog would lope along the bottom of the screen and retrieve it. Every single person(and probably the married ones too) who approached while you were fixing this machine would always ask the same question: "What happens if you shoot the dog?"

 

And they say England is a nation of animal lovers...

 

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:

And they say England is a nation of animal lovers...

... or shopkeepers...

Ross McKenzie ValuSoft Melbourne Australia

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Yes, but you can't believe what those frenchies say.
 

Four legs good, two legs bad, three legs stable.

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I have had some success here using the clear setting (all bands of light) with %100 power. It certainly will sense light and does a great job of it. To detect the light from a LCD scree I need to be less then an inch away. I was able to get an assortment of lenses around 1 inch in diameter (may need smaller) and I can cast the image of a white square on the tcs3200 quite clearly from a great distance. Though the device does not sense the change from the black area of the image to the white area.  If I put the lens in a tube it helps greatly with the contrast but still no luck sensing the white square. I may have to look in to other light sensing devices or possibly find the right lens config.

 

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John_A_Brown wrote:

Way back when, in what feels like a different lifetime, I used to fix video games in pubs. Atari had a d*ck sh**t g*me c*lled "Qwak!", with a (light detecting)rifle on an armoured cable. If you managed to "hit" the d*ck, it would plummet earthwards, making that noise that all falling things make in cartoons, and a dog would lope along the bottom of the screen and retrieve it. Every single person(and probably the married ones too) who approached while you were fixing this machine would always ask the same question: "What happens if you shoot the dog?"

 

And they say England is a nation of animal lovers...

 

laugh

Big times! I can remember it!

 

I can remember that I had one of these:

 

 

And these:

 

 

 

 

 

@S_K_U_N_X

Hey

How about a simple Transimpedance amplifier + a simple LED?

 

 

"Hiss Hiss"

"One's value is inherent; money is not inherent"

 

Chuck, you are in my heart!

Last Edited: Sat. Apr 9, 2016 - 06:16 PM