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Living the Life!
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Discussion Starter · #1 ·
....... that you can see the light emitting from an IR LED on a Scalextric car?


I was fixing up some LEDs one evening whilst trying to photograph the emissions from an IR LED to see if I had wired correctly. As I sat in my darkened room room I noticed that the LED gave off a very faint but deep red colour, almost the shade of stale blood.

You will need to have the lights off for a couple of minutes for your eyes to obtain their best night vision and get the PB and car set up before hand. Often just taking the body off is sufficient.
 

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Discussion Starter · #3 ·
Yep ...... BBC1
 

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Visible light, "Dark Red" has a wavelength of 750nm. The Infra-Red LED used by Hornby is towards the bottom of the Infra-Red spectrum and has a wavelength of 875nm. However they have a relatively broad spectrum and although well down on output there will be some radiation in the visible spectrum.


You also see this effect with some security lights, which is why 950nm is often used to make them completely invisible to the naked eye.

Rich
 

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I must be a freak (okay, I know I am, but you know what I mean). I'm pretty sure I can see most of my cars LEDs under normal incandescent lights.

Now I think of it, as long as the object is further away than my arms length, I have got eyes like an "out"house rat. Scientific test next wednesday when the lads come around for a race. After the beers have been opened.
 

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... Rich - I suspect ever fewer people knew that as well


... Martyn is that your Owww testing mate??
 

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That's how I testto see if the LEDs are working on the Scorpius system, by turning the lights off and having a look

(880 nM)
 

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If you look at an IR LED through a cell phone camera, it emits blue light when active. Check it out. Crazy stuff!

Cheers.
TK
 

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Discussion Starter · #9 ·
...... the human eye perceives very bright white light as blue ........... now that is freaky.

Remember the washing powder adverts describing their whites as "blue-white"??
 

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Not so freaky when you consider that "daylight" bulbs used by photographers are actually blue. These give a better colour rendition than white light simply because, if you think about it, what colour is the sky?

As we can see things that are not lit directly by the sun we must be seeing these things lit by the sunlight diffused as blue by the sky. Colours are "flatter" or less vibrant under a grey sky which is why we perceive a cloudy sky as slightly depressing.

What is a proper colour is a matter for interpretation but as people often take stuff to shop doorways to see their "proper" colour in natural daylight then I guess blue is a more natural light than white.

If you want freaky - then try this.

Next time you see a completely blue sky; face towards the sun then spin slowly though 360 degrees noting how blue the sky is. You will find it is its deepest blue at 90 degrees to the sun. So if you want to get the bluest skies in your holiday snaps (or to keep the Mods happy - to shoot your slot car on your garden wall with the bluest sky as a backdrop) make sure the sun is directly to your right or your left.
 

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Yeh, 850nm LEDs glow almost baby pink when viewed through any form of CCD in a digital camera. I test my light bridges as I make them this way.

- Although there is a new one out in China which I can see easily in dim light with a bright pink/red pin of light in any dull lighting situation.
It has a frequency spec. very similar to the black-light LEDs, but being without any filter in the bulb they are more visible.
 

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Nano Metre, 1/1000000000 of a Metre, quite small.


Rich
 

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Life ..........


I am a First Aid trainer with the Royal Yachting Association and an Enhanced Skills First Aider with the British Red Cross.
 
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