Help with LED

[stevek]

Hi,
I have been out of the electronics for several years now, but dabble when i need to repair something. Right now i am investigating building a light array of LED's that i can adjust intensity as well as frequency in the red and blue freq ranges.

BUT i am somewhat overwelmed with starting it.
THe parts have changed over the past 15 years and I am not sure what to get and information is lacking out there.

Anyone got any ideas or suggestions?
Steve

[Roger Dodger old codger]

You can start with this site
http://www.theledlight.com/technical.html

yep things have changed in 15 yrs. BIG TIME.

EVERYTHING

rogerdoger

[Newz2000]

Originally posted by Roger Dodger old codger:
yep things have changed in 15 yrs. BIG TIME.

EVERYTHING

rogerdoger

Yeah, now electrons go from the negative terminal to the positive. What a surprise!

[Gorgon]

Yeah Matt, didn't you know that electrical current is made of holes?

No joke!

TOK

[stevek]

Heh, they went from neg to positive back in the stone age too! :p

Originally posted by Matt Nuzum:

Originally posted by Roger Dodger old codger:
yep things have changed in 15 yrs. BIG TIME.

EVERYTHING

rogerdoger

Yeah, now electrons go from the negative terminal to the positive. What a surprise!

[stevek]

Amazing, spent the morning going over LED's and wow!
Now i have no idea what i need to accomplish what i want.

grrrr.

[Gorgon]

Originally posted by stevek:
Hi,
Right now i am investigating building a light array of LED's that i can adjust intensity as well as frequency in the red and blue freq ranges.

Hi Steve,
I've never heard of LEDs you can change the colour(frequency) of. But if you use a red and a blue LED close together and use individual PWM on them, you should come close to your requirements of changing the colour and intensity. I think you need to do some experiments on this.

Looking forward to hear about the solution and result.

TOK

[Chris Smith]

You will need to buy red, green, white and blue LEDs in order to get or mix more colors.

You can mix them to make other colors past the RGW&B, but a defusing lens is usually needed to make it blend a little better, depending on distance away from the LEDS or perspective angles and motion.

The closer you are the more you can “See” that the color is made up from individual LEDs, where as distance or a diffusing lens tends to blur them into a paint palate of mixed color.

Also varying the pulse length, power, current etc., to each of the LEDs will increase/decrease the brightness of the LEDS and thus it will change the hue of the output color based upon [dilution] the intensity differences. Just like mixing paint.

<small>[ November 12, 2005, 09:29 AM: Message edited by: Chris Smith ]</small>

[Newz2000]

There are RGB LEDs and you can control the intensity of each color channel independently. The way I've heard of this being done is through PWM but really, any way that changes the current should work.

They have four leads. The challenge is to find the true RGB LEDs that you have control over. Often times you find LEDs that have two LEDs and blink and/or change color automatically. I have no idea why someone would want that, but they're phenomenally more common that the true RGB LEDs.

Even though I can't quite find any such LEDs for sale at the moment, here's proof that I'm not crazy: http://www.rgbled.org/

I doubt this is a good "sticking my toes back in the water" project. This is more likely a "skinny dipping at Niagara Falls" project. It looks fun though! (the LED project, not skinny dipping at Niagara Falls)

<small>[ November 12, 2005, 03:53 PM: Message edited by: Matt Nuzum ]</small>

[Newz2000]

By the way Steve, welcome to the forum. I'm sure there are many people who are eager to help you out. Could you give a little more detail about what you're trying to do? Your reference to frequency is throwing me off a little bit.

Let us know what your goal is and maybe some idea of how you think you'd go about it. If you're nuts, don't worry, someone here will let you know. I too have started getting into electronics after a long time away. The biggest new thing for me has been microcontrollers and how you can do some amazing stuff with a little software and a $3 chip.

[Gorgon]

Hi Steve,
If you want to make a full colour light, I think this LED could be used, with proper optics.
http://www.everlight.com/pdf/15-23BSURS ... A2-TR8.PDF

It's just an example, but I think you get the general idea. Using 3 PWM outputs, you can make any colour and intensity. Inside the LEDs limits. If you want more output, you could combine your own high intensity single colour diodes to a RGB cluster. Depending on the viewing distance and extra optics, it may look as a single point.

TOK

[stevek]

Hi,
Well I have a nursery and some of the plants i grow need better lighting conditions to get them to grow right.
Plants grow better when their in the blue and red frequency of light, during the late spring, summer, and early fall they can filter out the rest of the bands and take in the needed bands. In winter though, there isn't enough hours of light as well as the light is coming from a angle further south than overhead like in summer. Hence the intensity!
I have priced lamps and these folks want several thousand dollars for lamps, heck a bulb runs around 180 bucks - 300 bucks and i need 6 reds and 2 blue per 4'square foot.

Just was trying to see if i could make my own and mix and match my own blend to get the best growth too instead of buying a canned bulb that grows certain plants good and other suffer.

It also gets old having DEA showing up to search my greenhouses everytime i order some hydroponic device! Thats getting real old!
Steve

<small>[ November 12, 2005, 04:26 PM: Message edited by: stevek ]</small>

[Newz2000]

I don't know how big of an area you want to cover, but the full spectrum LEDs aren't that cheap, and most LEDs, while bright, cover a relatively smaller area.

Have you checked into the fluorescent tubes used for pet lizards? I understand they're very similar to the lights used to make plants grow and can be purchased much cheaper than $180.

I'm sure there's some benefit to the bulbs that run so much, but you may find cheaper bulbs at a petstore or mailorder business that caters to reptiles.

10 years ago I found "grow lights," incandescent/halogen bulbs that produced the correct light to help plants grow indoors. Home depot wasn't around my area then, but I'd look there to see if they have them.

[Robert Reed]

A little off the topic, but the remarks about current flow caught my interest. This has long been a topic for debate--Conventional current flow vs. electron flow. I myself prefer to think in terms of electron flow as this is what actually is moving. But heres an interesting analogy--An egg carton has one egg missing. If we remove an egg adjacent to that empty hole and place it into that empty hole and then keep repeating this process, we have eggs moving in one direction and holes moving in the opposite direction. So, are we moving eggs or holes?

[MrAl]

Hello there,

On Topic:
Led's dont light that big of an
area, so it would take many, many LED's to
do plants! There is always Lumileds i guess.
It's still going to cost a bunch to do a wide
area.

Off Topic:
ROBERT REED:
You originally said you were moving 'an egg'
from one position to another, therefore the
answer to your question is:
"we are moving eggs".

See how that works so nicely?

Proof?

Take a FULL dozen of eggs, move one egg from
one place to another. We've moved eggs again.

Now take an EMPTY dozen egg carton, try moving
one hole from one place to another. There's no
way to do that.


Now we could argue:
"Yes, but when there exists
a partially empty egg carton (one egg missing)
when we move one egg one hole appears to move
also."

Note the use of the word "appears"
When we move the egg from one hole to the next
and then examine the container it appears that
one hole has moved in the opposite direction.

In fact, what happens when one egg is moved from
one position to the next?
In moving from position A to B the egg takes on
many positions inbetween A and B, while at some
points between A and B the 'hole' becomes two!
Consider when the egg is half way between A and
B...
Alas, there are TWO HOLES NOW! Yikes, so really,
if we want to be really accurate, we have to
say that in moving an egg we first creates two
holes, then fills one hole so there is a 'new'
hole located opposite to where we moved the egg.

The conclusion is that the 'hole' doesnt really
move, but in fact a new one is created when
the egg is moved.

Now when we temporarily exit reality and dive
into theory, we can say that maybe the positions
from A to B dont matter in any phyical problems
we are interested in, and will probably never
be interested in (although that's a jump).
This means we can say that the only thing that
matters (theoretically) is that the egg gets
from A to B, so that the 'hole' does in fact
move from B to A, but only in theory.

Thus, when we ask the question "what really moves"
we have to ask that question within the context
of what application we have in mind for the
answer: either 'total reality' or 'theoretical
reality'.

On the other hand, if it can somehow be proved that
these two realities are the same thing (and
this is a long shot knowing that particle
physics is still changing) only then can we
say the hole 'really' moves 'for all purposes'.


Hope this sheds some light on the subject, and
feel free to comment.


Take care,
Al