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LED light

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thejuggla1

New Member
I was going to design a grow light made out of LEDs as seen here

http://i233.photobucket.com/albums/ee268/Allan-2greasy/Panel2.jpg?t=1248392744

Planning on going with 10mm LEDs

Red - Red LED (46 in total)
Blue - Blue LED (20 in total)
Purple - UV LED (14 in total)
Orange -Infra Red LED (10 in total)

I was going to set it up like this, but obviously a lot more LEDs, just making sure I have the right way of setting them up, if there is a better way please help me out (Sorry this diagram is terribly bad and probably a bit wrong but I hope you can understand it) Just use your mind to add on the extra LEDs theres going to be 46 red, 20 blue ect.

http://i233.photobucket.com/albums/ee268/Allan-2greasy/diagram-2.gif?t=1248393445

And Do I need capacitors or is it fine without?

How do I find out how many ohms the POT should have for each section of lights so it can be completely shut off or dimmed to any ammount? (So each color can be dimmed on its on, so Red's Pot is different from the Blue's POT)

Whats the best way to tell how much amps a certain gauge of wire can hold?

I was told glass LEDs last longer than plastic, is this true? How do I tell the difference between glass or plastic when ordering from a site?

If the place I'm buying from doesn't give me the current or voltage needed for the LEDs is there another way to find that out?

I'm planning to do this off a old computer power supply, my voltage meter says the red wire on the power supply gives me 5.3 V but on the case it says it puts out 5v, should I use the resistance for what the power supply says it should give out or for the reading I am getting

I chose a computer supply because allows other addons for people that can't do this kind of stuff such as a miniature computer fans and also since it gives off enough power to power multiple of these lights.
 
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RODALCO

Well-Known Member
Firstly there are no glass 5 mm Ø led's.
The clear 5 mm Ø leds are made from plastic.

The 5.3 volts voltage is the open circuit voltage of your supply. It will drop to 5 volts with some load applied.

Keep the current through your led's to below 20 mA. go for about 15 mA.

red 1.7V
blue/purple 3.0V
orange 2.2V

You get awa with 2 led's in series for the red and orange ones.
Then by U-I*R
use a 106 ohm series resistor 100 or 120 for red.
40 ohm 39 or 47 for orange.
133 ohm for a single blue/purple use 120 or 150 ohm.

Always good to check Led current with a mA meter.
 

bountyhunter

Well-Known Member
Don't often see the words "grow light" and "POT" in the same post...... somewhere a government monitoring system just perked up it's electronic ears!:eek:
 

RODALCO

Well-Known Member
A pot is not the most efficient way to directly control led's, although it is the simplest method.

It is better to have the pot control a transistor which can drive the led's in a series parrallel arrangement.

so 4 pots, 4 transistors e.g. BC 140 and 4 base resistors are needed to drive the leds strings with their own series resistor (values as above)
 

RODALCO

Well-Known Member
polarity

I just noticed that the polarity in your drawing is the wrong way around.
 

audioguru

Well-Known Member
Most Helpful Member
A pot will quickly burn out when it tries to provide power to that many LEDs.
Usually a pulse-width-modulation circuit is used as a dimmer.

Why use purple LEDs when the red and blue LEDs add to make purple?
 

Hero999

Banned
Why use purple LEDs when the red and blue LEDs add to make purple?
He isn't using any purple LEDs, he's just used the colour purple to indicate UV LEDs on the diagram.
 

HarveyH42

Banned
I've done some reading on this, and you should read some more on the subject. Plants only use the red and blue. 5mm LEDs aren't strong enough, should look into 1 watt or more.
 

thejuggla1

New Member
Firstly there are no glass 5 mm Ø led's.
The clear 5 mm Ø leds are made from plastic.

The 5.3 volts voltage is the open circuit voltage of your supply. It will drop to 5 volts with some load applied.

Keep the current through your led's to below 20 mA. go for about 15 mA.

red 1.7V
blue/purple 3.0V
orange 2.2V

You get awa with 2 led's in series for the red and orange ones.
Then by U-I*R
use a 106 ohm series resistor 100 or 120 for red.
40 ohm 39 or 47 for orange.
133 ohm for a single blue/purple use 120 or 150 ohm.

Always good to check Led current with a mA meter.
OK so many more questions

I thought electronic component only drawed amps it needed? It can over draw? How do I keep my LEDs below 20/15Ma?

The voltage for the LEDs will always be the same whether It is some cheap LED that has a color case, or a clear one that produces the same color?

Does infrared count as orange? Or did you miss understand the diagram?

Is it ok just to parrell them all or should I do 2 in a series like you said?

So a POT would work but I need a transistor for each POT? How will that look like on a diagram? Or is another alternative cheaper?

Sorry for putting the LEDs the wrong way I warned you I might of had it wrong.

And to the other people, I'm pretty sure plants use UV(UV is The closest you can get to real sunlight right?) and infrared, and this isn't for me selling these to friends so I don't know a whole lot about growing
 
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audioguru

Well-Known Member
Most Helpful Member
You need to learn about the colors of light and the amount of light that plants need.
You also need to learn about the voltage and current ratings of different color LEDs.

I don't know if anybody sells huge powerful rheostats anymore since an electronic dimming circuit will do the dimming with an ordinary small inexpensive pot.
Plants don't need the light to be dimmed.
 

Hero999

Banned
Or did you miss understand the diagram?
Yes, I think that many people here have misunderstood the diagram.

I know you're not using any orange or purple LEDs, they're just the colours you've chose to represent the infrared and ultraviolet LEDs.

Iinfrared LEDs have a lower voltage frop, about 1.2V.

This means that when running from 5V, the UV and blue LEDs all have to have their own resistors.

You can connect up to three infrared LEDs in series or two red LEDs in series and just use one current limiting resistor.

You could connect the IR LEDs as three strings of three in series plus an extra one on its own.

The red LEDs could be connected as 23 strings of two in series.
 

thejuggla1

New Member
Plants don't need the light to be dimmed.
I heard blue is better for veg. still confirming all this stuff though.

Hero999769663 said:
This means that when running from 5V, the UV and blue LEDs all have to have their own resistors.
Ya I know that part, but your confusing me about saying keep the current through my LEDs 20-15MA I thought they never drew more than needed?
 

audioguru

Well-Known Member
Most Helpful Member
Ya I know that part, but your confusing me about saying keep the current through my LEDs 20-15MA I thought they never drew more than needed?
An electronic circuit is designed to draw only as much current that it needs.

But an LED will draw way too much current so that it instantly burns out. You need a series resistor or a constant current source circuit to limit the current to about 20mA for an ordinary LED.
 

audioguru

Well-Known Member
Most Helpful Member
So I need A resistor for the voltage then one for the current? I am confused.
No.
LEDs limit their own voltage. You need to use a series resistor or constant current source circuit to limit the current.
 

audioguru

Well-Known Member
Most Helpful Member
So I don't get what your saying, each LED needs its own resistor?
If your voltage is high enough you can connect many LEDs in series and in series with a single current-limiting resistor. Then the same current flows in each LED.

If your voltage is about 1V higher than your LED voltage then each LED needs its own current-limiting resistor.

If you connect lEDs in parallel then since they are not exactly the same the one with the lowest voltage will hog most of the current and instantly will burn out. Then the LED with the next lowest voltage will burn out etc.

Manufacturers of LED flashlights test and sort their LEDs so that each flashlight has LEDs with exactly the same voltage and they are connected in parallel.
 

audioguru

Well-Known Member
Most Helpful Member
Your LEDs are connected backwards.

What is the voltage range of your red LEDs? Pick the lowest voltage (maybe 1.8V for red LEDs) then two in series need 3.6V.

The current-limiting resistor will have (5V - 3.6V)= 1.4V across it.
Ohm's Law says that the resistance must be 1.4V/20mA= 70 ohms. 68 ohms is the closest standard value.
A single LED will need a resistance much higher. Calculate it.
 
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