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1104 led rectangular array

Discussion in 'LEDs and Optoelectronics' started by serge53, Dec 30, 2011.

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  1. serge53

    serge53

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    Dec 30, 2011
    hi there!

    im in need for some information. i plan on building an array that has 1104 leds, i want it to be 22 leds x 46 leds spaced 1" apart. i want to use 736 red and 368 blue.

    the problem im running into is i don't know what resisters to use, i would like to use a 12v source if possible.

    im not very familiar with leds.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Please have a read of this and get back to us if you have any questions.
     
  3. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
    Making a Grow Light? There are better alternatives....
     
  4. serge53

    serge53

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    Dec 30, 2011
    yes i am lol. would you care to elaborate? im interested in your opinion.
     
  5. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
    I have never met anybody that had good results using LED's as grow lights., honestly.

    LED grow lights are a big scam, promoted by lying hippies that are just trying to sell you the overpriced crap they sell on the internet.

    If you really want to make the ultimate grow light for your tomatoes:rolleyes:
    I suggest you "google" Plasma Light Source.:D
     
  6. serge53

    serge53

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    Dec 30, 2011
    hmmmm ill look into that. thank you!
     
  7. BobK

    BobK

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    Jan 5, 2010
    I would not take Gonzo's word for that, I would do a little more research. There is certainly no theoreitical reason why LEDs could not be used to make a good grow light. They are now among the most efficient light sources and offer good control over the spectrum produced.

    I do not know from experience whether the LED grow lights on the market are scams, but the fact that the high-end products are moving in that direction makes me think they are not. Even marajuana producing "hippies" are subject to economic realities.

    Bob
     
  8. jackorocko

    jackorocko

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    Apr 4, 2010
    From experience, I can tell you one thing that an LED can't do. It can not penetrate the canopy. The same thing with a CFL or florescent over an HID light. You will get some results with the CFL/florescent, but they will never be as good as their big brothers.

    Gonzo and Bobk both bring up cons and pros. Personally if I was doing today what I did in the past I would stick with the big boys.
     
  9. BobK

    BobK

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    I don't understand this comment. How does the source of the light affect whether or not it is able to penetrate the canopy? Photons are photons, are they not?

    Bob
     
  10. jackorocko

    jackorocko

    1,284
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    Apr 4, 2010
    Photons are photons, I believe everything you are saying. But in my experience I would not waste my time. LED lights would have had to come a long way in 6 - 8 years since I last used one. That being said, maybe they are as powerful as the HID lights these days. I can't deny or confirm that.

    I can't imagine an array of LED's would be as powerful as a 1000W HID light.
     
  11. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    Photons are photons, I believe everything you are saying. But in my experience I would not waste my time. LED lights would have had to come a long way in 6 - 8 years since I last used one. That being said, maybe they are as powerful as the HID lights these days. I can't deny or confirm that. When I say penetrate the canopy, I should have probably been more clear with reflected light.

    I can't imagine an array of LED's would be as powerful as a 1000W HID light.
     
  12. serge53

    serge53

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    Dec 30, 2011
    ok i have a question. maybe this will help me lol. how many leds (2.5v 20mA) can i wire in parallel from a 12 or 24 v source? also how many in series with said information?

    would i be able to wire 46 rows wired parallel and 22 stemming off in series to create my grid?
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    You can have as many as you want in parallel, but in series you are limited by the forward voltage of each LED. (for 24V you can place approximately twice as many in series as with 12V)

    Did you read that post I directed you to? It has links to various calculators to help you with this sort of thing.
     
  14. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
    If you are a hippie...then I apologize!....LMAO!
     
  15. serge53

    serge53

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    Dec 30, 2011
    i did go there but it kinda confuses me lol. ok so i used the chart thing and found i need to have a 44v supply with a 1ohm resistor to run 22 leds (2.0v 20 mA) in series. is this correct? also would i be able to use a 44v supply for my entire panel?
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    There are a number of things you need to know:

    1) the forward voltage of your LEDs. This will usually be specified as something like [email protected] in the LED specs and may be a range of voltages. Take the typical value or mid-way between the min and max.

    This will differ between different types of LEDs, but mostly between colours.

    2) your supply voltage you said 12V or 24V, but it is wise to know the range of voltages which may be present. For example, a car battery may vary from 10V to 14V. Larger variation will make things harder and will also reduce the number of LEDs you can place in a string.

    Then go here

    As your source voltage, enter your MINIMUM input voltage (say 10V).

    As the diode forward voltage, enter the number you got from the specs.

    As the diode forward current enter 20 (20 mA) or whatever current you want to run them from.

    for the number of LEDs in the array, enter a large number, say 100.

    Then click "design my array"

    You will see a diagram showing a number of strings of LEDs and a resistor all connected in parallel. Note the number of LEDs in each string, and the value of the resistor.

    Now go back to your input fields.

    Change the input voltage to the maximum voltage your power supply will deliver.

    Change the number of LEDs in the array to the number placed in each string previously.

    Now hit "design my array" again.

    Note the new value of the resistor -- this is the value you should use.

    You will need to do this for each type of LED you have. Possibly only twice if you have red and blue LEDs which are all the same. Possibly more often if you have LEDs from a whole heap of different manufacturers.

    The problem with using a single resistor like this is that the brightness will fall off quite rapidly with voltage. If your voltage source is stable (i.e. the min and max voltages are very close) then you will have fewer problems.

    After you've done this you will have to wire up the LEDs in many strings and connect them all up.

    I hope that's clearer.

    Whether or not you get enough light at 20mA is another issue. Perhaps you should check the specs to see what the maximum continuous current is. It may be 25 or 30 mA (or even more) and you would be wise to use the max value as stated in the specifications.

    If you don't have any specifications, you need to find another source of LEDs that can provide them. If you've already bought them, you could measure the Vf by estimating the Vf and calculating a resistor which will limit the current correctly, then measuring Vf to verify.
     
  17. serge53

    serge53

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    Dec 30, 2011
    actually you just gave me the answer in needed. thank you very much! you are very helpful.
     
  18. BobK

    BobK

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    Jan 5, 2010
    That was years ago!

    Bob
     
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