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LED grow light

  1. Jan 27, 2012 #1
    I recently began making a cabinet into a grow station. It's almost finished, but I'm having trouble with the lighting system. In the beginning the idea was to make a full-spectrum LED light array of no particular voltage. I wanted to mimic this array I saw on LED Lights and Light Fixtures


    Then after I looked into it more I decided to use different types, and colors of LED That would produce the same full-spectrum light pattern. I chose a Warm White, Super Blue, Super Red, and Super-UV. I put links to the specifications of each LED.

    I purchased 3 pieces of aluminum sheeting from Ace hardware and made 3 panels to mount the LED in.


    These two are {18x9} in and have 99 holes {(11x9)} {Length x Width}

    They will hopefully end up looking like this.


    The other panel is { x } with 84 holes {(7x12)}


    This is what I'm planning.


    P.S. Here a link to an LED series or parallel array wizard

    I don't have much knowledge on the subject and need help. Please feel free to give your input.

    Moderator note: Replaced oversized images with links to the images and cleaned up the post a bit to make it easier to read.
    Last edited by a moderator: Feb 1, 2012
  2. jcsd
  3. Jan 27, 2012 #2


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    Good idea, if I were you I would draw a grid with a yardstick, then take your aluminum to someone who has a nice drill press, you will get perfect holes at the perfect angle for your leds, please keep us informed of you out of pocket expense for LEDs, wiring, etc... BTW, I am looking for a solution similar to this. I am betting you can make a decent replica of what the add advertises for about $ 150 US dollars. See if I am correct. Then, all is required is time and labor on your part. If you get it done and want some ghost pepper seeds to start as an experiment, PM me and I will send you some.

    Rhody... :cool:
  4. Jan 27, 2012 #3


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    You seem to be working on the premise that the plants you intend to grow will do best under full-spectrum lighting. This may be correct, I don't know. But if that's not correct, then it might mean you are not maximizing your bang for your buck. Have you done a google search to find the optimal spectrum of light for green plants, or for those that you plan to grow? It may be that one or more of the colours you have used might be better replaced by another, if plants do better with a narrower spectrum.

    If you mix LEDS like this, knowing that different LEDs have different voltage/current requirements, how are you going to power them? Obviously you will reach a compromise, but it may be even easier if there were fewer colours, or if you used equal numbers of the different colours.

    I suppose you'll be buying high efficiency LEDs so that for a given power usage you maximize the radiation?

    Do you have an arrangement that can raise and lower the LED plate so that it can be kept really close to the upper leaves of the plants as they grow? If so, maybe it would be better to group one LED of each colour in a close cluster, and replicate this multiple times, instead of going for a geometrically-pleasing design. As it stands, plants on the perimeter will receive minimal UV, and plants in the centre won't get much RED. LEDs are much more directional than light globes, so each LED will deliver most of its light directly down. This might encourage plants to grow more spindly as the uppermost leaves block the light and the lower ones are shaded and get little.

    What design do you have for the power supply?

    Good luck with you plans to have home-grown lettuce in mid-Winter!
  5. Jan 27, 2012 #4


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    You also will need a heat sink, think, C channel aluminum, stacked side by side and a decent fan to dissipate the heat, have a look here, this may give you some ideas.

  6. Jan 27, 2012 #5
    Plants grow best in a mixture of red and blue light. You don't need the full spectrum.
  7. Jan 28, 2012 #6
    Hey, glad to see people posting on here. thanks rhody that link was pretty interesting,but I

    would use this compound as a heat-sink

    I need lessons on wiring LEDs

    I have no clue how to power the arrays, or what I would need to power them. (driver,ect)

    weather to do them all on a separate power source or all together. (if that's even possible)

    I guess the Main question I have and the reason for this post in the first place is to find out

    If this is possible and if so how to do it. :biggrin:
  8. Jan 28, 2012 #7

    jim hardy

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    Find what is forward voltage drop of LED's at their operating current
    not max current, something less so they'll last a long time

    Connect enough LED's in series to get near a convenient voltage - maybe 12 volts is convenient ,
    so you'd make a string that's nine or ten volts

    Now add a resistor to the string that'll eat up the remaining two or three volts.
    V = I X R
    so resistor needs to be (volts you need to have eaten) / (amps you decided to use)
    and watts eaten by resistor will be (Volts Eaten) X Amps, so buy one rated twice that many watts.

    Make as many similar strings as required to accomodate all your LED's
    and connect them in parallel.

    Now add up the amps
    and go looking for an inexpensive power supply
    of that voltage and current.
    Plenty of surplus sites carry them.
    example: http://www.mpja.com/12V-17A-Phihong-Power-Supply/productinfo/18091+PS/

    A 12 volt 6 amp battery charger is about thirty bucks at Tractor Supply
    and will limit current should something short out.
    Try it first though , some of them hum a bit.
    And it'll actually make around thirteen volts.
    Last edited: Jan 28, 2012
  9. Jan 28, 2012 #8
    The LED specs are linked in the post. I appreciate the advice, but maybe you would have some as pertaining to my specific project?
  10. Jan 28, 2012 #9


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    Please make sure that you do not post images larger than 800x600 pixels, please resize your images.

    Also, the lights you posted are only 5mm and from everything I've read, they will not be strong enough, you need 10mm - 1watt lights.

  11. Jan 28, 2012 #10

    jim hardy

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    gosh i thought you'd be using higher power m Luxeons or something.

    well. i see forward voltages of 2.2, 3.5 and 3.2 volts at 30 milliamps.

    one of each in a series string would add to 8.9 volts

    IF you selected 12 volts as convenient,
    your resistor would eat the remaining 3.1 volts
    R = V / I = 3.1 / 0.03 = 103 ohms, 100 or 110 is nearest standard value
    power is only 0.093 watt so a 1/4 watt will do...
    To accomodate your 84 (was it?) lights
    you'd need 28 such three light strings (each with its own resistor)
    and current draw would be 0.03 X 28 = 0.84 amp

    which you can get from a thrift store wall-wart supply , aka plug transformer
    Look for one rated 12 volts, 1000 ma or higher.

    that's the method. Have fun!
    Last edited: Jan 28, 2012
  12. Jan 30, 2012 #11
    looked over all of the responses and tweaked the design slightly.

    I am completely new to this and all of the feedback really helped.
    Now that I looked into it a little more I see 1 Watt LEDs would ultimately produce the best plants, so I ditched the 5mm and went with these. RED 630nm, RED 660nm, Blue 450nm, and Warm White.

    This was originally the array with 84 LEDs. It now consists of 70 1 Watt LEDs .


    I know that the diagram above is NOT correct.

    My question, is this possible or am I just pipe dreaming.
    I know that I need some form of current limiter, or driver, but im not sure what exactly.

    is there anyway to use a smaller power source for this project? if so please let me know!

    I really appreciate all the input I can get on this project thanks in advance!
  13. Jan 31, 2012 #12


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    Were I to build this, I would want to tweak the currents under full operating conditions by, e.g., tapping along an 82Ω with a string of small resistors in series. Otherwise, he could end up with currents being double what he'd planned for. A 12v wall wart could be anything from about 10.5v - 13v under full load, and small differences in diode voltages may accumulate.

    In practice, the convenience of having a current source feeding each string may well be worth the extra effort of constructing it.

    I'd look for a switched mode wall wart, much cooler running than the heavy iron + copper block.

    OP needs to calculate the heat dissipated in the lights, too. Plants would probably enjoy a little warmth, but not excessive heat.

    Also, OP hasn't addressed some questions I raised.
  14. Jan 31, 2012 #13

    jim hardy

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    Your diagram is a good start...
    just needs something to control current in each row.
    There's always more than one way. The resistors i suggested are simplest, and cheap.
    There are exotic LED drivers you could use
    but there's no way to drive it with less power than it puts out.
    You can use one supply, or several smaller ones.
    How much current do you want through your led's?

    Here's a fairly beefy supply. its datasheet says it'll adjust +-10% so it should make 26 volts okay.
    and another, beefier yet.....

    both are regulated so should hold constant voltage.
    dont use an unregulated one for LED's for reason NascentO2 mentioned,
    unless you use constant current drivers instead of resistors to set current.
    7805 datasheet shows how to use it for that purpose, but you'll want a 28 volt supply in order to have enough "headroom"

    check hobby and surplus sites.
    Last edited: Jan 31, 2012
  15. Jan 31, 2012 #14


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    This is overkill to the nth degree but will give you something to think about as you put together your light project, who knows, maybe it will inspire you to more lofty goals, PlantLab
    Cool technology, heh ? I plan to do more digging later and will report anything I think may be useful to you in your project.

    Rhody... :cool:
  16. Feb 1, 2012 #15
    I've finally decided how i'm going to assemble the 70Watt (70x1W) LED array.

    That dose not mean that I am ready to build it, not even close. I am posting this method so

    that you guy's can let me know if it will work, and it probably isn't the most efficient method

    so please, let me know, I am open to suggestions.

    However if this is a really good way to wire em up then please let me know what

    components i'm going to need, what I might need to know, I mean anything that can help.

    All of the information on the LEDs in on this thread.

    The image of this array is link to the site hosting it, and on that site you can edit so if you

    ever wanna use that too respond to this post you can.

  17. Feb 1, 2012 #16

    jim hardy

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    only trouble i see is your white LED's are 750 milliamp

    and others are 350 milliamp

    so the white ones will be not at full intensity (probably okay)

    check LM7805 datasheet for how to use it as constant current driver

    and i count up 3.5 amps load

    and please go back and either shrink or delete those [too wide wide wide ] pictures so this thread fits on a screen
  18. Feb 1, 2012 #17


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    Jim, kamko,

    kamko can't they are locked at this point only a mentor can re-size them.
    I sent a report to them, hopefully one of the mentors will be so kind as to re-size them.

  19. Feb 1, 2012 #18
    I couldn't Edit the previous post so heres the diagram again this time the wiring may look a

    little more correct.

  20. Feb 1, 2012 #19
    Very cool project! I hope you are learning a lot about electronics along the way.

    The array calculator in the original post is very cool as well. my suggestion is that you dont necessarily need to connect adjacent LEDs to eachother electrically, you could group them by color and then use the LED array calculator to determine how many rows you should have and what resistance to add in each row for current limiting.

    to make these currents more similar you could wire 2 of each 350mA LED in parallel, so that 700mA total would flow through the combination, providing more current to the 750mA LED, boosting its intensity.

    If I were going to design something like this I would probably use something like an old PC power supply to get 12V, wire as many LEDs in series as I could such that the combined forward bias voltage drop was about 10V, put a little LM317 as a constant current regulator, and then repeat that as many times as I need until I have the right amount of LEDs. That way it would be super cheap. ~$20 for 50 LM317s, ~$20 for the power supply (unless you have them lying around like me) plus the cost of the LEDS and mechanical components.
    for a regulated current of 350mA us a 3.6 Ohm resistor, for 750mA us 1.6Ohms
  21. Feb 1, 2012 #20
    Hey guys. Thanks for all the posts and advice, but I have a specific question I need help with.

    if you look at the most recent diagram you'll see I'm planning on using

    10 constant currant drivers to run each series of 7 LEDs in parallel. Okay got that figured.

    Now i'm having issues with the power supply. I don't know how I am going to wire all of

    Those currant drivers to one power source.
    please if anyone knows please reply.

    Jim, I saw that my LEDs weren't the same currant and am now looking for replacements.

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