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post #1 of 48 (permalink) Old 07-28-2014, 01:29 PM Thread Starter
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Help a member out

I want to do a DIY LED fixture...I've bought 50 3w LEDs (700mA and 3.5 Vf) and 55 star heat sinks...I already have an Arduino Uno that I am not using for anything (maybe out will work, haven't looked seriously into it yet) and 3 30mm computer fans

So basically I want to design a lighting fixture that is adjustable in 1% increments that I can control to be on 24/7...and have a 2-3 hour sunrise sunset cycle...and turn down really low to double as a moonlight at night

Am I understanding it right that I will need a 150w driver at 700 mA constant current supply?

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post #2 of 48 (permalink) Old 07-28-2014, 01:45 PM
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yes, that's a lot of lights. You'll also need a driver that'll accept 5v pwm from the arduino to control fading. Something like the meanwell lld driver should work.
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post #3 of 48 (permalink) Old 07-28-2014, 01:48 PM
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Quote:
Originally Posted by Optix View Post
I want to do a DIY LED fixture...I've bought 50 3w LEDs (700mA and 3.5 Vf) and 55 star heat sinks...I already have an Arduino Uno that I am not using for anything (maybe out will work, haven't looked seriously into it yet) and 3 30mm computer fans

So basically I want to design a lighting fixture that is adjustable in 1% increments that I can control to be on 24/7...and have a 2-3 hour sunrise sunset cycle...and turn down really low to double as a moonlight at night

Am I understanding it right that I will need a 150w driver at 700 mA constant current supply?
first off consider a Typhon... or a Corallux controller.. unless you want to go the "uno" path. Basically both the above are built on adruno chassis..
The Typhon has a bit cruder "steps" than the Corallux (at least in theory) but it is reprogrammable.. and all the pieces are there (except serial port to PC interface card)

W/ the Typhon you would have 3 "daylight" channels" and one "moonlight".
$7 CC Meanwell Ldd-h's to go w/ each channel and a PS to match.

So minimum 2 drivers..
Your ps will depend on string length. common 36V PS will allow you to run 9 LED's per string.
Meanwells LDD-H will subtract 3V from the PS so keep that in mind.
your max LED count would be 36 (ignoring using parallel strings at this point) .. though running 9 for moonlight is not really necessary.

Just to touch on the parallel/serial thing.. Using 1000mA Meanwell driver and running the LED's at 500mA you could do 2 series strings in parallel.. increasing your LED density (but decreasing inv. output but NOT by 1/2) by a factor of 2..
Voltage stays the same.. amps are halved between branches..
look up series/parallel led architecture though..


7/per string.. 2 strings paralleled and 3 daylight branches would use your LEd count (42 plus moonlights).. IF you really wanted to..

Last edited by jeffkrol; 07-28-2014 at 01:58 PM. Reason: parallel
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post #4 of 48 (permalink) Old 07-28-2014, 05:01 PM
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why not make your own driver? its not too hard to make if you configure it correctly. that and you arent stuck to just 700mA if you decided you want to lower/raise it. also its perfect for arduino based dimming.

my question for you is, are these leds the ebay specials? the big leds on the star board?


those? i was using those for a while and they run very hot IME. you might need to look at some good heatsink materials for them. and they are only 2.5W leds just to keep your numbers right if you are looking for watts per gallon. also im not too sure on their spectrum for plants i never got to the testing phase of my fixture because i burnt myself on the heatsink (ye stupid me i let it run w/o monitoring it then grabbed it...)
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post #5 of 48 (permalink) Old 07-28-2014, 05:40 PM
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why not make your own driver? its not too hard to make if you configure it correctly. that and you arent stuck to just 700mA if you decided you want to lower/raise it. also its perfect for arduino based dimming.

my question for you is, are these leds the ebay specials? the big leds on the star board?


first he bought "eggs" and stars separate..
second see O2 surplus for variable current driver schematics..
Based on the Allegro Microsystems A6211GLJTR-T "chip"

V(in) is a tad restrictive..
http://www.reefcentral.com/forums/sh...urplus&page=16


TI chip based:
Quote:
I've already tackled that issue with the creation of my LM3409 based driver.
It's capable of driving up to 2900ma and features analog current level adjustment, PWM dimming, and 12V power for cooling fans ect...


fun stuff..



As to your heat issue.. How many and how close were you running them?
9 on a 36" 11/2 x1/8 al barstock @ 700mA only raised the bar temp to 115F...
They are more inefficient than "branded" ones but heat is in relation to current.. Under-driving helps in thermal management.

Last edited by jeffkrol; 07-28-2014 at 05:48 PM. Reason: edit
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post #6 of 48 (permalink) Old 07-28-2014, 05:53 PM
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Well im not looking for help with those leds just a point I made. As for the diy driver I used a small mosfet based cc driver that had an npn feedback to help regulate the current. They work very well if you can get the voltage to within 1v of your leds they are more efficent than the marketed switching regulators... im running mine with 96% efficiency. But if your voltage supplied is far off then the efficiency goes out the window
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post #7 of 48 (permalink) Old 07-28-2014, 06:12 PM
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Originally Posted by genocdex View Post
Well im not looking for help with those leds just a point I made. As for the diy driver I used a small mosfet based cc driver that had an npn feedback to help regulate the current. They work very well if you can get the voltage to within 1v of your leds they are more efficent than the marketed switching regulators... im running mine with 96% efficiency. But if your voltage supplied is far off then the efficiency goes out the window
Life is as simple or hard as we make it..


http://www.pcbheaven.com/userpages/L...ic=worklog&p=3

Quote:
DISADVANTAGES:
Not very efficient since a lot of power is lost across the MOSFET
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post #8 of 48 (permalink) Old 07-28-2014, 06:36 PM
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as i stated they CAN be efficient if you know how to configure them. thanks for posting a picture for it... TBH mine is a little different but the same idea is there. its a cheap and solid driver. i like it better than those switch regulators too because they dont throw off the power factor any.

sorry if i sound like im trying to sound all jargony.... im an EE/CS student going for my masters. the way i described it was the best way i could lol.
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post #9 of 48 (permalink) Old 07-29-2014, 08:54 AM Thread Starter
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Wow...so much thought into this....but I'm just looking for simplicity...would my original idea not work? All LEDs on a single "string" that can all be on and all dimmed?

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post #10 of 48 (permalink) Old 07-29-2014, 09:16 AM
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I am a fish out of water on the technical side of this post and I admire those who are able to master these parts as I have not been able to do in over 40 years of fish parenting. Having said that I am weary of a 24/7 photo period. Plants do better with at least 5 hours of total darkness, not to mention controlling algae. If you read ten posts you'll find ten different takes on this. I can't prove it, as I can only speak from experience. I hope you find some way to factor that in to your project.

Best,

Joe
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post #11 of 48 (permalink) Old 07-29-2014, 10:39 AM Thread Starter
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I understand what you are saying...but I think you misunderstand what I am trying to do here..plants have a certain threshold where photosynthesis stops because they do not get enough PAR "energy". I am trying to mimic nature in that plants do not ever get "total" darkness...


I don't want a 24 hr photo period, I want 24 hr light

As far as the technical side goes...I could honestly figure all of this out myself (I'm an engineer)...but I want to avoid the pitfalls, save the money and make this as easy as possible from the beginning

Isnt that the purpose of a forum? To learn drom other's experience?

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post #12 of 48 (permalink) Old 07-29-2014, 12:01 PM
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Wow...so much thought into this....but I'm just looking for simplicity...would my original idea not work? All LEDs on a single "string" that can all be on and all dimmed?
175V DC @ whatever current you want to drive them at. ... That is what you would need to put 50 LED's on one series string...

5 series parallel strands and you can use a 36V power supply @ whatever Amps you want to drive them at X6

The math is simple V(f) adds in series.. Current adds in parallel..

Again there are catches to series/parallel.. but nothing a few added circuits can't fix (fuses and current equalizers)..

current matching B:


http://edn.com/Home/PrintView?contentItemId=4424539

Summary
Quote:
Driving parallel strings of LEDs pose additional design challenges over single strings, such as tolerating voltage imbalance, current regulation methods, minimizing power dissipation and fault conditions. The simplest way to drive parallel strings is with a fixed voltage source and a series current-setting resistor. When higher performance and protection features are required, individual string regulation offers the highest level of regulation accuracy and flexibility. The final circuit shown reduces power dissipation by regulating the headroom of the current regulators as well as detailing protection and fault circuitry.
Constant voltage parallel array..


Problem comes in finding a Constant voltage PWM dimmer (and cost effective one) for that high of V.. and current..

THE arguably simplest and safest way is series strings on channels w/ a Typhon like dimmer. regardless if you go one power supply multiple drivers or multiple (all in one) units). at least for this size diode..

Last edited by jeffkrol; 07-29-2014 at 12:25 PM. Reason: array
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post #13 of 48 (permalink) Old 07-29-2014, 12:24 PM
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note as long as there are photons to capture photosynthesis never "stops"..
BUT it is not real efficient.. So under low light few, if any, photons are captured, and usually not enough to make a difference..

nothing wrong w/ a complete "blackout" period..or AFAICT a very dim one..
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post #14 of 48 (permalink) Old 07-29-2014, 07:00 PM
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you can always just use a mosfet as a switch, just need to account for about half a volt of drop for it to work right. i think most power mosfets are rated at high voltage and current. they work quite well as a dimmer for the entire thing.
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post #15 of 48 (permalink) Old 07-29-2014, 07:30 PM
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Originally Posted by genocdex View Post
you can always just use a mosfet as a switch, just need to account for about half a volt of drop for it to work right. i think most power mosfets are rated at high voltage and current. they work quite well as a dimmer for the entire thing.


you'd still need a PWM control signal correct??
Or is there a different configuration.

STOP making me learn "stuff"...

http://www.electronicspoint.com/thre...l-leds.239945/
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