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?
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.
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..
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...)
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"
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...
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.
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
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.
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?
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.
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..
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.
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?
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..
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.
ya know no one has asked this yet. what kind of voltage supply will you be using with these leds? ive used spare laptop ones for more of mine. but with all these drivers you will still need a good DC source.
thats a p channel mosfet, so you would need negitive voltage on the gate to operate. i use the 50n06l and it works great. its a N channel power mosfet with very little internal resistance.
edit: now that i read your post a few times heres the deal with the gate voltage. in our case we are looking to work this device as a switch either on or off. the way we can do this is by hitting the gate voltage or slightly exceeding it. i wouldnt recommend anything higher than 1-1.5v over. since the arduino will push the 5v it will throw the mosfet into saturation (ie on) and when the voltage is put to 0 is shuts it off. gate voltage isnt too important with these for what we want them to do is all im trying to say. as long as we dont push too much.
Didnt expect posting this would get such a response/support!!
thank you all so much for being willing to help
I originally planned to do a 3x 16 array of LEDs (48 total) and wasnt particularly sure about a method to dim it using PWM or if it would even be possible
Item List:
-50x 3w 700mA LEDs (received in 1 wk from china)
-50x LED star chips
-Arduino UNO micro controller
-3x 30mm computer fans
Need to get:
-Aluminum heat sink, tho I may just DIY something just because
-wood to build the fixture housing
i havent read threw all those data sheets yet, but if you plan on doing 16 x 3 then you are pushing the ldd-700H to its limits as for output. i would much rahter see you do 6 x 8. that would give you a much more reasonable voltage drop of ~26V vs 52.
I was planning an array of 16 "rungs" of 3 LEDs in series if that makes more sense...then adjusting the power supply down to 9.5v max and constant current...and adjusting intensity with PWM or some other method if necessary
holy heck that might be even more difficult to do, unless you want to use 4 different drivers... unless im missing something else here. because at 700mA each branch, that would give you 11.2A total. for wire you would need something in the area of 18 gage at a minimal. 11.2A is A LOT of current. you really should be looking for some config around 20V and 5A since standard 22 gauge wire would support that.
some one else might disagree with me though. just my common sense kicking in. ive been self taught to stay away from higher than 7A of current or 15KV of electricity. (from stupid personal experiences.)
All those leds ive ever dealt with have a voltage drop of around 3.2v @700mA. So 10v would be fine. I still stand by my diy driver I think I build them for 6$ each not including shipping for each part. If you look in the right places the shipping isnt too bad though
A meanwell LDD-h is $7... And has the PWM circuit ..
Granted you are limited in output more so than custom (w/ out a chip). But you also have a bit more complicated circuit.. (some protection built in)
EMI filtering short circuit thermal protection ect..
Certainly not trying to discourage anyone.. in either direction. Just presenting some pros/cons including a bit on a skills set..
So the plan for now is 6 strings of 8 LEDs...6 ldd700h's...2-3up ldd pcbs...an adjustable power supply at 5A and 36V max...and building a housing for the lights before coding a light schedule
If I can get a "nice" setup for under 400, ill consider this a success
your only running .7A on the strings.. Wire size is not much of a concern... 23 and larger gauge is fine.. (Don't recommend 24Ga but many use it ..Cat 5)
W 4 channels if you want overkill there is 8 conductor "thermostat wire" (Got some at Lowes) 18ga 64 cents a foot...
Another reason to limit to 4 channels..
Cat6 (23ga) would probably do just fine, as long as your not running 10's of feet of it..
you are correct! i dont needYOU at all
..could you kindly gtho of the thread?
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