So, that's 25 Leds.. is the 3 watts total or 3 watts per LED?
Assuming 3w per LED, that's 75w of LED light, which is a lot more light than 75w of T8 tubes (which would still be a lot on a 20 with no CO2).
Since you are not doing CO2, make sure you build a dimmer into your design. You are going to want to run those LED's pretty low (maybe 15-25%), unless you hang the light pretty high above the tank.
LEDs are 3w each, every channel dimmable. I will not run them at full power at least for now.
The 10 white led's will be the brightest ones, at 160-200 lm/led, with the red ones at 30lm/led and the blue ones a bit brighter (100lm/led?) at full power.
I plan as channels:
- white
- blue/red (for growth/color accents)
- eventually in the future one/two blue led as nightlight
I will probably purchase some cyan later.
Basically give up the green, reduce the red, group into clusters...
I would never encourage anyone to put the red and blue on one channel..
If you want to cut it down to 2 channels I suggest a red/white channel and a blue/white channel..
The red/white channel being composed of low k LED's i.e 3500k and red.
The blue/white channel being 6500k white or better..
As a start a 2:1 w/r and 2/1 blue/red ratio is a good start..
Same way reefers run blue and white channels for color balance..
Technically a 2 channel design of ww and cw led's is all that is needed:
Ok, I will keep the red/blue separated for now. I would actually plan on using two RGB controllers in the end (I have one now) that can output 12V/2A max/channel, with remote control (those controllers used for RGB led strips). They seem to be working pretty well for 2 white LEDs in series.
I will tap the heatsink so it will be easy to upgrade for future use (mount, changeLED's), and in the future I will get some warm wites, more blue LED's and a couple of cyans. I'll just have to mount it and see how it looks for now.
Thank you for the chart and for the advice. I consulted lots of resources, but any piece of advice is a bit extra.
Those are meant for constant voltage LED "strings"... They will not work "well" w/ 3W emitters unless you keep each string in the 12V V(f) range..
That would be like 3= 3w in series then enough of those strings to keep the current in check.. 2 or more depending on what current you want..
Generally each string of 3 will need a "current limiting" resistor..
IF I understand what you have correctly, you are taking the "hard way" about this..
Constant current drivers w/ PWM dimming and a controller is more the way to go.
A Typhon or one of the "like" controllers is a better, easier, and safer way to go.
,
Yes, I know. I am keeping the strings in the 3V range, that's the only way I can be sure it works. I did some measurements (A and V) from 0 to 20 steps (every channel goes up to 24 steps if I remember correctly), and around step 17 I got around 700mA (I don't remember the voltage, I must have it on a paper somewhere). I have some electronics experience and I am trying to keep my power supplies, drivers and LEDs safe . The red LEDs are opening up a bit quicker, so I will have to put probably 4 of them in series. I will make some measurements and maybe I will use some resistors so I can max out the drive (step 24 on the remote) without killing it or the LEDs.
I will have to go with the drive I have for now, but as you say, I envision using constant current, pwm controllable drivers in the future, controlled by an Arduino, together with other aquarium functions. I do have plans for the future, but for now I want to deal with what I have.
your missing a minor point. The "dimmer" doesn't change current.. it only pulses it. It may average to 700mA but it is feeding all it can to the LEd's...
At least this is how the more common "strip" devices work..
W/out th current limiting resistors all you are doing is pulsing 2A.. or whatever your PS can put out if you are not exceeding the V(f) requirement.. and you won't w/ 3 or less LED's..
In other words it is like 2A w/ a 50% duty cycle averaging to 1A over time.
As an example w/ "real world" LED's.. This is a circuit for a Cree xp-e using a 12v constant voltage power supply. Your PS could only run 2 3 diode series strings in parallel and you will max out the 2A ps..
The resistors function is to drop the 12v to 10.5V....which is the voltage that creates the 1000mA "draw"..
you will need a 1.5Ohm 1.5W resistor for every 3 LED's and 1A per every "set" of three run in parallel....
Yes by limiting your pulse width (duty cycle) to under full out you can control it.. but not very elegantly..
Illustration:
Figure 2: Internally generated PWM signal and LED current for the application in Figure 1
The amplitude doesn't change (1A).......... only the period.. which is how most of these dimmers work.. Cutting into the cycle
The V(dim) is just the signal.. not the drive current or voltage..
without knowing your exact "dimmer" and its inner workings I can't 100% guarantee the above is correct.. but I'm fairly confident that this is how it works..
Overloading the ps is a way to control the current..
regarding "deep red" and using Luxeons as an example:
Are you going to hang the light fixture so it can be raised and lowered? If you do, you will probably want optics on the LEDs so you won't get so much spillover light as you raise them. However, that also reduces how much dimmer the light is when raised. You could also use a "lamp shade" over the heatsink, so it would stop the spillover light from blinding anyone looking at the tank.
Are you going to hang the light fixture so it can be raised and lowered? If you do, you will probably want optics on the LEDs so you won't get so much spillover light as you raise them. However, that also reduces how much dimmer the light is when raised. You could also use a "lamp shade" over the heatsink, so it would stop the spillover light from blinding anyone looking at the tank.
your missing a minor point. The "dimmer" doesn't change current.. it only pulses it. It may average to 700mA but it is feeding all it can to the LEd's...
I wasn't sure on how those drivers work... so they have a PWM output from 0 to Vmax (12 V in this case). That would explain the pretty linear V/A output (from my point of view, measured with a multimeter).
Well, I assume for now, if I keep everything at decent levels it should be ok, until I get some decent drivers.
Is that calculator you used an online application? If yes, and if it's free, could I have the link? Thanks.
Jeff, I have a question: if I buy a Meanwell driver, or other reputable dimmable driver, is the output going to be a PWM, or linear? I thought I might ask, since you know quite a few things about these drivers.
Very few are "linear"... most output a pulsed drive current..
Your major choice is in the type of "signal".. PWM, 10V or potentiometer..
That will determine (or vice versa) what controller you will use..
People often confuse input w/ output..
A good "primer' on what I'm getting at:
It seems to make sense to dim light by pulsing max amp and not by lowering the amp value in order to prevent colour shift associated with running LED at different current.
Probably the disappointment for some will come from the fact that actually the led is at full power, drawing MAX amps (1A if Meanwell LDD-1000H / XPPOWER LDU5660S1000) during the ON time instead of operating at a lower current, which I believe was one of the important things.
i run similar diy light so ill commen if thats ok.
1) spectrum. youre on right track looking at spectrums, but RGB will get you nowhere. i asume you alredy figured that out from graphs. ive done several color layouts, including RGB ofcourse. and came down to what i have today and am very pleased with it. cool white x12, deep red x3, cyan x2. that pretty much cover the spectrum also 'on paper', and from calculation generats over 80 CRI.
2) the biasing. when led heats up durin operation, its voltage drop increases reducing voltage on bias resistor, wich obviously decreases current. the less voltage you are leaving for resistor the more heating will affect current. that is why a good tone is being considered leaving at least 20-25% voltage drop on resistor. this is hard obtainable using 12V, but the good news is you dont have to. 15V, 18V, 24V PSUs are on evilbuy for cheap. PWM dimmers dont actualy care for voltage sou youre fine there also. evilbuy PWM RF dimmers are rated 5-24V btw. oh also voltage drop changes from current, so you cant just use typical voltages from led datasheet. you need to look at I/U graph and measure actrual voltage on resistor afterwards and tune its resistance. believe me you will need to tune that once its built.
3) efficiency. if you look at led efficiency graph from datasheet you clearly see, the cooler it runs, the more effective. this is why you dont want to use rated current. if youre talking so called 3W chineese leds, you dont want to run more than 500mA through them, wich makes them 1.5W (~3Vx0.5A). btw i stongly suggest you go for cree or similar brand low voltage drop leds. use as little chineese as you can, they have crappy heat dissipation.
and sorry for my inglish lol
and to add a bit oil in fire, dimmers are for weak ppl who cant get it right from the first time tune your setup like a real olschool man - using series resistances you have there. chuck norris dont have dimmers D
I'm making a similar custom design for an Edge 6gal, with aluminum channel that will be filled with a strip of ~22 LEDs (5630's). The strip is 6500k, but I also have red 630nm, blue 465nm, and white 3500k LEDs I can swap in for any one of them (I can solder well, and calculating new resistor values for the red/blue sections is easy).
But from what I read in this thread, it's possible to get a "good" spectrum from purely Warm and Cool white mixed? If red/cyan(or blue) don't give a large impact to plant growth in a freshwater aquarium, that makes this custom setup a lot easier with just WW + CW (~3000k and 5000k).
This has been a great read, thanks again for all the valuable information. Cheers! :icon_smil
The ease of dimming and its relatively cheap cost, ramping, and programming not to mention changing it's K value on the fly is one of the MAIN strengths of LED's compared to fluorescent technology..
Wow, a whole ton more great information. It seems like 660nm/6500k will be the 'sweet spot' for me, providing both good lighting for plant growth, and and easy/inexpensive build (under $30 including aluminum track/heatsink for a 16" light) with plenty of leftover parts.
6500k strips are easy to come by, the 660nm red LED's took a bit of searching, seems a lot easier to get 620-630nm at low cost. Thanks again!
I'll likely be replicating the 660nm/6500k setup jeffkrol showed above. Great site too btw, just not going to spend $125+ on that setup
I am a fan of even distribution of light. That being said, I would group the colored leds in clusters, somewhat towards the corners of the heatsink, not in the center... something like this:
I would split this into 5 lines if possible, keep the leds about 1 inch apart. As colored leds are closer, the color mix would be better, and you will see less colored bands/spots in the tank.
I would even go and move the two "warm" ones from line 3 to line 4, between the cool leds - this way you will have a bit more light in the front of the tank, where I presume the plants are lower and need more light.
Advice: take into consideration using or upgrading to dimmable controls - I believe you will find it useful, as you might what to change the color tint or reduce red/blue illumination to prevent algae.
blue overkill, red shortage is what i see.
keep in mind that every white led also is a royal blue one(see spectrum in datasheet)
and to make things worse, red light is absorbed in water at a much higher rate than blue
1. Keep in mind there are only 4 cool whites, the rest of them are warm whites, 3000k, pretty yellowish. Even so, comparing the final composite with the initial charts, the ratio has not been kept. In the charts, indeed, there's a spike of blue. In the final layout you have 4 blue/2 cyan - so the blue spike would be huge compared to the spectrum charts.
2. That's exactly why I suggested dimmers... at least on the blue/cyan channel(s)
3. It would not be good to combine leds of different voltages on the same channel, I would be careful with the controller for the red leds, as they tend to run around 2.5-2.8V. They should be on a single channel. I would use more of them (maybe 4), spread them around, on one channel. It's easier to find a supply in that range (about 10-11 V, constant current).
Here's my build (drilling/tapping the damn heatsink was a pain in the butt ):
Wow, that's quite the lighting rig you have there. Do notice any blue "spotlight" effect right under the blue LED?
On a side note, does anyone know where to find 5630 SMD LEDs @ 660nm? Everywhere I look its 620-630nm. Looking for 5630 to replace some CW LED's in a strip.
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