DIY LEDs - The write-up

[der_wille_zur_macht]

Pretty awesome. The first build I have seen that really takes advantage of individually aiming single LEDs.

Speaking of, I would throw a PAR meter under that rig if I were you. With that many LEDs essentially "concentrated" towards the same general area of the tank, you might be getting a lot more light than it looks like - especially with optics. I've repeated this example a bunch of times in here but again I will reference my experimental build on my 60g tank, where I essentially fried a bunch of high-light SPS by aiming a very small number of LEDs right at them.

 

[Taqpol]

Fishman, I haven't been paying too much attention to the LED forums, but I popped in today and your build was the first picture I saw. Holy crap, that is the slickest most professional looking DIY fixture I think I've ever seen!

I do agree with DWZM though, you might be focusing a lot of light on a single area. I have been having a lot of trouble with my tank, most of it non-LED related, but I really think that my 60 degree optics, 14" height, and high intensity caused a lot of coral bleaching. I am also of the opinion that something about focused LED light might effect the way PAR meters read the light (The sensor can't pick up all the light because of the angle, so it posts a lower PAR number then what the coral actually sees?) but I have no way to prove that. Regardless, for my build I might switch entirely to 80 degree optics.

Also note that because of the angle you will get a lot of light reflected off the top of the water, which for me resulted in a significant decrease in PAR at the far ends of the tank where I had my fixtures angled. Of course, you might also get better growth patterns with more angled light.

 

[The Grim Reefer]

Has anyone actually taken PAR readings with and without optics?

 

[CJO]

Has anyone actually taken PAR readings with and without optics?

I have. I don't have them in front of me, but 60 degree optics made a huge difference from no optics at all. IIRC, it was about a 100% (2x) difference.

CJ

 

[der_wille_zur_macht]

I am also of the opinion that something about focused LED light might effect the way PAR meters read the light (The sensor can't pick up all the light because of the angle, so it posts a lower PAR number then what the coral actually sees?) but I have no way to prove that. Regardless, for my build I might switch entirely to 80 degree optics.

I agree - corals in LED-lit tanks seem to often respond as if they're under more intense light than a PAR meter indicates.

Grim, at least a few people have done good comparative work with and without optics, but there are so many factors involved that IMHO you have to take each case one by one. There was a user who posted a build in the regular reef forum a number of months ago who did a good job - I think his username was santoki or something like that.

 

[TheFishMan65]

I must have been a bad boy - Santa did not bring me a par meter Right now I only have 1/3 with lenses and every seems fine (3 days). May have to see about borrowing the club meter. Thanks for the advice.

Grim - yes, but I can't rememberthe thread. I must like you try:
http://www.reefcentral.com/forums/showthread.php?t=1902716
http://www.reefcentral.com/forums/showthread.php?t=1761942
Seems like there was another one, but I can't locate it.

 

[kcress]

It was lacking around here. Good to see you back Fish.

And yes DFason don't be a turkey..:hmm3: Tell us what got your rig working so we can all benefit.

 

[The Grim Reefer]

WHat I meant was Actual PAR readings in a tank full of water, My bad. Light striking water in a direct line penetrates the water much more than light hitting at an angle which allows more of the light to reflect off the surface. I suspect in the case of 60 degree optics the real world gains are going to be crazy. Might have to order up some optics and play.

 

[der_wille_zur_macht]

Agreed 100% Grim - several of the people posting PAR results have taken the measurements in a manner where I feel they are not very meaningful. IIRC Santoki did his over a tank with water in it, and compared different optics. Here's his thread. I don't have the time to dig through it now but I remember his numbers seeming reliable:

http://www.reefcentral.com/forums/showthread.php?t=1761942

 

[The Grim Reefer]

Thanks for the link Willie

Don't have time to look right now but it looks like his first batch of readings were a comparison to wet and dry readings rather than wet with vs wet without optics. I'll dig deeper later.

 

[RCBrooke]

Has anyone had / noticed a light pulse after turning a meanwell driver (ELN-60-48D) off?

I finished the 3rd 12x string last night. 1st string is 12 xp-e royal blues, 2nd string is 12 xp-g (6nw/6cw),
and the third string is 12 xp-e royal blues. This last string comes on fine, dims OK, but right close to 7 seconds after I turn the power off I get a light pulse. The other two strings didn't pulse when I tested them. I checked and found no shorts to the heat.

Any thoughts?

Thanks,
Randy

 

[wld1783]

Has anyone actually taken PAR readings with and without optics?

LED Optics Test

The test fixture is a 24" LED Strip Kit custom assembled for Corbins Exotic Pets Pets in Buffalo Grove Illinois.

The Heatsink is a 24" x 8.46" from HeatsinkUSA. The LED strips are 6 XR-E Royal Blue/White and 4 XRE Royal Blue. The drivers are MeanWell 60-48D. The four Royal Blue strips are driven at full power (at 9 volts appx 580mA) in 2 parallel series of 12 LEDs. The other Royal Blue/White Strips are driven by a single MeanWell 60-48D adjusted to 750mA at 9Vdc

The drivers were adjusted and the input voltage was provided by a Radio Shack Enercell. Par was measured 24" above the fixture center mass and 24" centered but 12 "œ to the side. The meter was an Quantum Flux Apogee meter MQ-200. Watts were measured with the common KillaWatt meter.

No Optics

Driver Input........PAR@24"........PAR@24"........Watts
Volts DC..........Center Mass....Center + 12"

9........................214................142... ...........186
7.5.....................180................128.... ..........162
6........................155................100... ...........124
4.5.....................104.................82.... ...........84
3........................78..................58... ............49
1.5.....................32...................22... ............21

60 Degree Optics

Driver Input........PAR@24"........ PAR@24"........ Watts
Volts DC...........Center Mass.....Center + 12"

9........................355................150... ............186
7.5.....................310................131.... ............162
6........................242................78.... .............124
4.5.....................202................66..... .............84
3........................131................43.... ..............49
1.5......................60.................18.... ..............21

70 Degree Optics

Driver Input........PAR@24"........PAR@24"........Watts
Volts DC...........Center Mass...Center + 12"

9........................432...............170.... ............186
7.5.....................348...............158..... ...........162
6........................301...............140.... ............124
4.5.....................262...............95...... ............84
3........................171...............65..... .............49
1.5.....................74.................30..... .............21

80 Degree Optics

Driver Input........PAR@24"........PAR@24"........Watts
Volts DC..........Center Mass....Center + 12"

9.......................330................183.... ............186
7.5....................292................174..... ...........162
6.......................254................143.... ............124
4.5....................190................109..... ...........84
3.......................125................53..... ............49
1.5....................56..................33..... ............21

 

[wld1783]

Has anyone had / noticed a light pulse after turning a meanwell driver (ELN-60-48D) off?

I finished the 3rd 12x string last night. 1st string is 12 xp-e royal blues, 2nd string is 12 xp-g (6nw/6cw),
and the third string is 12 xp-e royal blues. This last string comes on fine, dims OK, but right close to 7 seconds after I turn the power off I get a light pulse. The other two strings didn't pulse when I tested them. I checked and found no shorts to the heat.

Any thoughts?

Thanks,
Randy

I've had that on a couple...a single blink when the power strip is turned off. Once put on an APEX there was no blink.

One thing to note if your forward voltage does not match the driver it makes a nice christmas tree light by blinking regularly.

Make sure you check the mA of the 48D and adjust the output. I measured one at 1.8A :strange:

Bill

 

[wfournier]

LED Optics Test

The test fixture is a 24" LED Strip Kit custom assembled for Corbins Exotic Pets Pets in Buffalo Grove Illinois.

The Heatsink is a 24" x 8.46" from HeatsinkUSA. The LED strips are 6 XR-E Royal Blue/White and 4 XRE Royal Blue. The drivers are MeanWell 60-48D. The four Royal Blue strips are driven at full power (at 9 volts appx 580mA) in 2 parallel series of 12 LEDs. The other Royal Blue/White Strips are driven by a single MeanWell 60-48D adjusted to 750mA at 9Vdc

What brand optics were used? It looks like the 70° is the winner to me.

 

[RCBrooke]

LOL.... When typing the post ya think ya put in all the details......!

The menawell's for the blue's are at 800 ma by digital multimeter and 1000 ma for the white string. With a 2:1 ratio I thought the blue should be run a bit higher than 700 ma and I picked the 1000 ma setting just for the nice even number (I'll drop it downward if I want a more blueish look).

Also I was testing one string of LED at a time. In the time since I posted, I've rewired so that all strings are on at once. NO Flash after turning off. So I guess I'm OK. I'd still like to know what causes it though.

Now that I've a decent camera I've really got to learn how to add pictures.

Thanks,
Randy

 

[sammy113]

Need some input on this little rig. Lets say I have Royal Blues and some True Violets on a meanwell ELN 60-48D driven at 1000mA. The True Violets has a max of 500mA. If I do this is ok? All LEDs in series but the true violets in parallel hoping to reduce mA down to 500

 

[TheFishMan65]

In theory it will work. Ideally you would want a fuse. If one of the violets open all the current will go through the other and it will blow. Also if the Vf don't match you may get 450 and 550 so maybe only run at 900ma total (or 3 in parallel - if one goes two are still in parallel and don't go bye-bye).

 

[Foxy Brown]

Just a quick note on some of the driver issues and finding cheap ways to do it. This is specifically to address (or just add to) kcress's post from about 20 pages back... sorry it's a bit of a necro.

There is an adjustable regulator which can be had for about $1.00 called LM317. This has 3 pins IN, OUT, and ADJ (adjust) and can run over 30 volts at 1.5 amps. This is perfect for driving those 6-LED strings at 24V. You simply wire a 1.25 OHM resistor to the OUT line, and then the LED after this. The ADJ line is tied between the resistor (just after it) and the first LED. This gives you a 1amp CURRENT controlled regulator. Double to resistance, and you halve the current... easy math. You can then look at potentiometers instead of resistors for fine control.

The advantage here is that you should really have a current controlled driver, and the I-V relationship in LEDs is highly nonlinear. A small change in voltage makes a very large change in current which can quickly run away and kill the LED. The second thing.. a blown LED (short) will cause an increased current flow in a voltage controlled source, and could blow the rest of the string. Better than a fuse, this source will still drive only 1A, even if 2 blow. A simple resistor will start running the remaining LEDs too hot in this case, and may take them out too. The driver basically acts a resistor that changes is resistance to makes sure that the resistor always has a 1.25V drop across it which is 1A for 1.25 Ohms, and therefore the LED string will always run a 1A... This also lets you reduce the power dissipation of the resistor (1.25V x 1A = 1.25W). The LM317 also has internal current limiting and temperature sensing, so it will shut itself off before it fails in case anything goes wrong. This makes the circuit more fail-safe and even cheaper.

Another idea for those trying to make dimming circuits is to use PWM. This essentially turns power on and off rapidly, giving the effect of dimming. This can be done very easily using a micro-controller and a power MOSFET. The MOSFET (520N for instance) can typically handle 10A, more than enough and is again $1-2... but what if you don't have a microcontroller? There's another simple and cheap circuit you can use.

The idea is a little more complex, but still easy to do at home. The well-known 555 timer can be used to generate a "sawtooth" wave, basically a triangle wave instead of square or sine waves. That output is fed to one side of a comparator, which simply a switch than turns its output on and off based on which of 2 signals is larger. The other side of this comparator gets hooked to the center tap of say a 10k potentiometer which is wired to the supply and ground. The output of the comparator is the finally hooked to the gate of the MOSFET. Lets say we set the potentiometer half-way up. The triangle wave will then spend half its time below that voltage and half above it. The means that the comparator, and therefore the MOSFET will spend half its time on and half its time off, which leads to 50% output on the LEDs. This gives two big advantages... The first is that for those using white LEDs or various different colors of LEDs, the color drifts ALOT less when using PWM dimming... and yes color does depend on the output due to a different temperature of the LED. The second is that the same triangle wave can be fed to any number of comparators, and you can get up to 4 or even 8 comparators on 1 IC, which means very little additional investment to control multiple colors and/or channels.

I've attached a sample circuit diagram for the sawtooth oscillator for you, but triangle waves work equally well. The frequency is almost unimportant for this application, something between 100Hz and 10kHz will be fine, so component selection is simple. For the comparator an LM339 is both cheap and effective.

For a total price of around $20 you can build a 4-channel control system and driver sets for almost as many LEDs as you could possibly want to run (plus the price of the 24V power supply) and have flexibility and fail-safety. A little more complicated the kcress's design but still easy, even cheaper and a makes me feel a bit more secure. You may not want to tackle PWM, but I high recommend you try a real current-limited supply instead of a simple resistor, its only 1 extra part.

 

[wld1783]

What brand optics were used? It looks like the 70° is the winner to me.

DIA.20-CREE-70

Wish I could give more info.

Bill

 

[TheFishMan65]

Foxy, not sure what you are geting at. But have you read the DIY driver thread? For About $1.50 you get the LM37 functionality and PWM that you described above. All you need is a sense resistor (ok the math is not as simple) and a couple capacitors. Still need the 24v supply.