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DIY LED Questions Answered Here

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Guest thefishman65

I enjoyed doing a presentation at yesterdays frag fast. It seemed there where more questions about LEDs than about how to solder them. So for those that didn't get an answer, forgot the answer, didn't get to ask there question, or any reason you like (you were more interested in frags :)). Here is your chance to ask them.

 

I follow several LED threads on reef central and had composed a summary of some of the information there. Hopefully the formats are pretty much the same (they seem to be) and the copy and paste will work, So give me a few minute to get the next three posts in and then start asking away.

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Guest thefishman65

I have read this thread and several others. I will try and summarize, because there is a lot of reading and a lot of repeated questions. Please realize a lot of this is from memory and my opinions so it could be wrong. As this goes on I am posting more and more quotes. I tried to get the original post; this means that you can click the blue greater than symbol and view the original post and then the post around it if you need additional information.

 

And thank you to all of the people (too numerous to count) that have supplied this information. I have added some information form notes that CJO took. I am sorry, but I do not know if they are direct quotes or just notes. I am not trying to plagiarize.

 

So I can keep track of it this is version 2.2

These are some only seminars that if you really want to know more might help. Thank Electronic Design and Digi-Key and a bunch of companies.

INFORMATION COLLECTED FROM HERE (and probably some others)

So if you are still interested in doing LEDs I recommend looking at them as well:

Related threads that might be useful:

There are numerous other threads relating to builds, but I think these cover most of it. If you think I missed an important thread (highly possible there are a lot of threads out there), please let me know.

 

LED Specs

Cree XR-E Royal Blue

Color: Royal Blue

Dominant Wavelength Range (nm): 450 – 465

Max Current (ma): 1000

Viewing Angle (°): 100

Standard Min. Flux @ 350 ma: 425 mw, 350 mw

 

Cree XP-G Cool White

White: Cool

CCT (K): 8,300 – 5,000

Max Current (mA): 1500

Viewing Angle (°): 125

Standard Min. Flux @ 350 ma: 139 lm, 130 lm, 122 lm, 114 lm

 

WHERE TO GET THE STUFF

Here are the most common location where people are getting supplies.

LEDs

  • Rapid LED
  • LED Supply
  • ETG Tech I find this site confusing so you may have to contact anna@etgtech.com. Also last time I checked the minimum order was $75, which is doable with a 12 LED configuration with lenses.
  • Deal Extreme The cheapest place for Cool White Q5 XR-E (~$4.50), but slow to ship.
  • Cutter They are out of Australia, good prices. I have read they are slow to ship, and at one point had real hard time getting you what you ordered.

 

Power Supplies

 

TOOLS

You will need the following tools (and some others probably) to complete this project.

Soldering Iron

Most of the recommendation is for a 40 watt. There was a nice discussion in one of the threads. If I could just remember where I would quote it. A post by der_wille_zur_macht says 40-50 watts.

How to Solder a Star

In the LED thread I detailed proper soldering technique. Here's it is lifted in its entirety:

 

Soldering... It's a bit of an art form. It you're an expert you could probably solder the stars with anything but a torch. But if you aren't accomplished a 'just right' soldering iron is required. Something around 25 to 40watts. The biggest problem would be one too small as then you damage what you are soldering by sitting there with the heat on, waiting, and waiting for the solder temperature to be reached. Meanwhile the device is being roasted.

 

You need "rosin core solder." Make absolutely sure it's not 'ACID' core solder. Acid core is solder for soldering radiators and copper pipe. The acid remains and will dissolve your electronics in short order. No-core or plain solder is also very bad as there is no cleaning action which is vital to an acceptable solder joint.

 

You want lead solder too - NOT "lead free".

 

Let your iron heat up fully. Then wet it with your rosin core solder until it's blobbed up in a wad. This lets the rosin act on the tip to clean it. Wipe this blob off on a moist sponge,(not sopping wet, just barely damp). If you have no sponge use a damp folded up paper towel.

 

Wipe with a very fast twirling dragging motion as you are trying to clear all the solder off the tip before you cool the tip to the point that the solder freezes again.

 

Apply a weee bit of solder to the tip and then immediately apply the tip to the star's pad. As soon as you apply the tip to the pad take your solder and touch it to the exact point where the tip meets the pad. You are trying to maximize heat transfer from the tip to the pad. You do this by filling all the voids with a molten metal thermal bridge. Pause for, perhaps, one or two seconds move the solder to a distant place on the pad and hold it there. When the pad heats up enough to melt the solder feed the solder in at a good clip until the pad has a large mound of solder on it.

 

Do the same thing to your wire if it is un-tinned. (actually do this before you do the pad!) Better(superior) would be to use only pre-tinned wire in the first place.

 

Now once you have your mound of solder on the star pad bring over your wire, hold it on the Star's pad. Place the tip on top of the wire. You want to reheat the pad thru the wire. When the wire sinks into the blob hold the position and watch the blob. You want the entire blob to melt again. The instant the blob has remelted remove the tip while holding the wire EXACTLY where it is. No wiggling allowed! Coffee shakes need not apply. Once the solder has refrozen move on to the next connection.

 

 

Hi hllywd.

Pre-tinning has its place but.. The physics of soldering are kind of complex. When you pre-tin you leave a layer of already heated flux on all the various surfaces. This can cause subsequent soldering to be sub-par. Also using the 'heat up the two and just melt them together' method means you get almost no flux action on this second solder-less heating.

 

If you ever watch the flux action under a microscope you will see the flux push everything foreign away allowing only the two items to be connected with solder. When you use the tack them together method none of this happens.

 

In most cases for our LED fixtures it's still good enough. But I would rather not. I realize that to do it the right way you need three hands. :rolleyes: I have one of those little stands with alligator clips sticking off of it. I just grab the wire with one of them and have it hold the wire to the pad. Then I can show up with the iron and the solder.

 

Jay1982; You would want to re-heat that joint. You always want a hot solder joint, not a cold solder joint. 'Bulbous' is often a sign of a cold solder joint. The other sign is a dull un-shiny result.

 

This thread has a lot of information on soldering

Soldering Technique

 

Multi Meter

You will need to be able to measure voltage, current and you will probably want resistance. Almost all meters have these so it should not be a problem. However, when measuring current you will need a meter that goes to at least 1 amp I would recommend 10 amp.

 

And a few tips from kcress:

You can change the settings with the driver on. Be very careful you touch nothing when that driver is plugged in. Anything could be live, like those pieces of metal.

 

On your meter, if you change things over to current measure absolutely always power down. Remember if you interrupt the chain while the driver is powered - you will fry the chain.

 

Also, always unplug the meter current lead from the meter and replug it into the voltage position IMMEDIATELY when done measuring current. Not doing that will surly result in you picking up the probes and trying to measure a voltage while the meter is in current mode. Result - blown meter.

 

LEDs

Which LED

The whole reason most of got into this light scheme was for efficiency. Having said that there have been a lot of question like will this LED work. The thing to look for is efficiency and spectrum. If the spectrum is what you want (matches the bulbs in there now) then you are fine. Most people have picked the CREE led because of its efficiency of over 100 lumen per watt. If the LED you are looking at is not over 100 lumens per watt you probably don’t want it.

 

How Many

The current recommendation is 1 LED for every 10-20 square inches of tank surface. Fish only could get by with the lower count, and a coral tank would need to be near the higher end. However if you take advantage of LEDs ability to focus corals could be spot lighted and cut down on the number of LEDs required.

 

Spacing

Currently the general recommendation is 2 to 3 inches between LEDs.

 

Color Mix

Currently the general recommendation is:

  • 50/50 for white XR-E and royal blue XR-E
  • 40/60 for white XP-G and royal blue XR-E

If I remember correctly this is 14k. If you want a bluer tank you more royal blue. Before you ask, there is no XP-G in royal blue.

 

Ultra Violet LEDs

It is believed that UV LEDs are not needed. But if you do here is a source that hlsooner found: UV LED

 

Forward Voltage

This always comes up and I found this real nice post that was talking about meanwells, but applies in general.

... In the datasheet for each respective LED, there's a V/I curve that lets you look up the voltage the LED will drop at a specific current. With this information in hand, you can calculate the voltage expected across a certain number of LEDs in series.

 

The numbers do vary a bit from model to model and even color to color, so it's important to look up the actual figure if you're interested in doing the math. And of course, clearly, it varies as the current varies.

 

Plus, there is a fair amount of variation from LED to LED, around the number quoted in the datasheet. So, LED XYZ might be quoted at 3.5v at your desired current, but you might find some that drop 3.55 or 3.48 or whatever. So, it's important to leave a margin of safety when planning how many LEDs can be run on a given driver.

 

In most cases, with the 48v meanwell drivers, you can just assume 12 LEDs and be safe. But if you're using some of the lower-drop LEDs (i.e. the XP-G or Rebels) and lower currents, and you want to really load things up, you might be able to get away with 13 or even 14 per string.

 

POWER SUPPLIES

If you are doing a really big fixture multiple power supplies can be a problem. See this post by kcress:

[*]Summary of multiple power supply issues)

 

SPLASH GUARD

I think the recommendation is anything less than two feet should have a splash shield to keep the spray away from the LEDs.

 

Wire

To quote der_wille_zur_macht, “Wire gauge between LEDs should be 20 - 26 gauge, pretinned, with good insulation.”

 

Kcress found a great place for wire:

Stranded wire

 

HEAT SINK

Types

True aluminum heat sink. Most have used this so far but it is expensive and heavy. The advantage is that will a fan to get good air flow you won’t have to worry about heat.

People are beginning to experiment with some the the aluminum channel found at local hardware store. Not a lot of reports, but I have not heard anything bad. The advantage are that is lighter and cheaper. I also think it would work better for convection cooling. If air can rise through your fixture with smaller pieces of aluminum you should get fewer areas where air flow is limited – also yet to be proven.

 

Mounting

There are three main mounting options (that I can remember).

  • Screw and thermal paste
    Screw make for the easiest changes later, but a lot of time to drill and tap. I personally did the screw method, but did not tap. If you follow me lead DO NOT tap with the same screw twice – the head will twist off. Oh what fun :).
  • Thermal Adhesive pads
    These may be hard to take off. Some have done it, but it was early and the longer they sit and the hotter they get The better they sick if I remember correctly.
  • Thermal epoxy
    To the OP: I just spoke with a rep at Arctic Silver about their Arctic Alumnia thermal adhesive. If you use this product, its on for life. He said its basically made with the same compounds as used in cement and if someone were to try and remove an LED from the heatsink that the LED itself would fragment apart before the adhesive gives way.

 

How hot is too hot

Kcress said this very clearly:

If you can keep your finger on it you're OK.

 

And I mean the bulk area of the heat sink not the edge of a fin. :rolleyes:

 

Heatsink Size

CJO found this information and I think he got it from lynxvs.

I've posted this before I think but it might be helpful. I use just a flat plate of aluminum as my heat sink. I did some calculations below to justify heat sink size. I attach a PCB directly to the plate using screws.

 

Max Junction Temp = 150° C

Power of Single LED = 3.4 Forward Voltage X 700 mA = 2.38 W

Ambient Temp = 70° C ( A SWAG)

Thermal Resistance between Junction – Case (From Data Sheet) = 10° C/W

Thermal Resistance between Junction and PCB (From Rebel application note) = 7° C/W

Total Thermal Resistance = 10 + 7 = 17° C/W

Total Thermal Resistance between Junction and ambient air = (150 – 70)/ 2.38 = 33.61 ° C/W

Thermal resistance between Case and Ambient air = 33.61 – 17 = 16.61 ° C/W

 

The amount of heat dissipation that can be achieved with a flat plate of aluminum is indicated below.

 

---see attached diagram---

 

Using a 3mm plate looks about 20 cm^2 per LED converting to inches is equal to 3.1 in^2 * 50 LEDs = 155 in^2 The plate I am using is 24 X 7.25 = 174 in^2 not sure if you can count both sides of plate as surface area… I also have two cooling fans to help

Edited by thefishman65

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DRIVERS

There are two main type of drivers. I did not use either one so I did not pay a whole lot of attention to these. But before we get there, there has been discussion about running string that involved terms like series, parallel, matrix, and others (thanks CJO for reminding me about this fine kettle of fish :)). Generally it is agreed that each driver should drive one string as kcress says (I think this was all him):

You should only have one driver for each string. Period.

 

Any other scheme risks all the LEDs as soon as one fails shorted.

 

Two stings in parallel will toast them all. Why?

 

If you are running two stings in parallel and each string is, for example, 700mA, your driver would need to put out 1400mA. Now if one LED shorts the driver will continue to drive 1400mA into the two stings. But the string with the shorted LED will have a different voltage requirement than the good remaining string. This causes what is termed as "current hogging". The good sting will either go dim or OFF completely while the bad string may have 1200mA running thru it. The remaining LEDS will fail in seconds.

 

Once the entire string with a short in it has blown or one of the LEDs fails OPEN the driver will then focus on driving the 1400mA thru the remaining good string. Every LED in that string will also fail within seconds in a domino effect.

 

One driver per string!

OK, CJO was really interested in this and has a good reason, I don't recommend (and I think most will agree) this, but if you really want more information check the bottom for some notes CJO collected.

 

Meanwell

These are nice because the run off of 120 so no extra power supply is needed. There are several different type. The differences (I think) are how much power they can supply and how they are dimmed. This thread seems to answer a lot of questions: How to dim a Meanwell ELN-60-48D...

D Version

I have seen several question on wiring so since Stugray said it so clearly:

The AC wires that go into a plug don

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Guest thefishman65

I should probably qualify that I am no expert. I understand the principles involved and will do my best to find answers. Enjoy!

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Thank you very much for the information and the presentation, I enjoyed it very much!!

 

I have been following LEDs with interest for a while, but am hanging on to MHs for the time being until more experience is gained with them. Like you mentioned in your talk, there is not much in the red/yellow portion of the spectrum. So I will let some more time pass before I take the leap into the LED realm.

 

I cant add anything to your LED discussion, but I can solder... So I have one small thing to add there, I recommend using a 63/37 ratio lead/tin solder, especially for someone who is more inexperienced with soldering... this mixture has a liquid/solid point, instead of a plastic region that transitions between the liquid and solid. It means that after the solder melts and wets the area you are soldering and heat is removed it will solidify almost instantly. Two benefits, first better wetting action onto the components, and less chances for a fracture of other defect to appear while the solder is cooling.

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I may have said it poorly. LEDs come in what ever spectrum you you want. Mose people like the look of a mixture of cool white and royal blue. But some people use warm white red and yellow LEDs are also available. However, I think I red somewhere the red light may be bad for corals. Maybe someone with more coral experience will chime it.

 

The tends to by the type of solder recommended in most of the reading I have done (or 60/40 not much difference maybe only rounding). With the addition that it needs to be a rosin core solder. The rosin acts a cleaner and helps spread the solder - I think.

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Rosin is a reduction agent that cleans and "pushes" contaminants to the surface of the solder so they can be easily cleaned off and allows for better adhesion between components. Using rosin is necessary and using a rosin core is the easiest way to do it (and what I use/recommend), but not the only way. You can brush it on separately as well, which results in wonderful solders, but one heck of a mess to clean up. Either way, the rosin needs to be cleaned off when complete since it is somewhat corrosive and can lead to long-term performance issues.

 

60/40 also works, but has a couple degree plastic transition region between liquid and solid states (i.e., a couple of seconds) where the 63/37 transition happens almost instantly at a single point with no plastic stats. Moving one of the two component during this time often leads to fractures in the solder joint (more resistance therefore more heat).

 

Of course, if you are clamping everything and soldering on a bench, it will likely not make any difference which solder to use, otherwise there is a couple of seconds where things need to be held perfectly still while the solder solidifies... hard to do IME.

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wow thank you so much for assembling this thread! something i didnt see and didnt get a chance to ask (i could have missed it as im reading on a mobile) and i might know this if i was a little more astute in electrical engineering but is there any risk of significant amperage drop in haveing say a 5-6' foot run of wire between my power source?

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Guest thefishman65

There are charts for this, but a heavier wire will also help solve this problem. I would need to find a chart (not my area of expertise), but I think a 20 gauge wire would probably be fine. Worst case cut a cheap extension cord it is probably 14 or 16. So yes it can be overcome. I will help you figure out (as best I can) what you need if I can get all the information (drivers, leds, current, etc.).

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Fishman-

 

Eric from GBD tested your build with his par meter yesterday and at 3' away in open air, it was reading in the 300's.

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zygo can you please post pictures of the build? I'd love to know the specs also on this build.

 

 

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Guest thefishman65

Do you know if that was with the lenses? For those that don't know it was 6 Cree XP-G (no lenses) and 6 Cree Royal Blue XR-E (maybe 60 degree lenses) running at 700 ma. For those that really care this was the kit.

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Do you know if that was with the lenses? For those that don't know it was 6 Cree XP-G (no lenses) and 6 Cree Royal Blue XR-E (maybe 60 degree lenses) running at 700 ma. For those that really care this was the kit.

 

 

What hood did you use? Do you have a link to that as well?

Thanks!

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Guest thefishman65

I had gotten the heatsinks from a metal recycler - bought them off someone bringing them in. The hood was a scrap from the office. So, sorry no links.

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Now that I'm on a lap to with a 17" it is much easier to read, if you're up my way contact me I'll give you some frags you've saved me a ton of time and headache :clap:

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fishman-

 

I'd like to build another just like the one I won. If I just copy it and solder it, will it work correctly? I mean, do I really need a meter?

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Yes, I believe that if you bought the same kit and kept the spacing the same, and the angle (I tried to make hte heatsinks parallel, but I don't remember if they are) then it should give the closesame par reading. I have not made enough to know for sure. Every LED is a little different; even in the same bin. Put sinmply I would expect very similiar results if you bought the same kit.

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With dimming drivers how do you create a sunrise / sunset light cycle? Is there a specific controller?

 

Yes, its called the Ardiuno controller, and that throws a whole new set of issues into the mix

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So I have another question and I've since read this whole page and some corresponding threads. Its commonly assumed that the mean well drivers will run around 12 leds. I'm interested in running say 18-24 leds in a blue white mix, but I'm also interested in running some of the more off beat color ones like the UV, Green, and red LED's. Setting the internal pot adjusts the mAh? being put out from a driver so If I wanted to run say 3 meanwell drivers I could run 1 driver + 12 leds, 1 driver + 12 leds (have them set at around 1000 mAh (what ever is required by the string), and then another 1 driver + 8 leds (mixed colors (UV, Green, Red) and just adjust the internal pot based on the smaller amount of load presented by the lower number of LEDS?

 

 

 

Also for all those checking in on this thread, how many would be interested in a GB on certain things? Please don't clutter up this thread but respond here http://www.wamas.org/forums/topic/38177-interested-in-an-led-gb/

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Guest thefishman65

jason, The arduino is the cheapest way to get dawnto dusk dimming I think. However it my understanding that some if the reef controller out there can support that feature.

 

You have the possibilities correct on how to wire the LEDs and drivers. I will point out that I have found no information no support the need of the different colors. But as glassbox pointed out it can enhance some colors. I also think I read that red light can retard coral growth. I am no expert on corals so all i am trying to say is that you may need to research this.

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When you guys are screwing the LEDs on the heatsink, I would highly recommend you to polish the heatsink with Mothers! It only takes like 15mins-30min of work and it's easy. You can use a cloth and a drill to do the work. Any question on LED built, you can PM me. I will try to answer whatever I know. I have mine running since Feb/March 2010.

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Do I really need a heatsink? Suppose I was to take the stars and mount them to another piece of metal with a delrin or other heat resistant plastic spacer about 1/2" thick. Then I could blow air around the stars for cooling. Will this work?

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I can't say no, because I don't know of anyone that has tried. But I don't think so. From my VERY LIMITED understanding of heat transfer the star does not have enough surface area to dissipate the heat to the air UNLESS the differential is very large (read this as the LEDs are running too hot).

 

Some people are using L channel form home depot and lowes with a fan if you are looking for something cheaper.

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