knna

Before start the mounting tutorial, its a must to talk a little about an esential part of any LED lamp, the Heatsik. This is the part most often missed or wrong sized on DIY LED lamps. I explained in the introduction why keep LEDs cool is esential.

Its not due to heat being a problem for plants, but for themselves. Although the heat is not excessive on absolute units, its created on very small surfaces (high power chips are 1 sq mm). Its a must then extract as faster as possible that heat from the LED. That is what a heatsink does mainly. It may dissipate that heat by air convection directly, or helped by forced cooling.

There are many ways of forced cooling, but always think on them as supplemental for the heatsink, to keep it cooler. Relaying only on the forced cooling is very dangerous, as any failure may damage or destroy the whole LED lamp. It does little sense to rely on a fan or pump to keep safe an expensive LED lamp that should last for years. So you need to install always enough heatsinking that guarantees that, still if you help it with forced cooling, a failure of it not led to permanent damage to LEDs.

A good figure to keep in mind is to use about 50 sq cm (9 sq inches) of anodized aluminium exposed surface for each watt of LED installed. That figure is a minimun. When using forced cooling, that is enough (when running LEDs soft, its possible to use still less heatsinking, but I always advice to try to use as more heatsinking as possible).

If there is no forced colling, its recomended to use about 3x of the minimun, 150 sq cm/W (21 sq inches/W). Its a lot when using just a flat aluminium sheet (although you must count both sides), but not so much when using finned heatsinks.

In order to calculate how much dissipating surface has a finned heatsink, measure its perimeter. For example, say its 25.4cm (10"). Each cm of heatsink has then 24.4 sq cm. Each inch of heatsink, 10 sq inches. So you can install 1W LED at about 2cm (less than 1") one from the next.

On any case, spacing LEDs about 1" (~2.5cm) is a good rule of thumb, as LEDs placed closer heats themselves and cooling them is more difficult (except if there is a very strong forced cooling, forget it).

We have on our grow room more than enough avalaible surface to space LEDs so we can cool them by using just keatsinks, without any forced cooling. I will use this style on the tutorial.

Materials to use for heatsinks: aluminium is what offer the best relationship between price, weight and heat transfer. Anodized one is by far the most adecuate. Copper has still better heat transfer, but its expensive and heavier.

Where to get them?

First option is discarded electronic devices. Recycling rubbish is ecologic and cheap

Shops for electronics carry them, but often prices are abussive.

Aluminium workshops are a great source for them. Windows often uses profiles that may be used to mount LEDs on them. Anything with a flat surface and fins is valid.

Until now, it has been difficult to get large heatsinks. But surely, as LED lighting expands, its going to be shops that sells them. At least, Im going to do it. But its not practical to ship heavy aluminium pieces overseas. I hope other will offer the same in America at good prices (4$ for 1 sq meter of dissipating surface or so).

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lookie_lou

Yeah we're starting!

I'm curious what kind of a heat sink your using? Can you post a picture of it? Also if you have a picture of a finished lamp I'd like to see it it will help me visualize what we're going to build.

Thanks again for starting this thread

lookie_lou

knna

Ok, Im going to upload some pics of the heatsinks I use. But keep in mind there are a lot more shapes and sizes of them:





I use them to do modular lamps: you can attach those bars (3.4cm wide) as you want, to am structure, or hang them the ceiling or walls. At the end Ill post some example of my friend's setups, so you can see how many different configurations you may build with this type of aluminium profiles.

With LEDs installed, ready to work:



Lit on:



And how they lit:

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knna

The most difficult part when building a LED lamp is the Driver. People often concentrates on LEDs themselves, but getting the best of any LED is impossible without a good driver.

The driver is the part that converts the mains AC electricity supply to the DC current needed to run LEDs and that feed them on a controlled way, so they works the best.

So there is two parts here:

-AC to DC conversion

-LED control (current limit or current control).

The driver, technically, is the part that controls the LED. But currently there are many drivers that works directly from mains, so I will call driver to the device (or devices) that accomplish both jobs.

But always is possible to use a Power Supply to convert AC to DC and then an strict driver. There are aswell many drivers that works from 12 or 24VDC power supplies. But they are more intended for applications with only some LEDs, no with lots of them as ours. Good all in one drivers often are more efficients than 2 part ones, apart of simpler to install.

So Ill concentrate on all in one drivers, as usually the offer best perfomance, cost and simplicity, at least for whose that arnt electronically skilled, that surely wont need this tutorial.

But if you want to build your own driver, ask for details at the end of the tutorial

I use some different drivers, depending of LEDs used, but I like this one:



Its as easy to wire as connect the left connector to mains (2 wires) and the LED string to the right connector (2 wires, labeled + and -). On the center, there is a potenciometer (work with a screwdriver) that adjust the current feeded to the string (from 100 to 900mA). It feeds up to a 50V string.

Although there is no many drivers like this on the market yet, each day there is more. Main manufacturers does them, as Phillips and Osram. Power supplies manufacturers have them too. Meanwell has a good range of constant current LED drivers working from mains.

But unfortunately, most of the drivers avalaible arnt adjustable on current. Adjustable drivers are great for our application, as they allows to dim the LED lamps when less light is required, saving watts, and put all the power when its required.

Im designing and distributing high efficiency LED drivers low priced, designed for our application. Adjustable and with wide voltage ranges, valid for large LED strings, that results on lower initial costs and higher power saving during use. Ill put my web page on my profile when avalaible, but if you need something related to LED lighting ask me by PM, I usually have all needed for it. But on other components, there are alternative places where to get them, but drivers thought specifically for grow lamps, there are little to none.

An important note about drivers: you may read on many places that you can control your LED string with resistors. Its possible, but inefficient (wasted power), more difficult that it seems and may destroy your LEDs if you dont do it right. If you wat to build a LED lamps that should last many years, please, forget to use resistors and search for constant current drivers.

Ok, so you now know what you need to know about the three basic parts of a LED lamp: LEDs, Heatsink, Driver. Now you only need to learn how to put them together

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knna

So now you have your LEDs, Heatsinks and Drivers.

Then you need to mount them together:

-Wire. Preferably "solid" (monofilament) wire, at least to connect LEDs. For the conexion between driver and LED modules, standard wire, about 1.5 sq mm of section (sorry, Im not used to AWG) works perfect. 0.5-0.75 sq mm wire is adecuate for 1-3W LEDs (up to 1A).

-Solder and Tin. Optional solder flux. Solder paste is very useful for some types of LEDs (Cree, for example).

-Kapton tape. Its a registered trademark of Dupond, although many brands do it. Its a very thin film of mostly polyamide. Its strongly dielectric (3000V at least required to current go through a 25 microns layer), so we will use it to isolate electrically LEDs and its conections from heatsinks. Anodized aluminium has an external very thin layer of Aluminium Oxide, that is dielectric aswell, but we cant rely on it for full isolation. Kapton tape withstand at least 300ºC, and usually 360ºC and transmits heat decently (but as its a very thin layer, it penalize heat transfer very little). I buy it uften al dealextreme.com, a more than hundred meters roll cost less than 3USD. Of course, special kapton tape from Dupont, with enhanced heat transfer is prefered, but its more expensive too.

-Thermal conductive adhesive. There are many thermal adhesives, divided on two types: two part (usually) epoxy filled with silver or ceramic particles and thermal pads, that are like a paper with adhesive on both sides. Most of them are dielectric, so you can attach LEDs directly to heatsinks with them. But with epoxy ones, I reccomend to be carefull: you need to use as thin layer as posible to minimize the increase on thermal resistance. With LEDs using a metalic thermal slug, that sometimes is not exactly lined with the LED package, going out like 1/4 of mm, epoxy goes to the sides of the slug and it finally gets in direct contact with the aluminium. Its better to isolate the metal slug with kapton before applying the epoxy, or use thermal pads, that although has higher thermal resistance, allows to mount all LEDs homogeneuosly.

-Tweezers. Very useful to manage small pieces, hold on wire while soldering, etc.

-Copper tape. Not strictly required on manual mounting, but useful on any case. A must for some type of LEDs (those than only have electrical conection on the bottom).


Ill use thermal pads (Cooltape, from Dotlight) on this tutorial.

Step 1) Attaching LEDs on position

1a) Mark where are you going to place your LEDs, and the color if using more than one color



I put this pic not only to show that its better to measure LEDs position in order to space them the best way, but because it shows some of the components used on the mounting process: LEDs (Osram Golden Dragon), a roll of kapton tape and scissors, a cut of copper tape (still with the protective pink paper on), the two syringues of Artic Silver Thermal Adhesive on the cardboard used to mix the two parts, and on the upper left corner, some pieces of electrical conection (good if you want to have clean and safe conections).

Marking where a Blue LED is going to be placed:


1b)Putting the kapton tape.

It must be below any part of the LED that is electrically connected. They are usually the electrodes and sometimes, the base of the LED. When using a thermal pad on the bottom, it already isolates it, so most times, you only need to put kapton tape at the lateral of the LED, where leads acting as electrodes shows

So the usual procedure is to put two pieces of kapton paralell, letting between them exactly the space of the body of the LED. Then you attach the thermal pad on that space between the kapton tape pieces:



The best way to place the two pieces of kapton at the right distance, is marking on a small piece of cardboard that distance, so you can copy it to the heatsink fast:



I usually put a piece of kapton first, over the position I marked for the LED, and then I mark the distance where the next kapton piece is going to be placed. If you have problems placing one paralell to the other with a single mark, do two marks at cm one of the next, so you just need to put the upper side of the kapton over the marks

1c)Cut the thermal pad to the desired size, according to the LED. Usually, its the size of the LED itself, except on the case of LEDs with bottom electrical conection, when we should let them free and put copper tape on that area.

As you can see on last post, usually you cut the thermal pad to fill in the space between the two kapton pieces. In this case, the thermal pad is 0.5*0.5mm, which is the size of the Golden Dragon body.

You can see on that pic too that I marked two external marks on it, apart of those of the separation of the kapton pieces. They correspond to where to place the copper tape, exactly where the leads of that LED touch the ground. But using copper tape to solder leads is only optional, not required. It results on a stronger construction, and avoid problems when adhesive fails: it sometimes happen when it gets dirty before attaching. It only happen with thermal pad, which adhesive is softer: two parts epoxies are usually very strong.

1d) Attach LED on position.

Just take it with the tweezers and put it on the adhesive. You can apply some pressure, in order to get a better adhesion, but remember that you never should apply pressure on the lens or the flat silicone window over the chip, as it often damages the LED. Use the tweezers to press over the body of the LED, and not over lens, a nut for domed LED, etc.

Depending of LED, its adviced to tin its leads before attaching. Some are difficult to tin, some not. But leads generally may be solder directly.



LEDs have polarity, so it matters if putting the + electrode up or down.

High power LEDs are conected in series, what mean that you conect the + of one to the - of next. If you put all LEDs on same position, wires used to connect them go doing zigzag (Z). While if you alternate the position of electrodes (one, +up, next, - up, next + up and so on) you connect them with straigh wires.

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delta9nxs

good to see you still here! i haven't posted here for a while as i have had serious health problems. i've always enjoyed your analytical and common sense approach to solving problems or examining some aspect of our hobby. i was just thinking about leds the other day and wondering if they had become practical. was surfing around looking for info and thought, "i wonder if knna has anything on this subject?" i come over here and i find you conducting a tutorial! perfect timing!

i would like to replace 4 1kw hortilux with leds sufficient to acheive the same growth i get now. right now i have to run cool tubes with 4 500cfm exhaust fans and ac to keep things cool. the electrical savings would soon offset my cost for constructing leds. plus the stealth factor would go up radically.

i'm on board for this show and will try to build my own array using your help. thank you, delta9nxs

tripps

Great info, as always, Kenny. ( I thanked you too many times to rep you)

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knna

Hey, delta, Im very glad to see you again. Its been a long time!

About your project, although LEDs has become practical lately, and they are able to grow excelent weed and with well built systems using good LEDs, surpass HID yields (watt per watt), they still arnt cost effective on large setups.

They do on small ones due small HID lamps are more expensive than large ones (on a watt basis, and still more on a uE basis) , and on small cabs heat is usually a problem.

If I reccomend to wait before replacing large HIDs is because LEDs perfomance are greatly exaggerated on most sites. If you want to keep harvests constant, you need to install 50-60% of the watts already installed with HIDs. So to replace a 4000W HPS setup, you will need to install about 2000-2400W of LEDs. At about 3$/W minimun, its going to be over 6000$. Recover it from electric savings is going to be difficult, still taking into account the reduced cooling requeriment.

LED perfomance/price is improving at a rate about 30% each year. Next year its going to be easier to replace HIDs, and probably we will know way better what spectrums to install and how many watts of LEDs are required. For me, although its now proved that LEDs works for growing, they are still on the experimental stage.


knna

We are still learning how to use LEDs the best way. Nobody has found the optimal spectrum for cannabis yet. I would say to wait a year before thinking on replacing large HIDs is wise.

If any, I would think on reducing top HID lighting density, for example putting 2 or 3 1000watters on top instead of 4, raising them or opening reflector's wings if possible and supplement it with LED modules on bottom areas. This will enhance light distribution and keep yield constant using less watts, while keep initial investment controlled.

Im currently testing a 60W LED module, designed to work in sidelighting or intracanopy (its just 3mm thick, with 6 boards of 22*4cm each, 10W). Those 60watts produces 90-100uE of deep red, expected to yield about 100-120g of dry bud. If it works fine on tests, Ill produce it on large amounts. Price will be about 180€ (about 235$) on hydro shops, but I would like to offer them on the forums for about 140-150€ (180-190$). If they able to increase yield on those 120g (4oz), I think they are going to be an excelent way of improve current HID setups. But tests have just started, Ill know on 2 months if they work as expected.

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knna

Now we have LED attached to the heatsink. All we require to finish the lamp is to conect them.

As explained on last post of the tutorial, we wire them in series: + to - to +...

Each model of LED has its own way of marking what lead or contact is + and -, so I wont enter on it. If you had problems identifying them, upload a pic and ask .

On the last pic with the LED attached to the board, the up side is - and down lead, + (the mark is the ESD diode on the side of - contact, for the Golden Dragon).

Once LEDs on the board, take wire between the 2 contact to being soldered and cut. Peel off the cover of the sides, about 0.5cm or a little more. Tin both ends of wire (heat with the solder, about 1second and add the tin). Its preferably to tin too the LED's lead, by same procedure: put the solder tip on it, for 1-2 seconds, and add the tin. Most leads takes it very well, with some models you need to heat them for more time. For models a bit more difficult, a bit of solder flux helps.

Once the wire and the lead are tinned, put the tip of the solder on the lead. the wire on it, holding it with the tweezers, until the tin gets liquid. Retire the solder, and continue holding the wire for a while, until the tin gets solid again (usaully, 1 second or less). Its done.

Repeat the process for each contact, until finish wiring the serie. Any serie is going to start with a free - contact and finish with a + contact. They are what are connected to the driver output, usually marked + and -.

Positive output of the driver to + free contact of the serie, negative to negative. A good practice is to finish the string with a piece of electrical conection, with the wire to the free contact on each side of one hole of the electrical conection piece. It makes very easy to wire the driver, as a ballast, change how you wire series (sometimes its possible to connect 2 series in paralell to one driver, and run them at half power, etc).

I like to cover all wires and solder points with kapton tape, in order to protect them against humidity, etc. But do it after checking all is OK.

You just need to connect the driver to the mains to have your LED lamp working.

A good practice is to check all LEDs and their conections before lighting on them. You need an electrical tester to do it. Typical cheap ones are more than enough for this purpose. On a next post I will detail how to use a multimeter to check the instalation, to measure forward voltage of LEDs and current of the string.

(Ill try to add some pics to this post. Although its should be very easy to understand to anybody used to solder, maybe others dont see it so obvious)

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igrowwitmatches

Great stuff... still learning love the pictures

Edit: this backwards thread stuff sucks