The DIY LED Help Thread - Diodes, COBs, Drivers, Sinks, and Tools

Hey GC!

Some of you may have seen me around the city for awhile now! I'm not the most experienced blade but I have become fascinated with the LED lighting scene and being both a hands on learner and a PC technician, DIY LEDs are something I gravitated towards. I'm working on my first DIY light currently and have seen a good bit of interest around the city in building and repairing or upgrading panels. In my quest for help I have always been directed to another forum where all my questions have been answered. I hope to build the same thing here! Our own GC DIY LED thread.

I will continue to post various tips, tricks, tools, and arithmetic that apply to DIY LEDs.

I will also be doing my best to answer any questions that may be posed!

I also hope to have people contribute their knowledge and experience they have had with DIY LEDs.

Finally for now I think it would be really cool to come up with an index of sorts for suppliers of diodes, chips, sinks, fans, tools, connectors, drivers, etc

Anyways I hope we can make this an active thread with lots of positive interaction!

Peace & Love
PyspherE

 

Okay so I'll start at the beginning. For myself when trying to complete a build list I always start with my target output wattage. The next thing remember is you generally want to run your LEDs at half their rated maximum current! So if your looking for a panel to output 300w, you need to look for a set of diodes that can handle a maximum of about 600w. This is simply to extend the lifespan of the diodes. I will expand on this in a later post. For now just know running g them soft gives you good light output and good diode longevity. Now that you have your desired output the fun begins! Finding the COBs and/or diodes to give you the desired Wattage and Spectrum.

 

So for the sake of continuing an example I will start compiling a theoretical build for a 300W output LED. Couple things to consider first. My first to myself is always spectrum. If you want any off white spectrums like deep reds, ambers, blues, etc you are pretty limited to strings of single diodes. If you're looking for a straight white light approach you can have the option of stringing single diodes or using few COBs. COBs or Chip On Boards use a Micro array of many many tiny didoes prewired on a wafer. These offer higher wattage chips and are the more recent development in the LED world. I personally can't speak to the efficiency of COBs over Diodes or vice versa. Now there is one more alternative and that is a mixture on COBs and diodes. They cannot go in the same string but can be mounted to the same heat sink with different drivers!

 

Continuing with the previous example, for the sake of including both a diode array and COB array this theoretical build will use ~100W of colour specific diodes and ~200w of white COBs. I will start with the Diode string that will run ~100w. I'll start with possibly the most important equations you'll use in calculations for your build. Watts = Volts x Amps. Diodes and COBs for the most part have their current or Amps measure I'm mA or milliamps. 1A = 1000mA. For simplicity sake I'm going to choose the Cree XP-E series of Diodes that come in various wavelengths and run at a maximum of 3W. This means to generate the 100W of output at 50% efficiency we need 66 diodes to hit 99w. So let's break this 66 diodes into a mixture of 20 royal blue, 20 photo red, and 26 far red. Here is the manufacturers site for these diodes. http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Discrete-Directional/XLamp-XPE . As you can see they are rated for a maximum current of 1A or 1000mA and run at an typical forward voltage of 3.1V. To power these LEDs we will need a drivers capable of delivering 3.1V x 66 diodes = 204.6V at about 500mA. I will get into the drivers later!

 

Sick builds Witch!! Those guys over there definitely know what they're doing! I've found good help there in the past! I'll be back with more posts today to continue this theoretical build we've started!

 

Okay GC, so he have our Diodes picked out for our first string! As I mentioned at the end of my last post we will be running 66 diodes which each use a forward voltage of 3.1Vdc. This means our string needs a total of 204.6Vdc. Let's quickly forget Volts for a moment and look at the Amperage as well for a moment. This string uses diodes with a maximum current of 1A. Now in a series circut every component receives the full current of the circut. That is to say if the driver was 750mA, each diode will operate at 750mA. In order to run your diodes soft, this is the way to do it. By changing the current we can change the brightness of our chips an conversely the operating temperature. So with this string of diodes rated for 1A or 1000mA we will look for a 500mA driver. Okay back to voltage! So this is where you can make some decisions. Because we need 204.6v from our driver we can look for 1 driver to power the whole string that can operate at 204.6V @ 500mA or we could look for 2 drivers that can handle 102.3V @ 500mA or you could do 2 drivers that run 62v @ 500mA plus one running 80.6v @500mA. As you can see you have some options. To keep this build list as simple as possible we will go with a single driver. For this string I would choose a Meanwell HLG-120H-C700. This driver runs at a constant current or Amperage of 350-700mA which covers are target of 500mA. It also has a variable voltage output from 107Vdc to 215Vdc which meets or needs of 204.6Vdc. This should power our string of XP-E diodes nicely! You can find the data sheet here, http://www.meanwell.com/webapp/product/search.aspx?prod=hlg-120h-

 

Now that we have our coloured string picked and powered we want to move on to the ~200W white COB portion. For this portion I have again chose to go with another Cree option. This time to hit our 400W maximum draw number we can go with 3 of the Cree CXB3590 COBs. You can find the manufacturers product page here, http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Arrays-NonDirectional/XLamp-CXB3590 These have a maximum draw of 137W each with a maximum current of 3.6A or 3600mA and a forward voltage of 36Vdc. So to power these super high powered COBs we need drivers capable of 36v x 3 COBs = 108Vdc. The drivers should also be able to operate at about 1.8A or 1800mA. We'll look at these drivers in my next addition to our theoretical build!

 

Okay so let's find some power for these COBs. Because they are so high powered I would not suggest going beyond 3 or 4 of these COBs in series at 50% draw. Because we are only using 3 we can wire them all together to a single driver, or power each with its own driver. For simplicity sake I will run them all with a single driver! To recap our COB string needs 108Vdc at a constant current of about 1.8A or 1800mA. For this driver I going to list 2 options. First I will list what I would call the smallest driver for the job. It's the Meanwell HLG-185H-C1400. This operates at 71-143Vdc with a constant current of 700-1400mA. This driver would give you pretty good results but we would be running below our target of 50%. This isn't harmful to run this soft by any means and so this driver would be a good option. I personally would recommend the Meanwell HLG-240H-C2100. This driver will be more expensive but will allow you to drive the LEDs a bit harder to hit the 50% mark. This driver can handle 59-119Vdc with a constant current between 1050-2100mA. This gives us the flexibility to run the COBs from 30-60% of their maximum as opposed to driving them at only 20-40% with the first driver! Here you can find the data sheet for the driver http://www.meanwell.com/webapp/product/search.aspx?prod=hlg-240h-c

 

Okay! So we have our COBs and diodes picked! We have the power sources picked! Now what? Now it's time to cool these expensive parts!!! When it comes to cooling, its hard to overkill. I always suggest starting with a nice thick, high quality, extruded aluminium heat sink for a light the size of our theoretical build! The bigger the sink, and the higher the quality, the cooler your able keep your electronics and therefore they last that much longer and put off less heat. Yes less heat. I know you've always been told that 1W of heat is always 1W, but with LEDs as you are able to run them cooler at the same Wattage input they are able to output more light. That is to say, the cooler they can be kept by a larger sink the more efficient they are! For our build I would look for a nice chuck of extruded aluminium. Personally I would look at a 8.46" wide profile like this http://www.heatsinkusa.com/8-460-wide-extruded-aluminum-heatsink/ I would look at using probably a 30" long piece. Because I plan on using fans to cool the heatsink directly 30" of this heavy sink should do great. Next post I'll get into actively cooling the sink and other cooling options!

 

now we have have a hunk of aluminium we want to keep it as cool as possible. For this we use fans. If you wanted a fanless option you could look at going up to +36" long sink and then use the adjustable drivers to throttle back the power to keep your temps at a desirable point! With our theoretical build I'm going to use 3 x 120mm Delta Server fans. You could use any PC fans really but my personal preferences from years in the enterprise server market are these http://www.delta.com.tw/product/cp/dcfans/download/pdf/AFB/AFB120x120x38mm.pdf because of their very high flow rate. For some, noise is a concern and in that case standard PC grade fans can be used as a cheaper, slightly less effective alternative! These fans run at 12Vdc and pull an average of 450mA. My next post will get into powering these fans!