DIY LEDs - The write-up

[pheinzig]

THX lav.

I indeed have the ELN-60-48D series from meanwell.
And in concordance with the mainstream, I will be running 12leds per driver.

I haven't gotten down to the wiring, but thats a few days away at least. So If I get stuck Ill ask.

Currently Im about to start tapping the screws.I look foreward to showing everyone the fruits of my labor soon enough.

 

[jiriki]

I just finished a protoype LED strip which I wanted to use as a supplement to my MH setup. I am using 13 LED's on a 1.5" wide by 23" by 1.5" tall heatsink.

I haven't gotten the dimmable part to work yet. However, with a 10v wall regulated wall wart, I am able to run the Meanwell at 100%. After about 15 minutes, the heatsink gets too hot to touch any longer than a few seconds. Obviously, I need to use fans.

How hot can the heatsink run at before they start to fail?

 

[FW fugitive]

I am looking at either using alternative drivers like those form Thomas Research Products.

Interesting products. Do you have a price or distributor? Maybe the google just isn't working for me...

Does it make more sense to increase the voltage, so I can have longer strings (36-40 LEDS on one string)per driver? Or would it be better to increase the current, so I can have more parallel strings (4 strings of 13)?

Parallel strings bring their own headaches, as discussed on this thread. You have to find a way to even out the current through the different strings, and protect the rest of the strings should one string fail. I'm not sure I've seen a good solution to this problem.

On the other hand, the voltage required for 36-40 LED's in series would be hazardous (approx. 120VDC). It appears that anything above 42-60 volts (depending on the source) is considered high voltage & possibly lethal, AC or DC.

So it kind of depends on your DIY safety/comfort level. I personally get nervous working with that kind of voltage, but I'm mistake- and accident-prone. So my tentative plans are to build several smaller units, making sure of course that I don't run into the multiple PS harmonic issue addressed earlier.

 

[TheFishMan65]

I think it was kcress that said if you can comfortably put your hand on it you are ok. Of course I had a Scout Master that put his hand in boiling water and said it wasn't hot enough to clean dishes . Having said that I think the numbers I have heard is about 100 degrees fahrenhieht.

 

[Jay1982]

I have the meter to 10A. Trying to read the amperage. I want it set to 750mA

 

[TheFishMan65]

OK. Not sure what you are asking.

 

[spamreefnew]

thanks to cjo! do you guys think its better to buy parts or to just order a kit from rapidled.com? i am very tempted to just buy the 36pc kit from rapidled

 

[jiriki]

Just measured the temp on my heatsink with no fan cooling.. 151 degrees F

Looking at some 40mm fans now...

 

[Jay1982]

OK. Not sure what you are asking.

Me? I'm confused

 

[pheinzig]

I just started tapping my heat sinks.
I was having trouble early on. I asked my dad for advice, and he produced a can of "Tap Oil" Keeps the bit cool, and clean. I put a drip on each hole, and on the bit each time.

After that tapping was cake!
So anyone else out there reading, be sure to use some kind of oil when you tap your screws. I don't foresee me breaking tons of tap screws as is the trend I see often on these projects.
*knock on wood*

 

[pheinzig]

A preview:

 

[jiriki]

If I am reading the Cree datasheets correctly.. 150 degrees F isn't terrible. They measured output from 77 degrees to 150 degrees F. It runs the most efficient at 77 degrees. Maybe I am reading the datasheets wrong? I am using XR-E RB and XP-G whites. I'm still going to get fans but it seems like 150 degrees isn't necessarily in danger blowing out the LED... maybe someone can confirm.

 

[pheinzig]

get fans. you only do good by adding cooling.
Longer life, more efficiency.

 

[jiriki]

I'm going to do so.. just saying.. 150 F is within specs... though.. at about a 20ish% loss in efficiency for XP-G's... XR-E's RB.. it seems be around 5%. Not much difference for royal blues for some reason..

 

[westmoorenerd]

pheinzig- what fans are those?

 

[pheinzig]

pheinzig- what fans are those?

Coolermaster 200mm PC fans. Absolute silence! They claim 19dba, I dont believe it, its quieter than that
And pretty descent airflow to boot.
http://www.coolermaster-usa.com/product.php?product_id=2946
Ill have 1 12v wart, with 3 "Y" cables to split it to 4 fans:
http://www.rapidled.com/servlet/the-49/12V-AC-Adapter/Detail
http://www.rapidled.com/servlet/the-69/DC-Jack-Adapter/Detail
http://www.rapidled.com/servlet/the-68/Fan-Y-adapter/Detail
The wart is a 6w, and each fan needs .28 to run at max speed.
So I can handle 4 easy.

 

[laverda]

Interesting products. Do you have a price or distributor? Maybe the google just isn't working for me...

Their web site list distributors for some states, for others it says to call them. I could not find pricing either and of course that is a factor.

Parallel strings bring their own headaches, as discussed on this thread. You have to find a way to even out the current through the different strings, and protect the rest of the strings should one string fail. I'm not sure I've seen a good solution to this problem.

On the other hand, the voltage required for 36-40 LED's in series would be hazardous (approx. 120VDC). It appears that anything above 42-60 volts (depending on the source) is considered high voltage & possibly lethal, AC or DC.

So it kind of depends on your DIY safety/comfort level. I personally get nervous working with that kind of voltage, but I'm mistake- and accident-prone. So my tentative plans are to build several smaller units, making sure of course that I don't run into the multiple PS harmonic issue addressed earlier.

I know about the parallel strings, but I don't think that should be that big an issue. I would want to run at least 4 in Parallel, if I go that route, so I don't think the Mean wells would work.
I am not worried about the voltage per say as I am comfortable working with electricity, but it is something to keep in mind around saltwater. Lower voltage and amperage would be better. Amperage is what will kill you more then volts.

 

[westmoorenerd]

pheinzig- That 200mm fan actually needs 3.36w@12v to run at full speed, so with 4 hooked up to 1 6w/12v wall wart you're going to be driving them at roughly 45% max speed.

 

[TheFishMan65]

jiriki,

The heat sink is running 150 degrees, but CREE is specifying the junction temperature which is something we can not read. As I understand it the junction temperature is inside the LED. It then heat sinked (sunk?) to a piece of metal that leads outside the of the LED. That is then mounted to the star board and heat sinked (sank?) to the backside aluminum core. Which if you did a good job is heat sinked to the heat sink. How far away from the center of the LED are you and how thiick is the aluminum. If you had a 90 efficiency at each junction (don't know if this is reasonable or not) then the junction is close to 205. I am sure someone will come along and correct something I have said.

 

[hllywd]

jiriki, I don't know if you've seen my build or not, I posted a couple pics in the CORA forum, but at a lower power setting (~300mA) my heatsinks are luke warm to the touch running all day. After 45 minutes at ~700mA they'd be a nice hand warmer on a cold winter day. I don't have a better way handy to measure the temp, but nice and warm to the touch makes me want to get my fans up and running before I drive them like that for long. Too hot to keep my hand on would require an immediate solution from my limited knowledge on the subject!
I don't know much about the details of heat transfer from the LED junction, to the star, to the heatsink, but 151°F on the heatsink sounds pretty hot. Is that measured on the fins or the base plate? If it's the fins, I'm sure you can count on the base plate being even higher, and the LED temp higher still like TheFishMan65 said.

Tim