COB Compatible LED Drivers

[Firebrand]

Gonna throw this into the thread for those who are interested in heat dissipation.

There is a rough formula of for the temperature rise.

As a very rough "rule of thumb" you need 1 sq inch of surface area exposed to the open air for every watt of LED on the heat spreader (Heatsink) w/o fan forced cooling.

With a cooling fan in operation you will be well within the parameters of the required cooling temps @ 1 sq inch per watt.

Below is a small primer on matching COB's to drivers.

http://www.digikey.com/product-search/e ... 00N00V427F

Looking at page 17 of the LED data sheet you could run maximum current (2.4 amps) if you had to. But to insure long life of the chip 75% of that or 1.75 amps would be a prudent number.

Then looking at page 9 of the data sheet you can see Vf (forward voltage) of the LED at 1.75 amps is around 38 or 39 volts. After that it's just a search for a driver to match 1.75 amps and at least 39 volts.

 

[RedDirtWarrior]

the plate is made of aluminum so it will have to be completely striped down to bare metal, from there it will have to be sanded and polished to insure that heat transfer is at a premium.

Have you considered using thermal paste on the bottom of the heatsinks where they contact the metal? (PC's processors have this on heatsink connection)

OR does the metal not conduct enough heat for this to be necessary? I would think the COBS have much more heat concentrated into a small area and thus, need a heatsink for this, the spread out heatsinks wont do much good with the COB.

 

[sammyz2646]

The overall MASS of the heat sink dictates the overall amount of heat it can handle---- via absorption------then dissipation.. This is why a bigger heat sink is necessary in some cases for more powerful COB's

The COB is small and very hot at the actual contact point---and excessive heat is then transferred into the extra space inside the aluminum ---to be pushed off and away by additional heat that sort of spills off after the heat (tank) is full---so to speak . The bigger the sink---the bigger the "tank" . It holds more heat for longer

 

[Firebrand]

Have you considered using thermal paste on the bottom of the heatsinks where they contact the metal?

I covered this briefly at the end of post #16.

....be sure to use thermal grease between all mounting surfaces.

It should be a given that thermal paste or thermal pads are to be used between mounting surfaces.

Considered by many to be the best.
http://www.arcticsilver.com/as5.htm

http://www.amazon.com/Arctic-Silver...448248&sr=8-1&keywords=artic+thermal+compound

StarTech Heatsink Thermal Pads.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835230030

 

[luvdemshrooms]

I'd stay away from pads and would instead use the thinnest possible layer of grease.

Less IS more.

 

[clp]

Hey Phat Mike - Where did you find the AB bins for the 3070s? I can't find them anywhere and I'm a bit of a google whiz. Thanks

 

[phatmike]

"Hey Phat Mike - Where did you find the AB bins for the 3070s? I can't find them anywhere and I'm a bit of a google whiz. Thanks "

I found them on www.cxa3070.com after a long research. They are not cheap (60 each) but they are available now.
PS
They only have 3000K

 

[phatmike]

Sorry another question: I just received the CEN 100 42 driver that I will use to drive the 3070. On the back there are two little screws, one to adjust the V and another for the A.
The problem is: How I know (no numbers, no graphic references) if I'm at 2,3 A or 1.4 A (the one I want). Do I have to set the V screw too? I'm really a newbie (in electronics) but I really want to build my first lamp. Thank you.

 

[Firebrand]

Sorry another question: I just received the CEN 100 42 driver that I will use to drive the 3070. On the back there are two little screws, one to adjust the V and another for the A.
The problem is: How I know (no numbers, no graphic references) if I'm at 2,3 A or 1.4 A (the one I want). Do I have to set the V screw too? I'm really a newbie (in electronics) but I really want to build my first lamp. Thank you.

You will need a volt/ohm/amps multimeter, preferably a digital type. Another option might be to ask 3rdDream about adjustments as I believe he uses the same driver.

This from Don Klipstein in post #5 of this thread.

COB LED's like most other LED's have a nominal current rating and a nominal voltage rating. They also have a maximum current rating. I suggest not exceeding 75% of the maximum current rating until you have good experience with LED's.
[FONT=Arial, Helvetica, sans-serif]
LED drivers usually have a current rating and a voltage rating. The current rating should be what you want, and the voltage rating should be significantly higher than that of your LED (or LED arrangement).[/FONT]

[FONT=Arial, Helvetica, sans-serif]What's being said in the quote is that it is alright to have excessive voltage but be careful not to exceed 75% of your COB's current rating.

If you over amp a COB you will have an SED, (Smoke Emitting Diode).

[/FONT]

 

[clp]

"Hey Phat Mike - Where did you find the AB bins for the 3070s? I can't find them anywhere and I'm a bit of a google whiz. Thanks "

I found them on www.cxa3070.com after a long research. They are not cheap (60 each) but they are available now.
PS
They only have 3000K

Thanks PM!! Have you actually ordered and received the units from here? Site looks very new and I don't trust every site on the web.

 

[phatmike]

Thanks PM!! Have you actually ordered and received the units from here? Site looks very new and I don't trust every site on the web.

I have them in may hands. Holders are on the way. Fake? I know there is some risk in buying like this. Anyway, I will try everything in few days. Wait for my test and then decide.
PS
The seller was selling the same bin on ebay and somebody here in the forum bought it. But I don't remember who.

 

[Firebrand]

Here's an interesting article on MacAdam ellipse theory and BIN correlation. It is technical in its writing and may not appeal to everyone, none the less it is posted here as reference.

When white light isn’t white.
http://www.mikewoodconsulting.com/articles/Protocol Spring 2008 - White is White.pdf

 

[Firebrand]

I'll bump this up for those who are new to Do It Yourself LED construction including basic knowledge of how it works.

 

[Dion]

getting involved, i see some peeps i know are already here. hi !

 

[budlover123]

Here are a couple tools for those who are burgeoning LED do it yourselfers.

LED Series Resistor Calculator
http://www.hobby-hour.com/electronics/ledcalc.php

LED series/parallel array wizard
http://led.linear1.org/led.wiz

Hello. I'm not 100% sure. Please, someone correct me if I'm wrong, but I'm pretty sure these calculators deal with the older, constant voltage type LEDs and not the newer 1-100watt, constant current LEDs. I'm also pretty sure you typically don't need/want to use resistors on modern constant current LED circuits.

As far as driver compatibility goes, as long as the COB LED's forward voltage isn't too much for the driver, like as in a 35V LED on about a 40V driver, you should be fine. Putting 2 35V COB LED's in a series would be too much for that driver, but putting 2 of them same LED's in a parallel circuit would be fine, just half the current output.

IMO constant current LED circuits are MUCH simpler and easier to design than the older constant voltage types, probably why they don't have calculators for them.

 

[Dion]

Hello. I'm not 100% sure. Please, someone correct me if I'm wrong, but I'm pretty sure these calculators deal with the older, constant voltage type LEDs and not the newer 1-100watt, constant current LEDs. I'm also pretty sure you typically don't need/want to use resistors on modern constant current LED circuits.

As far as driver compatibility goes, as long as the COB LED's forward voltage isn't too much for the driver, like as in a 35V LED on about a 40V driver, you should be fine. Putting 2 35V COB LED's in a series would be too much for that driver, but putting 2 of them same LED's in a parallel circuit would be fine, just half the current output.

IMO constant current LED circuits are MUCH simpler and easier to design than the older constant voltage types, probably why they don't have calculators for them.

yup, these ac-dc drivers dont need resistors, and you are correct now we adjust the amps not the voltage to drive leds, most drivers auto adjust the voltage within thier range/


i wonder whatver happened to phatmikes build?

 

[luxcultivars]

I'm going to throw this into this thread as an example of learning on the fly.
................
Enter COB technology, simplification of string type circuitry, all the beads on one single module and the manufacture does the work. All the DIY guy has to do is match up the correct driver and make sure he has enough heatsink/fan action and he's up and running.

Now, back to those EBay China fixtures. As can be seen from the photos above, there are many salvageable parts, those parts being (4) drivers, (3) fans, a power supply for the fans, a large heatsink and a decent pre made cabinet that houses those parts.
...........
My mission was to match a COB or even Multiple COB's to those drivers so that they might be usable.
...........
If this works out I hope to get about 210-220 total watts of COB LED light out of the fixture, figuring in energy needed for cooling the fixture it should still be above 90% efficiency.

As I move forward I will update. If any of you find my logic incorrect please correct me, I am still learning, thank you.

Well? What did you come up with? How'd it do? Did I miss your update?

 

[Firebrand]

Well? What did you come up with? How'd it do? Did I miss your update?

I'm tight for money and can't afford the parts, heating season this year has absolutely drained me and my savings account.

I hope to follow through with my plans a few months from now, please check back in May or June, and thank you all for looking in.

 

[The Dopest]

Stupid question here but I didn't want to start a new thread for it, besides, someone may learn from my ignorance.

Say you have a CXA3070 and want to run it at 1400ma and about 50w. The driver says it's 1.4A and 60w, how many amps does it actually pull, roughly?? About .5A from the wall? Running four would be about 2a total?

Thanks in advance!!

 

[budlover123]

The 60-watt on the driver is an actual watt rating, meaning that driver will crap out if it tries to draw above 60-watts and should probably not be drawing more than 50-watts for safe operation, don't worry about watts when it comes to the LEDs, that's just marketing IMO, if the driver is putting out the 1.4A to the LED and not drawing much more than 50 watts from the wall, that's all good. A driver is rated for 100-watts 1.4A, puts out 1.4A to the LED and draws 90 watts from the wall, all that means is it's less efficient than the 60-watt driver

amps from the wall would be the amp draw of an AC appliance running at 60-watts, which I'm not too sure about, here's a website talking about it
http://www.metrosolarmatics.com/applliance-wattsamps-calculator.html

but I don't know about that, there's no way the Amp draw for AC appliances what they list, most circuits are 15Amps, according to that 2 old school 100 watt lightbulbs would be maxing out your circuits and that's not the case