First LED build

[shark565]

Hello everyone, I am planning an upgrade of my 6 gallon pico and I need some help with the new LED lights. The new tank is going to be 50sm cube with another 10 sm on the bak for internal sump. I will be usung 5 x9w royal blue LEDs. I bought a power supply with 12v DC output current, but when i wired one LED , just for a test it started glowing then stopped and in my opinion died. Should i be using resistors or smth?
P.S. I am a complete newbie with all the LEDs and everything. Sorry if my question is stupid.

[Webmanny]

I would need to know a bit more about your LEDs to better assist. Do you have a link to where you got them out their specs?

Normally 9w LEDs are 27v and this could be why yours are not lighting up or it could be that they are lower voltage and you just fried them.

Either way could be right, but I need more information to be able to assist.

[oreo57]

I would need to know a bit more about your LEDs to better assist. Do you have a link to where you got them out their specs?

Normally 9w LEDs are 27v and this could be why yours are not lighting up or it could be that they are lower voltage and you just fried them.

Either way could be right, but I need more information to be able to assist.

Plenty of 12V 9W LEDs..
Even 3 3W in series is in the 10-12v range..
though it solves nothing.. ;)
http://www.dx.com/p/9-x-1w-9w-led-emitter-on-38mm-base-11v-12v-500-lumens-white-6500k-700ma-5862#.VZjGD7GrPO8

3x3 arrays...

[shark565]

The Leds are like these : http://www.aliexpress.com/item/EPILED-45MIL-10W-Royal-Blue-450nm-High-Power-LED-Multichip-Intergrated-Light-Source-for-Aquarium/1733139222.html
So, I think I should drop my voltage to 10v ,but I don't know how.

[oreo57]

The Leds are like these : http://www.aliexpress.com/item/EPILED-45MIL-10W-Royal-Blue-450nm-High-Power-LED-Multichip-Intergrated-Light-Source-for-Aquarium/1733139222.html
So, I think I should drop my voltage to 10v ,but I don't know how.

The "best" way is to add a constant current driver between the ps and the led..
One for each chip:
not knowing the chips specs...this comes to mind:
http://www.rapidled.com/mean-well-ldd-700hw-dimmable-driver/

That said ther are numerous ways to drop the ps voltage.. from series diodes and using their natural voltage drop to terminating resistors on each LED using calculators such as this:
http://led.linear1.org/led.wiz

as a "guess" using a 4.7Ohm 5W resistor on each chip run in parallel "MAY" work. That should get the diode voltage to 10V
But this can go all over the board w/ out more info.. A 2.2Ohm 1W may work as well... Diode voltage will be 11
Def. need more info and study.. ;)

oh and doing this your ps needs to be capable of 4-6A output..

note all this is pure "guesstimate" but should be in the ballpark...
BTW: those chips have 3 diodes in series and 3 parallel sets of them...
Diode voltages add in series (so whatever the V(f) of each times 3
Amps add in parallel..
so to backtrack a bit each ind. LED within the chip have a rough spec of:
10/3 = 3.33V @ 1000mA /3 = 333mA...

Sooo w/ a 700mA driver they will be comfortably below spec at .700/3 = 233mA

[shark565]

My ps is capable of 6A output. If i run 5 LEDs in series. They won't burn, if i understand right. The LEDs are not that expensive, but I waited 3 mounths to come from China.
Should i try running 5 of them in series or the danger of frying them is too big?

[zachts]

My ps is capable of 6A output. If i run 5 LEDs in series. They won't burn, if i understand right. The LEDs are not that expensive, but I waited 3 mounths to come from China.
Should i try running 5 of them in series or the danger of frying them is too big?

5 in series won't light off a 12v supply, only way to drive 5 of them is in parallel In which case without something regulating the voltage (and subsequently the current) they will burn right out.

One LDD driver between the psu and each LED is really the best way to go. However if the PSU is adjustable....

Is the powersupply voltage adjustable?

If it is you can squeak by with just using the voltage adjustment to dial in the current to the LEDs. The down side is you will want to keep them well under spec at or below 500mA to allow for current increasing as the LEDs heat up (at a fixed voltage the hotter they get the more current will flow which is bad). You'd also wan't to get a 5watt 1ohm resistor for each LED chip to allow you to easily check the current (mV measured across the resistor in this case equal the mA running to each LED).

Turn PSU voltage way down, connect the LEDs, slowly increase voltage while monitoring the current to each LED until one of them hits 500mA roughly, then let them run for a few hours monitoring current and decrease voltage if any of the LEDs start to increase current by more than 100mA from where the started. Be sure the LEDs are mounted to their heatsinks for this otherwise they'll burn up pretty fast.

The down side to doing this is that the LEDs will not all be driven equally, one will draw more power than the rest and this is the limiting LED that will set the voltage seen by the rest and therefor thier brightness.

[oreo57]

As Zachts says..

1 in series = 10 volt 2 = 20v 3=30V ps needed... ect..

Just get some cheap resistors.. Run all chips in parallel

https://tubedepot.com/products/5-watt-power-resistor?gclid=CKmuq6jxxMYCFQ-PaQodHjgJgQ

Pick one 45 cents each x5

3-5Ohms..

[Bootlegger]

Two problems you're going to face. Most cheap power supplies are not voltage regulated. And second, assuming you have enough drive current, it needs to be regulated also. Thus, as Oreao57 said, you at the very least need some resistors.

The LEDs you're using usually have the following power specs:
Forward Voltage: 9-11v
Forward Current 900ma-1050ma

Depending on the output of the power supply you're using, without a resistor or proper LED driver, you could easily be driving too much voltage or current. Odds are you burned out your LED by overloading it.

Buy yourself a proper LED driver. Most people wire LEDS in series, which means for you to run 5x 10watt LEDs, you'll need at one driver capable of 52V output or two 48V drivers. Don't buy a driver capable of less than 50 watts.

[oreo57]

One more thing.. Even "if" you drive those chips at a fairly low mA level (unless really low) if you don't have them heat sinked you will still probably burn them out..

sooo even if you are just "testing" them.. attach them to "something" aluminum or copper.. ;)

[Bootlegger]

+1 to Oreao57 says. I burned out many a cheapo Chinese LED "testing" them without a heatsink.

[Icefire]

Sorry to say this but if you don't know how the ohm law work, if you don't know basic electronics, you shouldn't attempt this without someone who know something.

First, led need to have the current regulated, with a serie resistor or a driver. Next you need to manage the heat.

Next thing we will know someone will start an electric fire..

[shark565]

I have a heatsink and a fan for cooling it , also I bought a thermal paste. Tomorrow, I am going to buy some 5w 4 om resistors, wire the LEDs and the resistors in parallel and attach the LEDs to the heatsink. Can i put thermal paste under each LED and then solder it to the heatsink ?

When I tested the LED and it burned , I haven't attached it to the heatsink.Could that be the problem , not the ps and the voltage? Because, it was glowing for like 10 seconds before burning.

P.S. Icefire, you are completely right ,but I want to learn how to do it and I have nobody to ask for these things.

[oreo57]

I have a heatsink and a fan for cooling it , also I bought a thermal paste. Tomorrow, I am going to buy some 5w 4 om resistors, wire the LEDs and the resistors in parallel and attach the LEDs to the heatsink. Can i put thermal paste under each LED and then solder it to the heatsink ?

Normally you don't solder it to the heat sink. Either use screws or something like thermal epoxy or "heatsink plaster"..



When I tested the LED and it burned , I haven't attached it to the heatsink.Could that be the problem , not the ps and the voltage? Because, it was glowing for like 10 seconds before burning.



It was probably both... You always need to control the current and heat w/ an LED

http://electronics.stackexchange.com/questions/55823/how-can-i-efficiently-drive-an-led

[zachts]

One more thing.. Even "if" you drive those chips at a fairly low mA level (unless really low) if you don't have them heat sinked you will still probably burn them out..

sooo even if you are just "testing" them.. attach them to "something" aluminum or copper.. ;)

+ 10, can't stress this enough. 100 mA would mot likely be enough to overheat those multi chips without a heatsink if powered for more than a couple seconds. and at full power a second or two would be all it took to kill them...... If I knew how to "bold" text in these posts I've have highlighted that bit in my previous advise.....

[Icefire]

I have a heatsink and a fan for cooling it , also I bought a thermal paste. Tomorrow, I am going to buy some 5w 4 om resistors, wire the LEDs and the resistors in parallel and attach the LEDs to the heatsink. Can i put thermal paste under each LED and then solder it to the heatsink ?

When I tested the LED and it burned , I haven't attached it to the heatsink.Could that be the problem , not the ps and the voltage? Because, it was glowing for like 10 seconds before burning.

P.S. Icefire, you are completely right ,but I want to learn how to do it and I have nobody to ask for these things.

Resistor need to be in series with the led

I would use one 5W 2 ohm in serie with each led and wire each duo in paralel.

Remember the led as a polarity

[shark565]

I am so mad at the moment. I used 2,2 om 5w on one LED just to try if that fixes my problem and it did. However, my order came wrong . I tested every LED and all of them are white. Can i use only whites untill i order some royal blues? Can the corals use white for their photosyntesis? Is there any chance that i am doing something wrong and that is why they glow white?

[letoan]

I am so mad at the moment. I used 2,2 om 5w on one LED just to try if that fixes my problem and it did. However, my order came wrong . I tested every LED and all of them are white. Can i use only whites untill i order some royal blues? Can the corals use white for their photosyntesis? Is there any chance that i am doing something wrong and that is why they glow white?


Some light is better than no light. White LED is white LED, they either lit or don't.

[shark565]

So, i am going to wire the whites and order some royal blues today. Then i am going to replace some of the whites with the blues. I hope my corals do okay under the whites.

[shark565]

I didn't wanted to create a new topic. Is there any way to conect two runing tanks. I want to conect my pico to the new tank and use it as a frag tank.

[shark565]

I think my power aupply died. It has a green ibdicator that is not lighting like it used to. I put it in a plastic food container because it is not waterproof. Can it overheated or there is another ploblem?