DIY LEDs - The write-up

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Right Guys, something for you ...

Stu your LEDs are on its way.......one with 10k and one with 25k

My 15000k

15000K.jpg


My 20000k

20000K.jpg


My 25000k
25000K.jpg


Now all these are 3 watt LEDs

Enjoy
 
Last edited:
Soundwave,

I believe he sent them to me because I was the 'unbeliever'.

PM me your address & once I get a look at them I will forward them to you.

Stu
 
I hope its earlier than that! ;-)

Soundwave,

How come you drove your blues at 700ma and your whites at 1000ma... why not both at 1000ma?

Wouldn't that make the blues brighter, and more preferrable?

thx
 
Soundwave and all,

Thanks to all the great info and discussion around this project, I have decided to go and order the parts necessary to do my own. I'm going to build this into my Coralife Aqualight Pro fixture.

I'm going to take out the 150W MH from the middle , and see if I can mount the LED arrays and heatsinks on the sections on either side.

I've ordered all Cool White LEDs, since I can continue to use the PC actinic bulbs.

I've also ordered the dimmable buckpucks, and I'm going to see if I can't get this all to work with DA's ALC module for the Reef Keeper Elite.

I'll take lots of pictures and document the build, so I can post a thread when the time comes.

Thanks again!
 
For everyone that is going to attempt one of these builds.

Try to NOT drive the LEDs at their full rated current.

You WILL:

1 - Severely shorten their life.
2 - NEED to have a nearly perfect heat sink or they burn out
3 - Even if they live 1/2 of the rated 50,000 hours, you will have major degradation of the Lumen output.
4 - Greatly increase the chance of burning one out & lose ( or destroy ) a whole string, depending on your setup

So for the 3W LEDs that are rated at 1000mA ( 1 Amp ), I would suggest not driving them at more than 750mA ( 0.75 Amp ).


Also - just dont try to drive any strings in parallel with others.
It is possible, but the electronics/fuses required to protect the LEDs are not worth the cost of more drivers.

Remember - people complain about the cost of one buckpuck, but consider the cost of a whole string of LEDs WHEN you burn them all out.

Stu
 
Stu thanks for posting that reminder.

Most of my LEDs are 1000ma rated and I'm using 700ma pucks.

But I was planning to mix a Cyan LED in one of the arrays, its rated at 700ma max.

Could I just position it at the end of a series and put a resister before it to step it down?
 
wow! a ton of useful info here... soundwave, thank you soooo much for posting this! i plan on using just a quarter of your setup in addition to my elos e-lite (shown below). since the e-lite doesn't have seperate power chords or a controller to independently control the blues and whites, i want to add 6 royal blue XR-E Crees for an actinic sunrise/sunset effect.

now, i need some criticism on how i plan on doing this...
elos says that the fixture acts as the heat sink for the 18 stock CREE leds and current owners have no complaints with heat (it is a solid block of aluminum). so... what i want to do is thermal epoxy 6 star PCB boards to the e-lite fixture

the fixture sits about 4 inches from the water surface. would this be a major issue having the led boards exposed that close to the water surface? do you think it would be best to use optics (just so the leds are covered)? the tank it self is only 17"x17" so having 6 LEDs spread out, i may be able to avoid "dead spots".

if you guys have any other thoughts to incorporate some blue leds with the fixture i have already, it would be much appreciated!

thanks in advanced,
philip
underthee-lite.jpg
 
stu or soundwave.......

ok, i'm about to order the 350mA dimable w/ pot buckpuck for my 1watt blue moonlights from ledsupply.com & i just happened to glance at the auctions where i bought my LEDs on ebay & saw something i need clarification on.....

HERE are the 3watt white LEDs i purchased. i know they are not true luxeons but i am just using them to add "shimmer" to the tank & not for coral growth, so that doesn't concern me.

what peaked my curiosity is the part in the specs where it lists the
DC Forward Current (IF): Typ 650mA ....the buckpuck i purchased is 700mA.

there will be (5) of them running on a 20V-1A Wall Wart

while i'm buying the dimable buckpuck for the 1 watt LEDs, should i buy a 500mA buckpuck to use on the 3 watt instead of the 700mA one i have ??

thanks again :)
James
 
james3370,

"Typ 650mA ....the buckpuck i purchased is 700mA"

As I mentioned in the PM:

"The ebay page says typical current is 650mA.
Without the datasheet, I cant say if 700mA is OK."

So it WOULD be better to get a lower current buckpuck, but you can hook it up long enough to see what the REAL current is & see if you are OK. ( quickly with a DMM ).

The Pucks appear to be driving a little lower than their rating according to the discussion way early on of Soundwaves implementation.

Stu
 
<a href=showthread.php?s=&postid=14725521#post14725521 target=_blank>Originally posted</a> by stugray
So it WOULD be better to get a lower current buckpuck, but you can hook it up long enough to see what the REAL current is & see if you are OK. ( quickly with a DMM ).
Click to expand...

yeah, that's what i was thinking. since they are just for a shimmer effect, i'd rather drive them a bit less on a 500mA puck than take the risk of using the 700mA puck & end up frying all 5 of them

anbody need a 350mA & 700mA puck?? LOL
 
<a href=showthread.php?s=&postid=14724710#post14724710 target=_blank>Originally posted</a> by ReefEnabler
Stu thanks for posting that reminder.

Most of my LEDs are 1000ma rated and I'm using 700ma pucks.

But I was planning to mix a Cyan LED in one of the arrays, its rated at 700ma max.

Could I just position it at the end of a series and put a resister before it to step it down?
Click to expand...

Negative, negative, negative!!

The same current runs thru all of the elements in a series chain.


But! You can achieve what you want by shunting the LED of your choice with a resistor so some of the current runs around your LED. Since properly sized and mounted resistors don't fail this is a safe 'paralleling'.

Tell me the expected VF for the LED you want toned down and the current you will be running and I can tell you what resistor you'll want. (Better would be the actual VF, of the actual LED, at the actual current.)
 
Hi ReefEnabler,

If you want to reduce the current thru a particular LED in a chain you put an appropriate resistor in parallel with the LED of interest.

To do this you need to figure out what the resistance needs to be and the resistor's required power rating.

If we take a cyan triple chip as an example:
Looking at the data sheet we see the forward voltage is 6.84V at 700mA.

Now if you only want to run 550mA thru this puppy you need to shunt 150mA around it somehow, (700-550 = 150). Hence the shunt resistor.

Using the voltage: 6.84V / 150mA = 45.6 ohms.

So if there is a 45.6ohm resistor in parallel with the LED it will be robbing 150mA of the 700mA that is being provided. This means there is 150mA less to run thru the LED and it will get only 550mA thru it.

There is a caveat here which is why I said the actual measured values would be better - but we will persevere. If the LED's forward voltage is 6.84V at 700mA it will be less than this at 550mA. How much less? It could be a lot less.. Especially if, out of the box, your LED is already a low VF value out of the batch it was made in.

What does this really mean? Well it means that after the math above the the actual shunt current will end up being something a little less than what's calculated. This means you will reduce the current thru your LED a little less than expected. But since this is all a bit seat-of-the-pants, less than 700mA, is already going to help the LED's life dramatically.

Ok, now on to the power calculation.

It's easy:
Power(watts) = V x V / Resistance.

P = 6.84V x 6.84V / 45.6 ohms
P = 1 watt

Prudent design requires you use a resistor that is at least two times this and better would be 3 times. Two times would probably still lift your finger prints off instantly. I would probably go 3X

So you want a 3 watt or larger resistor. Now that we know what size we are hunting we can find one. No one makes a 45.6 ohm resistor so you pick a lesser value due the 'caveat'.

43 ohms is a standard value.

I would use one of these two they are both 5W which is much more common and will run cooler yet:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=43W-5-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=805F40RE-ND

Hook it up in parallel with the aforementioned LED.
 
Does anyone know how difficult it is to wire a Potentiometer to a buck puck?

Can you wire one Pot to multiple buckpucks to do the dimming?
For example, buy a buckpuck with Pot and wire them together with the ones that don't come with the Pot.

I ask because it costs $4 more for a buckpuck with Potentiometer, and depending on how many buckpuck I buy, I can save some money here. ( I lose the ability to dim each buckpuck, but I'm okay with that as long as there are some cost savings)

Thanks.
 
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