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| Planning for LED |
 Aug 24 2009, 03:13 PM
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#1
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 --With my cross-bow i shot the ALBATROSS Posts: 838 Joined: 23-October 03 From: Sweden Member No.: 5,215  |
Planning to build a LED for my new nano, had originally thought going to go the cheaper PC route, but lack of lamps here in Sweden stopped that. Have couple of questions that i hope someone can answer.
The aquarium is more or less a cube, about 11 inch each direction. The back of the tank has built in refugium, that will not be lit by the led lights as of now. Perhaps something in the future. The LEDs i was planning to use is the CREE-XRE Q5, white and royal blue. 1. Number of LEDs The heatsink i can get has the size of about 8 x 6 inch, i could fit 12 LEDs on that with a spacing of about 1 inch, is it to dense or is it ok? Or would it be ok less? 2. Power supply. I was planning to use 2 buckpucks and connect the blue and white to seperate drivers. How many volts and amps would i need in the Power supply? 3. Connection. Is it best to connect 6 in a series or 3 and 3 parallel? Is there any difference in the end result? Thanks -------------------- ><((((°>
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Aug 24 2009, 04:22 PM
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#2
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 LED Gawd  Posts: 9,888 Joined: 26-August 07 From: Shelby Twp. Michigan Member No.: 30,696 |
1. That should work, but a spacing of 2" would be a lot better.
2. 24v @2.2A or greater. 3. 6 in series. Connecting in parallel leads to potential trouble. Anyway, you would cut your current in half if you did two parallel strings of LEDs. -------------------- |
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Aug 24 2009, 05:15 PM
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#3
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--With my cross-bow i shot the ALBATROSS Posts: 838 Joined: 23-October 03 From: Sweden Member No.: 5,215 |
Perfect, thanks...
What about the distance from the edge of the heatsink? Any minimum there? 1 inch would be enough or can i make it smaller, so it will be more space between the LEDs. With 1 inch i have a spacing of 1.18 inch between the LEDs. -------------------- ><((((°>
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Aug 24 2009, 05:23 PM
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#4
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LED Gawd Posts: 9,888 Joined: 26-August 07 From: Shelby Twp. Michigan Member No.: 30,696 |
QUOTE (evilc66 @ Aug 24 2009, 04:22 PM)  1. That should work, but a spacing of 2" would be a lot better. -------------------- |
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Aug 24 2009, 05:28 PM
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#5
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--With my cross-bow i shot the ALBATROSS Posts: 838 Joined: 23-October 03 From: Sweden Member No.: 5,215 |
2" everywhere.. got it!
 Have to think about removing a couple of leds then i suppose, downsize it to 9, or find a bit bigger heatsink.Thank you again. -------------------- ><((((°>
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Aug 24 2009, 08:08 PM
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#6
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LED Gawd Posts: 9,888 Joined: 26-August 07 From: Shelby Twp. Michigan Member No.: 30,696 |
Why? A 12 LED array arranged in 4x3, with 2" spacing would only take up a 6"x4" area leaving you with an inch on each side with an 8"x6" heatsink.
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Aug 25 2009, 01:20 AM
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#7
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--With my cross-bow i shot the ALBATROSS Posts: 838 Joined: 23-October 03 From: Sweden Member No.: 5,215 |
Then i misunderstood you, i thought you meant 2" from edge to edge of the led-star, not center to center.
Sticking with my original plan then. -------------------- ><((((°>
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Aug 25 2009, 07:47 AM
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#8
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LED Gawd Posts: 9,888 Joined: 26-August 07 From: Shelby Twp. Michigan Member No.: 30,696 |
Right. 2" center to center.
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Nov 7 2009, 09:13 AM
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#9
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--With my cross-bow i shot the ALBATROSS Posts: 838 Joined: 23-October 03 From: Sweden Member No.: 5,215 |
A new question.. I guess it don't matter so much if i buy LED on Star or not. At led-tech.de they only have this for royal blue http://www.led-tech.de/en/High-Power-LEDs-...177_120_77.html Is there any difference between the star and this package, or is it just to use whatever?
Dimmable or non-dimmable driver? Led-tech has some nice cheap non-dimmable drivers for about third of the price of a dimmable driver from a local shop. Does it really matter? I know it's possible to control the light more carefully with a dimmable, but the light output will be quite balanced anyway right? with 6 white and 6 royal-blue? Led-Techs drivers: http://www.led-tech.de/en/LED-Controlling/...53_118_119.html http://www.led-tech.de/en/LED-Controlling/...53_118_119.html http://www.led-tech.de/en/LED-Controlling/...91_118_119.html This post has been edited by Swedereefer: Nov 7 2009, 09:28 AM -------------------- ><((((°>
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Nov 7 2009, 10:43 AM
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#10
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Nano Reefer Posts: 17 Joined: 28-February 08 Member No.: 34,915 |
QUOTE (evilc66 @ Aug 24 2009, 05:22 PM) 3. 6 in series. Connecting in parallel leads to potential trouble. Anyway, you would cut your current in half if you did two parallel strings of LEDs. Dun mind me asking, what are the potential trouble in parallel leads? JC |
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Nov 7 2009, 11:04 AM
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#11
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LED Gawd Posts: 9,888 Joined: 26-August 07 From: Shelby Twp. Michigan Member No.: 30,696 |
The problem comes from when an LED fails. If one fails open (typical failure mode), one string shuts down, and the other string now gets all the current (assuming 2 parallel strings). Not so bad if the total current is within the limits of the LEDs, but not good if you were running a driver with high current, and the divided current between the strings was at the limit for the LED.
There is also an issue when the LED fails closed (short). The string with the bad LED is still lit, but the forward voltage forced across each LED is now higher. The current may still be in check, but the LEDs can be damaged from excessive voltage. -------------------- |
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