LED Lighting Parts Question - The Planted Tank Forum
 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old 01-21-2010, 12:10 PM Thread Starter
Algae Grower
 
breakaway's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2010
Location: Akld, NZ
Posts: 45
Question LED Lighting Parts Question

Hi,

I've got an Aqua One AR380. Its a 10Gal aquarium which is 18 inches tall. Currently lit by one fluorescent 11w of some sort. This isn't enough light to grow the plants I want.

So I'm going LED. I've got some electronics understanding, so I don't see wiring to be that big an issue.

I'm having some problems selecting parts though.

So far, I've got 8 x Cree XR-E Q5 LEDs for lighting.

I need help with:

1. LED Drivers (What do I use? I want to drive the Q5s at at least 700mA)

2. Power supply from wall -> LED Drivers?
700mA * 8 = 5.6A
(Driving Amps * Amount of LEDs = total current).

So,
5.6A * 12V = 67.2W
(Driving Amps * Driving Input Voltage = Power supply total wattage needed.)

Does this mean I can get an old 200w computer power supply and rig up the LED drivers to the 12V rail on the power supply?

Basically I need to make sure my maths is correct and I'm on the right track. Secondly, Where can I source the LED Drivers from? I've already got a supplier for the LEDs (dealextreme.com/details.dx/sku.2394).

Now I need a place to get 10 of the LED drivers (8 for production, 2 for testing in case I blow some or something :p)

If someone knows a place that sell these online, It'd be great if the store ship overseas as I'm in New Zealand.
breakaway is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 01-21-2010, 02:07 PM
Planted Member
 
PTrader: (3/100%)
Join Date: Mar 2008
Location: San Juan, PR - Phoenix, AZ
Posts: 275
Best place closest to you in Au and they are very helpful over the phone.
JDowns is offline  
post #3 of 10 (permalink) Old 01-21-2010, 05:19 PM
Planted Member
 
PTrader: (1/100%)
Join Date: Dec 2009
Location: Wyoming
Posts: 221
When I get home I can find the link to the DIY driver for LEDs. Using a power FET, controller, and a few resistors is all, you can make the driver for a few bucks compared to what they want for retail drivers.

For a power supply I just ordered a 200W adjustable laptop power supply, mostly because with those Cree LEDs you end up with a lot of wasted power driving them with 12V just because of how they multiply out. Also, the spare PSUs I have are all of questionable quality and life remaining.
For instance, with your 8 lights you would have to have 2 sets of 3 and 1 set of 2. Which would mean the driver for the 3 LEDs would have to drop about 1-2Vs, and the driver for the 2 LEDs would have to drop closer to 5-6Vs, which will require larger parts on your driver and less overall efficiency.

As an aside, I've got those exact same LEDs ordered from dealextreme.com. Its been about 2 months now and they still haven't been shipped. The flashlights I ordered at the same time are here though. I ordered 14ish of them and they have been listed as pending supply for a long time now, so I think they have some and thats why its not listed as out of stock, but not that many.
Erloas is offline  
 
post #4 of 10 (permalink) Old 01-21-2010, 06:56 PM
Planted Tank Guru
 
PTrader: (84/100%)
Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,012
My 2 cents worth: It is a mistake to assume that you should drive each LED separately with one driver. Much better is to put some in series, enough to get close to the power supply voltage output. Then put the groups that are in series, in a parallel circuit, increasing the current needed, until it is close to the power supply optimum output current. That keeps both the voltage and the current to minimum total values.

If they are all in series, the voltage can be high enough to making isolating them from the heat sink a problem. If they are all in parallel the total current can be high enough to require attention to the size wire being used and can be too much for the power supply. And, of course, using a driver for each individual LED greatly adds to the cost of the light fixture.

Today there are many options for driving LEDs. Look through the Ebay listings and you will soon decide that there are too many.

Hoppy
Hoppy is offline  
post #5 of 10 (permalink) Old 01-21-2010, 11:40 PM
Guest
 
PTrader: (5/100%)
Join Date: Feb 2006
Posts: 227
Find a calculator like this http://led.linear1.org/led.wiz if you want to use a voltage regulated psu. Using a huge psu will be wasteful. There's some secondary reason you want a resistor in line with one of this type power supply and I don't remember it. Voltage spikes? I don't remember. On the plus side, you can easily alter the drive current.

Places like meanwell and xitanium make constant current drivers.

I think your math is messed up. Example, 3.5vf*.7a = 2.45w 2.45w*8= 19.6w

I cancelled my order for emitters from DX. It was more than a month and a half. Now there's something newer and better. Q5's are so last year.
MoonFish is offline  
post #6 of 10 (permalink) Old 01-22-2010, 03:30 AM
Planted Tank Guru
 
PTrader: (84/100%)
Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,012
Quote:
Originally Posted by MoonFish View Post

I cancelled my order for emitters from DX. It was more than a month and a half. Now there's something newer and better. Q5's are so last year.
Ah, but "last year" stuff, be it cars or LEDs, are much cheaper as a rule. If the cost isn't a problem, I agree that going with the latest and best is a better idea. What is the latest and best?

Hoppy
Hoppy is offline  
post #7 of 10 (permalink) Old 01-22-2010, 04:01 AM
Planted Member
 
PTrader: (1/100%)
Join Date: Dec 2009
Location: Wyoming
Posts: 221
Here is the constant current source I'm going to be using


As for the Q5s... yeah they are a bit older but they are also a fair amount cheaper. They had the R2 bins available, but you are spending about 20-40% more for maybe 5-10% more light. Its not a big deal if you are building a small lighting system, but if you consider that you need probably 24-36ish for a decent sized tank they really start to add up.
Erloas is offline  
post #8 of 10 (permalink) Old 01-22-2010, 07:30 PM
Planted Tank Guru
 
PTrader: (84/100%)
Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,012
http://www.instructables.com/id/Circ...urrent-source/ is the constant current source I'm using. I found it the easiest to make, and easiest to design modifications to. Mine has been working since last Summer, with no problems. The only problem with this circuit is finding the voltage regulators, which are really "last year's" big thing, so most hobby supply places don't have them any more. RadioShack has the original LM317 regulators, but I wasn't able to find the improved models anywhere.

Hoppy
Hoppy is offline  
post #9 of 10 (permalink) Old 01-22-2010, 11:05 PM
Planted Member
 
PTrader: (1/100%)
Join Date: Dec 2009
Location: Wyoming
Posts: 221
I just ordered all the parts I needed from Digikey and Newark. I had looked at that design a fair amount too, I just decided not to use it because the higher drop out was very potentially going to cause me problems with the voltage supply I'm planning on using. I think it also ended up being a little bit more expensive.
Erloas is offline  
post #10 of 10 (permalink) Old 01-23-2010, 06:28 PM
Planted Member
 
PTrader: (0/0%)
Join Date: Feb 2007
Location: NW Oregon
Posts: 292
Quote:
Originally Posted by Hoppy View Post
The only problem with this circuit is finding the voltage regulators, which are really "last year's" big thing, so most hobby supply places don't have them any more. RadioShack has the original LM317 regulators, but I wasn't able to find the improved models anywhere.
My favorite supplier: http://www.digikey.com I got all the parts for my AutoWC Controller there. Good search function and interactive online catalog, and small orders are no problem. Shipping is from Minnesota so it's reasonably quick to most of the country.

http://www.mouser.com is also a good source.
PDX-PLT is offline  
Reply

Tags
led lighting ar380 nano

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome