Go Back   Aquarium Advice - Aquarium Forum Community > General Aquarium Forums > DIY Projects
Click Here to Login

Join Aquarium Advice Today
Reply
 
Thread Tools Search this Thread Display Modes
Please support our sponsors and let them know you heard about them on AquariumAdvice.com
 
Old 06-28-2010, 01:29 PM   #21
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Quote:
Originally Posted by corrado33 View Post
I don't think it'd be a bad idea. I mean (going along the computer power supply idea here), computer PSUs are VERY well regulated. They're powering hundred dollar components in your computer right now. That's a bit more demanding than a few LEDs. I don't know, I'll look into it and let you know.

Wow that didn't take long. I think the "key" is using "series-parallel" arrays. Check out the PDF I found...

http://www.edn.com/contents/images/6615611.pdf

Oh... well.. apparently that PDF concludes that series parallel arrays are useless haha Good read nonetheless.
Ill have to look through that more later, seems interesting. So series is still the way to go.
__________________

__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 01:31 PM   #22
Aquarium Advice Freak
 
Join Date: Feb 2010
Posts: 478
Quote:
Originally Posted by Jimbo7 View Post
Ill have to look through that more later, seems interesting. So series is still the way to go.
It looks that way. However, for me with my little LED project, I don't need perfectly equalized LEDs, and I think it's easier for me to just use LEDs in parallel. (Besides, I don't have the ability to run them in series lol)
__________________

__________________
corrado33 is offline   Reply With Quote
Old 06-28-2010, 01:40 PM   #23
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Sorry for the hijack, but how can you not run them in series?
__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 01:51 PM   #24
Aquarium Advice Freak
 
Join Date: Feb 2010
Posts: 478
I just have the positive end of both LEDs connect to +V and the negative to the GND (anode cathode ect etc). Therefore they are parallel? It works for me. However, after reading this site, it seems that "parallel-series" arrays work OK. (Not the best, but I'm using 1 dollar LEDs, if one burns out, I'll replace it).

EDIT: The guy uses a resistor to "ballast" the LEDs in series. I don't know if that can be used as a verb, but he did.

EDIT 2: If I were to try to make a long term LED lighting solution, I'd definitely do them in series. However, I don't plan to use this tank much longer (more than a year or two), so I'm sure the LEDs will be fine. I'm really just building a proof of concept thing.
__________________
corrado33 is offline   Reply With Quote
Old 06-28-2010, 02:02 PM   #25
Aquarium Advice Addict
 
krap101's Avatar
 
Join Date: Feb 2004
Location: Roscoe, IL
Posts: 6,084
Send a message via AIM to krap101
Quote:
Originally Posted by Jimbo7 View Post
Sorry for the hijack, but how can you not run them in series?
When you run a series of leds, they are all strung together, like christmas lights, but when they're in parallel, then each led is individually connected to the power source. When you run leds in series, they split voltage, so on a 21v 800ma power supply, you can run 7 3v leds at 800ma. When you run them in parallel, you'll need to split amperage, so 3v power supply with 5.6A for 7 leds.

HTH

Oh, and you can also run them in series and parallel. Lets say you have a 1.6A 15V power supply. That means you can run 2 lines at 800ma and have 5 leds in each string. (15/5=3 and 1.6/.8=2)
__________________
~ Danny
krap101 is offline   Reply With Quote
Old 06-28-2010, 02:49 PM   #26
Aquarium Advice FINatic
 
Join Date: May 2009
Location: tallahassee, florida
Posts: 990
Hello,
I believe a switching supply is going to put out a constant (with some ripple) voltage no matter the load. If the load isnt sized well, this will cause a lot of power to be dissipated by the supply. So that means no using a 48v SMPS to run a 3v LED. It wont fry the led if the current is regulated, but the power supply and wires will get hot. At least, that is the trouble I had with my high power laser diodes (they would draw 50A) and SMPS.

Now for the diodes in parallel. BAD BAD BAD! Do not do this unless you have a driver for EACH diode. Diodes do NOT share current evenly. Series is much better. The entire string is controlled by one driver. This is how the pros drive $10,000 laser diodes as well. Series is the best way. Each diode will drop some of the SMPS voltage across it according to its particular parameters. Then, to keep current steady, the driver will not allow current to fluctuate.(If a good design).

Resistors are 100% fine is using a battery. A battery will not have a ripple, or be susceptible to changes in the line voltage.
Since we dont use batteries, we need something better than a resistor. Enter the wide world of constant current controllers. :p

Usually they work by sensing a voltage across a precision resistor and then compare this voltage to a preset voltage. Using ohms law, the driver is able to determine how much current is flowing. It then adjusts its output to the diodes accordingly. Depending on the quality of the design, this can be extremely accurate, or it can suck.

I have no idea how the meanwells work, but I imagine something similar.

Matt
__________________
mrg02d is offline   Reply With Quote
Old 06-28-2010, 02:55 PM   #27
Aquarium Advice FINatic
 
Join Date: May 2009
Location: tallahassee, florida
Posts: 990
Quote:
Originally Posted by krap101 View Post
Quick question, awhile ago I was thinking about doing one of these with a laptop power supply, and I was wondering.. if I use a switching power supply, and lets say there are a few extra volts/amps at the end of a string, do I still need a resistor there, or does the switching power supply make it unnecessary?
You could always put a dummy diode in series with the LED to disspate the extra power. This may be a good idea if the PSU isnt very large and thus not looking to dissipate much more than it has to. You could also put a resistor in series. That would also drop some voltage. Either way, something is getting hot.

At less than 1A draw, it wont be too bad. Id just let the PSU pick up the slack.
Matt
__________________
mrg02d is offline   Reply With Quote
Old 06-28-2010, 03:01 PM   #28
Aquarium Advice FINatic
 
Join Date: May 2009
Location: tallahassee, florida
Posts: 990
Quote:
Originally Posted by Jimbo7 View Post
I have a username for nano-reefs. If you post your question in entirety, i can repost it there.

Krap, thats a good question, its something i was wondering too. The link posted earlier in this, the guy uses 5 LEDs for a 24v PS. Im not sure if he added anything or not to the end.

Hmmm...Here goes a question:
Hello,
I am planning on using the Meanwell 30-27-D dimmable LED PSU to drive 5-6LEDs. Has anyone here any experience with these drivers? If so, would this one be suitable for 5-6LEDs? (Cree XR-E 3W leds).
Thank you!

Nanotuners confirmed they are indeed the 27V output ones. I may ask them if they would be suitable for 5-6LEDs.

Thanks!
Matt
__________________
mrg02d is offline   Reply With Quote
Old 06-28-2010, 03:04 PM   #29
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Quote:
Originally Posted by krap101 View Post
When you run a series of leds, they are all strung together, like christmas lights, but when they're in parallel, then each led is individually connected to the power source. When you run leds in series, they split voltage, so on a 21v 800ma power supply, you can run 7 3v leds at 800ma. When you run them in parallel, you'll need to split amperage, so 3v power supply with 5.6A for 7 leds.

HTH

Oh, and you can also run them in series and parallel. Lets say you have a 1.6A 15V power supply. That means you can run 2 lines at 800ma and have 5 leds in each string. (15/5=3 and 1.6/.8=2)
He stated that he was unable to run them in series, I was asking him why that was. I have a pretty firm grasp on how LEDs work already.
__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 03:14 PM   #30
Aquarium Advice Freak
 
Join Date: Feb 2010
Posts: 478
Quote:
Originally Posted by Jimbo7 View Post
He stated that he was unable to run them in series, I was asking him why that was. I have a pretty firm grasp on how LEDs work already.
I have a low voltage, high amperage power supply, that's why.

Well, technically I guess I could run them in series... I'm using a 12V 1A power supply, so it could go either way. Since the LEDs are only (maybe) a hundred milliamps, I'd either have to put some in parallel, or use a bunch of resistors which are going to get HOT.

EDIT: Remember, I'm not using really nice Cree LEDs, I'm using normal ones, which only draw (oh wow really low) 25 mA at 3.3V.

EDIT: Actually I just found an 18v 350 mA wall wort... hmmm... *rethinks design*
EDIT3: Ok I like the 12V power supply better. The fans are 12 V, and I don't want to have to regulate twice...
Sorry for thread jacking
__________________

__________________
corrado33 is offline   Reply With Quote
Reply

Tags
2.5 gallon, led, led lighting, light, lighting, pico, tan

Please support our sponsors and let them know you heard about them on AquariumAdvice.com

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not 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 Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LED lighting? snowdrop7 General Hardware/Equipment Discussion 11 06-03-2010 10:35 AM
5.5 gallon pico log, AquaStud's dorm room pico AquaStud Saltwater & Reef - Getting Started 2 04-09-2009 10:26 AM
LED Full Tank Lighting Jakers88 General Hardware/Equipment Discussion 6 07-12-2008 08:08 PM
New affordable Fish Tank Reef LED lighting....... lifereefer General Hardware/Equipment Discussion 9 04-22-2008 04:03 PM
LED Lighting clowninround General Hardware/Equipment Discussion 3 09-16-2007 01:18 PM







» Photo Contest Winners








Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -4. The time now is 09:39 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.