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, 03:25 PM   #31
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Ah, thats what i overlooked. It didn't actually register when i read your post.
__________________

__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 03:48 PM   #32
Aquarium Advice FINatic
 
Join Date: May 2009
Location: tallahassee, florida
Posts: 990
Quote:
Originally Posted by corrado33 View Post
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
Why would you need a lot of resistors? What are you trying to do with resistors, limit current? Current draw doesnt matter, just the LED voltage drop at the current you plan to draw.

Okay, so you have a 12v 1A PSU...How many leds are you trying to run?

Dont worry about threadjacking, I do it all the time!
Matt
__________________

__________________
mrg02d is offline   Reply With Quote
Old 06-28-2010, 03:55 PM   #33
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Correct me if im wrong, but he is planning on running these little guys in parallel, so he would need resistors to drop the excess amperage off. You have a 1000mA power supply and 5-6 25mA leds, so he would need to disperse the extra 850mA at the end along with the excess voltage? correct?

I dont know much about parallel.
__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 04:06 PM   #34
Aquarium Advice FINatic
 
Join Date: May 2009
Location: tallahassee, florida
Posts: 990
Quote:
Originally Posted by Jimbo7 View Post
Correct me if im wrong, but he is planning on running these little guys in parallel, so he would need resistors to drop the excess amperage off. You have a 1000mA power supply and 5-6 25mA leds, so he would need to disperse the extra 850mA at the end along with the excess voltage? correct?

I dont know much about parallel.
Amperage isnt something that exists like voltage. Voltage across a load causes amperage. The extra voltage would have to be dealt with, as it will drop across the circuit evenly and causes current to flow through loads. 1000mA is just the rating of the PSU of what it can deliver if required. Actual current draw will depend on the load.

Also, size the PSU right accordingly to the overall voltage drop of the circuit. If you use a 24v supply and 24v worth of LEDS, you get 0A of current. You need a potential difference in voltages for current to flow. Also keep in mind that connecting wires will drop voltage across them as they have a resistance (although small). So 7 LEDs will not run on a 24v supply.

Matt
__________________
mrg02d is offline   Reply With Quote
Old 06-28-2010, 04:28 PM   #35
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Alright, I'm not sure if you are talking about series or parallel anymore.
In series, amps are constant, and volts drop.
In parallel amps drop and volts are constant.

In parallel, if i understand correctly, amps are caused by the load, so from the beginning of the string to the end, you should drop all amperage, but you still have full voltage load at the end. Are you talking about using resistors to drop that end voltage?

I understand how series work fine, i've been over that with a bunch of people, im just trying to educate myself with you guys talking about parallel.
__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 04:56 PM   #36
Aquarium Advice FINatic
 
Join Date: May 2009
Location: tallahassee, florida
Posts: 990
Quote:
Originally Posted by Jimbo7 View Post
Alright, I'm not sure if you are talking about series or parallel anymore.
In series, amps are constant, and volts drop.
In parallel amps drop and volts are constant.

In parallel, if i understand correctly, amps are caused by the load, so from the beginning of the string to the end, you should drop all amperage, but you still have full voltage load at the end. Are you talking about using resistors to drop that end voltage?

I understand how series work fine, i've been over that with a bunch of people, im just trying to educate myself with you guys talking about parallel.
Parallel shouldn't be used IMO. Series is the best way to do this. If its good enough for Coherent and Spectra Physics in their $10,000 diodes, then its good enough for us.

In parallel, each load can/will draw different amounts of current. No two diodes are 100% the same, there will be slight differences and that translates into more or less current draw and imperfect load sharing.

Parallel configurations are commonly used with resistive loads.

Current is a function of voltage and load impedence. It does not exist by itself.

In parallel circuits, the same voltage gets applied to each load. The load then draws current based on its impedence. So, the voltage is the same but the current draw from the supply adds up from all the loads drawing their own current from the line.


Matt
__________________
mrg02d is offline   Reply With Quote
Old 06-28-2010, 05:14 PM   #37
Aquarium Advice Freak
 
Join Date: Feb 2010
Posts: 478
Quote:
Originally Posted by Jimbo7 View Post
Correct me if im wrong, but he is planning on running these little guys in parallel, so he would need resistors to drop the excess amperage off. You have a 1000mA power supply and 5-6 25mA leds, so he would need to disperse the extra 850mA at the end along with the excess voltage? correct?

I dont know much about parallel.
Like mrg said, in parallel the amperage is dependent on the circuit, however LEDs naturally draw enough current to blow themselves up. (Well, most do, there are some with built in resistors and all that fun stuff.) So I was saying I'd need resistors on each LED to keep it from blowing itself up.

No, that isn't what I meant originally, but it's what I'm pretending I meant. And it's true nonetheless. I think I'm going to go with LEDs in series, then in parallel, like an array. So I'll have (making stuff up here), 3 strings of 5 LEDs, the 5 LEDs will be in series, and the 3 stings will be in parallel.
__________________
corrado33 is offline   Reply With Quote
Old 06-28-2010, 05:23 PM   #38
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Quote:
Originally Posted by mrg02d View Post
Parallel shouldn't be used IMO. Series is the best way to do this. If its good enough for Coherent and Spectra Physics in their $10,000 diodes, then its good enough for us.

In parallel, each load can/will draw different amounts of current. No two diodes are 100% the same, there will be slight differences and that translates into more or less current draw and imperfect load sharing.

Parallel configurations are commonly used with resistive loads.

Current is a function of voltage and load impedence. It does not exist by itself.

In parallel circuits, the same voltage gets applied to each load. The load then draws current based on its impedence. So, the voltage is the same but the current draw from the supply adds up from all the loads drawing their own current from the line.


Matt
That makes sense, I know series is the way to go but I was just trying to understand what corr just explained above about his plans for a parallel circuit.. I like to soak up any and all information i can
__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 is offline   Reply With Quote
Old 06-28-2010, 06:24 PM   #39
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
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.
Oh lol, for a moment there I felt smart
__________________
~ Danny
krap101 is offline   Reply With Quote
Old 06-28-2010, 06:32 PM   #40
AA Team Emeritus
 
Jimbo7's Avatar
 
Join Date: Feb 2008
Location: Minneapolis, MN
Posts: 1,996
Haha, np. It's really good information and explained well. With all the activity these LED threads have been getting, i'm sure it was a big help to someone.
__________________

__________________
Links to old builds:
12DX LED Build
Frag Tank (Fixed Link)
Dorm Pico Tank
Jimbo7 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 08:26 AM.


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