dual color leds

[mollick2]

I'm curious as to how dual color leds work, what exactly is the deciding factor of what color it is at any givin moment and how you would control the color.

is it decided by the forward flow of mA or what?

I ask this because i'm trying to figure out how exactly i could hook them up to switches on my fanbus i am building.

Which brings me to another question, could i control the fans with a double pol switch and have a 12v and 5v line to run the fans(all rated 12v) have the 5v as a low power for idle times and 12v for when it was being used? or would this not work?

[Spawn-Inc]

first off welcome to the forums!

as far as the led are concerned there only 1 colour, i'm not sure how they get there colour but no matter the voltage (within certin limits) and there is only 1 way for the current to flow otherwise it won't work. bi or ever tri coloured led's basically have 2 or 3 led's in one head.

http://www.dansdata.com/images/caselight/led322.jpg

theres the anode and cathode. here is a really good picture to show you.

http://www.electronics2000.co.uk/data/images/LED.gif

with bi or tri leds theres more anode. you can see the two anode's in the picture below.

http://img.alibaba.com/photo/51195278/5mm_Bi_Color_LED_Lamp.jpg

its hard to see but there are 3 anodes in this one.

http://www.ledshoppe.com/Photo/Product%20photo/PICT0637.JPG

here is how you would hook it up, red is positive, and black is negative.

http://img504.imageshack.us/img504/6779/untitleded9.th.png (http://img504.imageshack.us/my.php?image=untitleded9.png)


I'm curious as to how dual color leds work, what exactly is the deciding factor of what color it is at any givin moment and how you would control the color.

so to answer your question it's basically 2 or 3 led mashed into one.

as for the second part i'm pretty sure you can. i made this picture as to go about hooking it up. so find a crappy/older fan that still works and test it out. i'm 90% sure it will work. the reason i'm not too sure is because i'm not clear if by double poll switch you mean a switch with on | off |on switch. if thats the case it would work.
the black wires are negative/ground, red is 12volts and positive, and yellow is 5volts positive.
http://img504.imageshack.us/img504/1828/fanfo1.th.png (http://img504.imageshack.us/my.php?image=fanfo1.png)

[.Maleficus.]

*Paint made LED + Battery pic*
Did you intentionally make that look like a penis?

[Spawn-Inc]

HAHA, oh man i didn't even see that and i can turn anything sick.

[xRyokenx]

Did you intentionally make that look like a penis?
Of course that's what's noticed first, lol. :rolleyes:

[.Maleficus.]

HAHA, oh man i didn't even see that and i can turn anything sick.
So it wasn't intentional? It didn't look a little weird when you made it? lol I'm just kidding man.


Of course that's what's noticed first, lol. :rolleyes:

:D You know you saw it too...

[Jim Beam]

I never thought of hooking the LED's up to my balls either

[mollick2]

thanks for your help, i was planning on using the dual color led's as a indicator so for the fan being on low or high, but i don't think it would be too simple.

[.Maleficus.]

thanks for your help, i was planning on using the dual color led's as a indicator so for the fan being on low or high, but i don't think it would be too simple.
I think you're probably right. While it might be possible, I think the color of the LED is pretty cut-and-dry, ie. it would be either red or blue, no in between so all it would really do is indicate -50% or +50%. You might be able to do it with a toggle switch, and have one side be connected to 5v and run the fan off that (low speed) and then the other side be 12v (high speed) and have the LED switch on either side, but then you would only get 2 speeds, and I'm not even sure how easy that would be.

[Spawn-Inc]

thanks for your help, i was planning on using the dual color led's as a indicator so for the fan being on low or high, but i don't think it would be too simple.

it wouldn't work on the same switch with the fan. you would need two switchs, one for the led and the other for the fan. i just tried making a paint picture of it and i couldn't make it work with out lighting up both leds (both poles on a bi colour) at the same time.

[mollick2]

thats what i thought, i think i'll forget the indicators then.

[Jim Beam]

you could just use a single color LED run a small circuit in parralel with the fan circuit. or you could get real fancy and use a micro controller. easy to programm and learn about here (http://www.parralax.com)

[Spawn-Inc]

you could just use a single color LED run a small circuit in parralel with the fan circuit. or you could get real fancy and use a micro controller. easy to programm and learn about here (http://www.parralax.com)

no that won't work, the led will always be on. but the micro controller might work.

[Jim Beam]

if you used a larger resistor so it was barely on at 5v and real bright at 12 v it might work then again I could be wrong

[xmastree]

Just to answer the unanswered question here, what makes them different colours...

It's simple really, they are made from different chemicals, which emit different coloured light.

[xmastree]

thanks for your help, i was planning on using the dual color led's as a indicator so for the fan being on low or high, but i don't think it would be too simple.
Something which hasn't been mentioned (unless I missed it) is two colour LEDs with only two wires. These are made from two chips, wired in inverse parallel. The colour is determined by which way round you connect them.

It wouldn't be too difficult to indicate your fan speed, but you would need some electronics to drive the LED.

[calumc]

if i under stand what you're trying to do properly (which i think i do)
i saw a guide on building a dual voltage fanbus using dual color leds as indicators but unfortunately i cant seem to find it. i did get this one using single color leds:
http://www.metku.net/index.html?path=mods/baybus/index_eng
and you'll just have to modify it to suit your needs.
i'm not sure what the correct name for the switches you'll need is but it would be the ones that stop in the middle so you can use that as off.
as for the leds you'll be doing it just as in the diagram but you'll be cannecting the other lead to the 5v lead:
http://img122.imageshack.us/img122/9039/schemasz1.jpg

i think thats right but someone please correct me if i'm wrong

[mollick2]

edit: nvm i get it, read that link through, makes since now.

i don't get your changes though

[calumc]

thats prob not right what i did but what i was trying to do was put one colour on the 12v and one on the 7v. i did see a guide for it but i cant find it

[Spawn-Inc]

if i under stand what you're trying to do properly (which i think i do)
i saw a guide on building a dual voltage fanbus using dual color leds as indicators but unfortunately i cant seem to find it. i did get this one using single color leds:
http://www.metku.net/index.html?path=mods/baybus/index_eng
and you'll just have to modify it to suit your needs.
i'm not sure what the correct name for the switches you'll need is but it would be the ones that stop in the middle so you can use that as off.
as for the leds you'll be doing it just as in the diagram but you'll be cannecting the other lead to the 5v lead:
http://img122.imageshack.us/img122/9039/schemasz1.jpg

i think thats right but someone please correct me if i'm wrong

that would work for 12v but not 5v. the 5v will never turn on the way its wired.

ok so i just talked to my dad and there is a switch that will do what you want. its called a Double Pull Double Throw (DPDT),on-off-on toggle switch

http://www.effectsconnection.com/oscommerce/images/dpdttoggle%202.jpg

so now that i know the switch exists you would wire it up like this.

http://img62.imageshack.us/img62/9426/workinghc2.th.png (http://img62.imageshack.us/my.php?image=workinghc2.png)

i used the 3 prong style LED from here (http://www.lsdiodes.com/shop/index.php?main_page=product_info&cPath=5&products_id=57), good place BTW, and used this LED calculator (http://led.linear1.org/1led.wiz) for the resistors. its hookup up for 5v red (less speed less cooling) and blue for 12v (faster speed better cooling) i'm not sure if this will work but here is a link (http://www.alliedelec.com/Search/SearchResults.asp?N=0&Ntt=DPDT+toggle+on-off-on&Ntk=Primary&i=0&sid=46A3EF803147617F) to a search from a online store that sells the switchs. make sure when you look for a switch if you go through with this project that you look for a DPDT, on-off-on switch not a on-none-on.

so to answer your question finally yes, you can do it and thats how!


EDIT: this won't work after all, i'm working to see if it can. ok so i think i have it yet again but i'm going to work on it tomorrow or rather later today.

[xmastree]

Quick and dirty drawing...

http://www.lotechdesigns.com/host/images/6064wiring.png

DPDT centre off switch. Up, and the 12V is switched to the fan +ve and also to the red anode. Down, and the 5V is switched to the fan +ve and the green anode.

The LED cathode and the fan negative both go to 0V.

[Spawn-Inc]

SPDT centre off switch. Up, and the 12V is switched to the fan +ve and also to the red anode. Down, and the 5V is switched to the fan +ve and the green anode.

The LED cathode and the fan negative both go to 0V.

i looked up a SPDT On-Off-On switch and theres only 3 terminals so how come you show 6?



ok so i fixed it up and am confident it works. i went through the wiring to check for problems this time and found none. the reason my other attempts failed was becuase i was trying to use 12v and 5v's to run the led like the fan. i realized i don't need to have the led at 12v like like the fan. now boths colours of the LED run at 5v while the fan runs both.

http://img124.imageshack.us/img124/6830/workingihopeiz6.th.png (http://img124.imageshack.us/my.php?image=workingihopeiz6.png)

[xmastree]

i looked up a SPDT On-Off-On switch and theres only 3 terminals so howcome you show 6?
Sorry, I meant DPDT. Post amended...