got lost in reading on making a 5/0/12v switch thingy

[vedge_boy]

I want to make a 12 Volt High, 5 Volt Low, Switch tingy. I read on http://www.fanbus.com/ and I understood how to connect everyting except for the black ground wire. On the molex connector, it has 2 black wire. One for the 12v and the other one for the 5v. the pic on the site is very clear except of the ground wire. Where do I plug the ground? the one beside the 5v or the 12v?

 

[YMAN]

If you look in the pic you will see thay the
ground you are mixed up with is parallel with
the red wire. Thus I believe that you should
connect it to the 5v ground, or the ground wire
closest to the red wire on the molex.


--------------------
-------------------- <--- Attach the Ground to this black wire in the molex.
--------------------
--------------------

However in reality it should not make much difference.
If you are in a totle bind just attach the ground to a metal
part of the case! Instant Ground!

Hope This Helps

 

[Ichelo351]

ok, it really does not matter cause... if you open up your ps, you would see all the ground lines going to this big lump of sodier, soooo they are both the same. so it doesn't matter which you hook it to, which ever is easier, or you could even do both! hehe

hope this helps some!

 

[Über~PhLuBB]

ok, it really does not matter cause... if you open up your ps, you would see all the ground lines going to this big lump of sodier, soooo they are both the same. so it doesn't matter which you hook it to, which ever is easier, or you could even do both! hehe

hope this helps some!

Just so you don't go on blind faith from one suggestion, I second what he said. Either one, it doesn't matter.

 

[vedge_boy]

Thanks a lot, I now understand that It doesn't matter. I always thought that one was specific to handle 12v and the other one to handle 5v. Now I just found out that it is all the same! But why does my temp monitoring program monitors the -12v line and the -5v line since it is all the same?. If I put 4 fans with the switchs I make, should I plug 2 with the ground near the yellow one and 2 other one near the red one to equilibrate both of my -12v line and -5v line or should I plug all of them where the negative is higher or it just dosen't matter?

 

[Über~PhLuBB]

Thanks a lot, I now understand that It doesn't matter. I always thought that one was specific to handle 12v and the other one to handle 5v. Now I just found out that it is all the same! But why does my temp monitoring program monitors the -12v line and the -5v line since it is all the same?. If I put 4 fans with the switchs I make, should I plug 2 with the ground near the yellow one and 2 other one near the red one to equilibrate both of my -12v line and -5v line or should I plug all of them where the negative is higher or it just dosen't matter?

You should notice that the "-12" and "-5" lines actually read 0v, not -5 or -12. I read an article awhile back by a guy who said he ran 24 volt fans between +12v and -12v, but I dont understand how that's possible concidering that -12 is zero volts.

If you MUST run 4 fans off of one 4-pin molex, then yes, do 2 fans per ground to help distribute the load over two wires instead of just one. Less resistance means better voltage (although it'll barely be noticeable).

 

[Ichelo351]

the -5v and -12v are totally seperate from that, the -5v and -12v only run to the mobo, and they are used for some components, you can run a fan at 24v by going from the +12 to the -12, or 17v by going from the +12v to the -5v, but the lines are really not rated for that kindof current, so it is possible to blow a ps out by doing that. thats weird that your are showing 0v, because it is in the atx spec to have them, and you ps should have ratings for those lines. i dunno why yours isn't showing it, mine does...

and yes, if you are running so many fans off of one connector, spreading it out might be a good thing to do, but like he said, you probably woln't notice much of a difference...

 

[Maximus Nickus]

Heres a very clear picture for you.

Top: Molex
Left: Switch (3 pin variety)
Right: Fan!


Maximus Nickus

 

[YMAN]

Yes indeed those lined are used for some
older floppy drives and the mobo. In no
way say they are the same voltage, they
are different. If you want proof, a voltmeter
is a good start.

See that blue wire on the ATX molex? Make that
a ground and make the yellow wire the + You will
have a little more than 12v...

--------------------------

vedge_boy,
I think it might a good idea to run the fan thing
in a 7v/12v setup insted of a 5v/12v setup. I am
not against the 5v/12v setup; but computer fans
cannot properly function at that voltage witch will
shorten the life of the fans. 7v will greatly reduce
noise while keeping the fan happier.

If you want 5v short the 5+ and 12+ together.
(red and yellow) This will cause the lines to cancel
each other out making 7v. Use this line that you
will creat as the + and have the ground connected
to the -12 or black wire next to the yellow in the molex.

 

[vedge_boy]

YMAN,
I don't want to do a 7/0/12v switch because I read in another post somewhere in this forum and it is bad to put 7v because the psu isn't made to handle the 7v. the 5 volt line isn't made for that and I don't want to mess up my psu. Even if people have done the 7v trick, I don't want to do that. I tried plugging some fans at 5v and it works. I will change for a 120mm fan later on and if the 5v won't work, I will probably put a reostat instead. Doing the 7v trick isn't one of my options I want to do.

 

[YMAN]

Yes, I fully understand and yes, it IS bad on
you power supply. But if your power supply is
of decent quality you will be fine.

------

Or... You can have it run the fans at 12v / 24v
like me!

 

[LiquidConfusion]

I like the 12V/7V idea myself and it can be done with a resister or pot in line somewhere with the 12V line as for the PSU it shouldnt care about dropping the voltage after its down line. Afterall the PSU creates the 5V lines from the original 12V its basic AC/DC theory
the downfall of this would be using another 12V line..

 

[LiquidConfusion]

Yes, I fully understand and yes, it IS bad on
you power supply. But if your power supply is
of decent quality you will be fine.

How would you do it that it would be bad for your power supply? Humor me plz...Im curious

 

[YMAN]

you drop the voltage by mixing the +5 volt
and the +12 volt line together to form +7v. You
get +7 volts because the +5 & +12 lines try
hard to dominate each other; the result is they
cancel each other out forming +7 volts!

The down side is that it stresses the regulators
and rectrifier diodes, witch can reduce the life
of the power supply. I however would not worry
to much unless you have some type of generic.

 

[LiquidConfusion]

ok thanks guess thats one way of doing it Im just a circuit minded person ran about 4 possiblities through my head and none of them was that... The stress would be caused by the combining of the current then not the voltage Just ignore that PM i sent you then