12v to 5V rails to give 7v for Fan

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Hi
Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
things to the power supply? I am doing it but I jusy wonder what is
happing in the PSU. Can this be doen with any PSU?

Cheers
Kevin

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

You are about to DESTROY the power supply, and probably your motherboard.
Where the h*ll did you get this bright idea?

--
DaveW



"Kevin K" <kevin_nzl88@hotmail.com> wrote in message
news:607636b9.0502112232.b09feef@posting.google.com...
> Hi
> Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
> things to the power supply? I am doing it but I jusy wonder what is
> happing in the PSU. Can this be doen with any PSU?
>
> Cheers
> Kevin

 

[Dee]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

DaveW wrote:

> You are about to DESTROY the power supply, and probably your motherboard.
> Where the h*ll did you get this bright idea?
>

Who knows where he got the idea from, but if he wants to blow up his
computer, that's his business, not ours! He's probably got more money
that he has brains anyway.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

"Kevin K" <kevin_nzl88@hotmail.com> wrote in message
news:607636b9.0502112232.b09feef@posting.google.com...
> Hi
> Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
> things to the power supply? I am doing it but I jusy wonder what is
> happing in the PSU. Can this be doen with any PSU?

I think this is what you want:
http://www.heatsink-guide.com/content.php?content=connector.shtml

It works fine if you don't have the parts to make a speed controller and
need to cut down the sound your fans make.

--
Michael Cecil
http://home.comcast.net/~macecil/

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

DaveW wrote:
> You are about to DESTROY the power supply, and probably your motherboard.
> Where the h*ll did you get this bright idea?
>

Oh, for heaven's sake. Connecting a fan from the PSU +12 to +5 for 7 volts
won't harm a blessed thing.

Where do YOU get these bright ideas?

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Sat, 12 Feb 2005 16:05:06 -0800, "DaveW" <none@zero.org>
wrote:

>You are about to DESTROY the power supply, and probably your motherboard.
>Where the h*ll did you get this bright idea?

Possibly hundreds of thousands of people that've been doing
it for years without incident? It's quite easy to find
reports, Howtos, etc, about doing it, but quite rare to
hear of any problems... offhand I don't recall of anyone
reporting a problem from doing it. I'm not suggesting this
makes it a good idea though, not with so many other
alternatives, or even an entirely different (slower) fan
costing less than $5, OR a faster 12V fan (slowed down by)
running from 5V.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <Q5OdnVpI_oozBJPfRVn-2A@comcast.com>, DaveW says...
> You are about to DESTROY the power supply, and probably your motherboard.
> Where the h*ll did you get this bright idea?
>
Stupid twat.

How is he going to destroy the PSU?


--
Conor

An imperfect plan executed violently is far superior to a perfect plan.
-- George Patton

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On 11 Feb 2005 22:32:54 -0800, kevin_nzl88@hotmail.com (Kevin K) put
finger to keyboard and composed:

>Hi
>Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
>things to the power supply? I am doing it but I jusy wonder what is
>happing in the PSU. Can this be doen with any PSU?
>
>Cheers
>Kevin

I realise this doesn't answer your question, but someone with a little
electronics experience may like to build this "efficient fan speed
controller" using parts from their junk box:
http://www.siliconchip.com.au/cms/A_103659/article.html

It can be constructed from an old mobile phone car charger plus an NTC
resistor and some minor support components. The controller senses the
case temperature and adjusts the fan speed accordingly.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

"DaveW" <none@zero.org> wrote in message
news:Q5OdnVpI_oozBJPfRVn-2A@comcast.com...
> You are about to DESTROY the power supply, and probably your motherboard.
> Where the h*ll did you get this bright idea?
>


http://www.silentpcreview.com/article6-page1.html

--
Derek

>
>
>
> "Kevin K" <kevin_nzl88@hotmail.com> wrote in message
> news:607636b9.0502112232.b09feef@posting.google.com...
>> Hi
>> Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
>> things to the power supply? I am doing it but I jusy wonder what is
>> happing in the PSU. Can this be doen with any PSU?
>>
>> Cheers
>> Kevin
>
>

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

>
>
> http://www.silentpcreview.com/article6-page1.html
>
quote from above link

"You probably know by now that the standard IDE power connector from
the power supply contains 2 voltage lines and a third which is derived
from their difference: 12V, 5V and 7V. Running 7V CAN sometimes be
potentially stressful for the PSU for technical reasons I won't go
into here. (It is usually quite safe for a low wattage fan or two, but
if you want to be perfectly safe, you may want to avoid the 7V tap.)"

that's what I needed know.

Anyway I an running my fan/s with a swtich between 5 and 12V and
dropped the 7V option.

cheers
Kevin

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On 11 Feb 2005 22:32:54 -0800, kevin_nzl88@hotmail.com (Kevin K) put
finger to keyboard and composed:

>Hi
>Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
>things to the power supply? I am doing it but I jusy wonder what is
>happing in the PSU. Can this be doen with any PSU?
>
>Cheers
>Kevin

What would happen to the fan's electronics if the +5V rail powered up
before the +12V rail? There would only be a split second during which
the fan would be subjected to reverse polarity, but could this be
harmful?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Franc Zabkar wrote:

> On 11 Feb 2005 22:32:54 -0800, kevin_nzl88@hotmail.com (Kevin K) put
> finger to keyboard and composed:
>
>
>>Hi
>>Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
>>things to the power supply? I am doing it but I jusy wonder what is
>>happing in the PSU. Can this be doen with any PSU?
>>
>>Cheers
>>Kevin
>
>
> What would happen to the fan's electronics if the +5V rail powered up
> before the +12V rail? There would only be a split second during which
> the fan would be subjected to reverse polarity, but could this be
> harmful?

That would be potentially a problem for anything connected to both, not
just a 'fan', and power rails reversing polarity with respect to each other
is a no-no.

> - Franc Zabkar

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <uma2119ofc92lrcfcd5db9uescav5laj8s@4ax.com>, Franc Zabkar
says...

> What would happen to the fan's electronics if the +5V rail powered up
> before the +12V rail?

Nothing. It is the same as not being connected on one wire.

> There would only be a split second during which
> the fan would be subjected to reverse polarity, but could this be
> harmful?

How would it be subjected to reverse polarity? And its a motor...it
doesn't give a rats arse what way round the polarity is unless its a
stepper motor which it isn't.


--
Conor

An imperfect plan executed violently is far superior to a perfect plan.
-- George Patton

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <11139bfdcckchc8@corp.supernews.com>, David Maynard says...

> That would be potentially a problem for anything connected to both, not
> just a 'fan', and power rails reversing polarity with respect to each other
> is a no-no.
>
What polarity reverse?


--
Conor

An imperfect plan executed violently is far superior to a perfect plan.
-- George Patton

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Conor wrote:

> In article <uma2119ofc92lrcfcd5db9uescav5laj8s@4ax.com>, Franc Zabkar
> says...
>
>
>>What would happen to the fan's electronics if the +5V rail powered up
>>before the +12V rail?
>
>
> Nothing. It is the same as not being connected on one wire.

No, it's not.


>>There would only be a split second during which
>>the fan would be subjected to reverse polarity, but could this be
>>harmful?
>
>
> How would it be subjected to reverse polarity?

Because 5 volts being higher than the 12 volt rail is opposite in polarity
across the fan that if it's less than the 12 volt rail.

> And its a motor...it
> doesn't give a rats arse what way round the polarity is unless its a
> stepper motor which it isn't.

Not so. It's an electronically driven brushless motor.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Conor wrote:
> In article <11139bfdcckchc8@corp.supernews.com>, David Maynard says...
>
>
>>That would be potentially a problem for anything connected to both, not
>>just a 'fan', and power rails reversing polarity with respect to each other
>>is a no-no.
>>
>
> What polarity reverse?
>
>

If 5 is 'higher' than the 12 volt then the polarity across the fan is
reversed since it should be LOWER than 12 volts.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <1113p6gd8rdpodc@corp.supernews.com>, David Maynard says...
> Conor wrote:
> > In article <11139bfdcckchc8@corp.supernews.com>, David Maynard says...
> >
> >
> >>That would be potentially a problem for anything connected to both, not
> >>just a 'fan', and power rails reversing polarity with respect to each other
> >>is a no-no.
> >>
> >
> > What polarity reverse?
> >
> >
>
> If 5 is 'higher' than the 12 volt then the polarity across the fan is
> reversed since it should be LOWER than 12 volts.
>
Except that there is nothing there so electrically its a non
connection.


--
Conor

An imperfect plan executed violently is far superior to a perfect plan.
-- George Patton

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <1113pb6820ajb04@corp.supernews.com>, David Maynard says...
> Conor wrote:
>
> > In article <uma2119ofc92lrcfcd5db9uescav5laj8s@4ax.com>, Franc Zabkar
> > says...
> >
> >
> >>What would happen to the fan's electronics if the +5V rail powered up
> >>before the +12V rail?
> >
> >
> > Nothing. It is the same as not being connected on one wire.
>
> No, it's not.
>
Unless it has a path to 0V it is.



--
Conor

An imperfect plan executed violently is far superior to a perfect plan.
-- George Patton

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Conor wrote:
> In article <1113p6gd8rdpodc@corp.supernews.com>, David Maynard says...
>
>>Conor wrote:
>>
>>>In article <11139bfdcckchc8@corp.supernews.com>, David Maynard says...
>>>
>>>
>>>
>>>>That would be potentially a problem for anything connected to both, not
>>>>just a 'fan', and power rails reversing polarity with respect to each other
>>>>is a no-no.
>>>>
>>>
>>>What polarity reverse?
>>>
>>>
>>
>>If 5 is 'higher' than the 12 volt then the polarity across the fan is
>>reversed since it should be LOWER than 12 volts.
>>
>
> Except that there is nothing there so electrically its a non
> connection.
>
>

Not so.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Conor wrote:

> In article <1113pb6820ajb04@corp.supernews.com>, David Maynard says...
>
>>Conor wrote:
>>
>>
>>>In article <uma2119ofc92lrcfcd5db9uescav5laj8s@4ax.com>, Franc Zabkar
>>>says...
>>>
>>>
>>>
>>>>What would happen to the fan's electronics if the +5V rail powered up
>>>>before the +12V rail?
>>>
>>>
>>>Nothing. It is the same as not being connected on one wire.
>>
>>No, it's not.
>>
>
> Unless it has a path to 0V it is.

It has the same kind of 'path to zero' as when the 12 volt rail is higher
than the 5 volt rail. It's simply reversed (if it happened).

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 15 Feb 2005 01:31:58 -0600, David Maynard <dNOTmayn@ev1.net>
put finger to keyboard and composed:

>Franc Zabkar wrote:
>
>> On 11 Feb 2005 22:32:54 -0800, kevin_nzl88@hotmail.com (Kevin K) put
>> finger to keyboard and composed:
>>
>>
>>>Hi
>>>Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
>>>things to the power supply? I am doing it but I jusy wonder what is
>>>happing in the PSU. Can this be doen with any PSU?
>>>
>>>Cheers
>>>Kevin
>>
>>
>> What would happen to the fan's electronics if the +5V rail powered up
>> before the +12V rail? There would only be a split second during which
>> the fan would be subjected to reverse polarity, but could this be
>> harmful?
>
>That would be potentially a problem for anything connected to both, not
>just a 'fan', and power rails reversing polarity with respect to each other
>is a no-no.

I'm not sure what you mean by "power rails reversing polarity with
respect to each other". I was merely thinking of the situation where
the +5V rail was at 4V, say, while the +12V rail was still only at 1V,
if it were possible. This would mean that the fan would see -3V for a
short time.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 15 Feb 2005 09:43:26 -0000, Conor <conor.turton@gmail.com> put
finger to keyboard and composed:

>In article <uma2119ofc92lrcfcd5db9uescav5laj8s@4ax.com>, Franc Zabkar
>says...
>
>> What would happen to the fan's electronics if the +5V rail powered up
>> before the +12V rail?
>
>Nothing. It is the same as not being connected on one wire.

Huh?

>> There would only be a split second during which
>> the fan would be subjected to reverse polarity, but could this be
>> harmful?
>
>How would it be subjected to reverse polarity? And its a motor...it
>doesn't give a rats arse what way round the polarity is unless its a
>stepper motor which it isn't.

It's a brushless DC motor with an electronic, Hall effect based
commutator. Do some research before shooting your mouth off. Better
still, take one apart.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Franc Zabkar wrote:

> On Tue, 15 Feb 2005 01:31:58 -0600, David Maynard <dNOTmayn@ev1.net>
> put finger to keyboard and composed:
>
>
>>Franc Zabkar wrote:
>>
>>
>>>On 11 Feb 2005 22:32:54 -0800, kevin_nzl88@hotmail.com (Kevin K) put
>>>finger to keyboard and composed:
>>>
>>>
>>>
>>>>Hi
>>>>Does connecting you fans to the 12+ and 5+ to give 7 volts do any bad
>>>>things to the power supply? I am doing it but I jusy wonder what is
>>>>happing in the PSU. Can this be doen with any PSU?
>>>>
>>>>Cheers
>>>>Kevin
>>>
>>>
>>>What would happen to the fan's electronics if the +5V rail powered up
>>>before the +12V rail? There would only be a split second during which
>>>the fan would be subjected to reverse polarity, but could this be
>>>harmful?
>>
>>That would be potentially a problem for anything connected to both, not
>>just a 'fan', and power rails reversing polarity with respect to each other
>>is a no-no.
>
>
> I'm not sure what you mean by "power rails reversing polarity with
> respect to each other". I was merely thinking of the situation where
> the +5V rail was at 4V, say, while the +12V rail was still only at 1V,
> if it were possible. This would mean that the fan would see -3V for a
> short time.

When it's 'right' the voltage differential is +7 and the scenario you
describe put MINUS 3 on it. Going from + to - is a polarity reversal in any
book, and a no-no.

+12 is always to be above +5. Otherwise you have a polarity reversal with
respect to each other.

>
>
> - Franc Zabkar

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 15 Feb 2005 21:12:28 +1100, Franc Zabkar
<fzabkar@optussnet.com.au> wrote:


>>> What would happen to the fan's electronics if the +5V rail powered up
>>> before the +12V rail? There would only be a split second during which
>>> the fan would be subjected to reverse polarity, but could this be
>>> harmful?
>>
>>That would be potentially a problem for anything connected to both, not
>>just a 'fan', and power rails reversing polarity with respect to each other
>>is a no-no.
>
>I'm not sure what you mean by "power rails reversing polarity with
>respect to each other". I was merely thinking of the situation where
>the +5V rail was at 4V, say, while the +12V rail was still only at 1V,
>if it were possible. This would mean that the fan would see -3V for a
>short time.


Interesting idea but couldn't we expect the 12V rail to be
coming up faster because of the amount of capacitance on 5V
in a PC?

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <d5i311p20dm3nohe55iefs6fd166l1320a@4ax.com>, Franc Zabkar
says...
> On Tue, 15 Feb 2005 09:43:26 -0000, Conor <conor.turton@gmail.com> put
> finger to keyboard and composed:
>
> >In article <uma2119ofc92lrcfcd5db9uescav5laj8s@4ax.com>, Franc Zabkar
> >says...
> >
> >> What would happen to the fan's electronics if the +5V rail powered up
> >> before the +12V rail?
> >
> >Nothing. It is the same as not being connected on one wire.
>
> Huh?
>
> >> There would only be a split second during which
> >> the fan would be subjected to reverse polarity, but could this be
> >> harmful?
> >
> >How would it be subjected to reverse polarity? And its a motor...it
> >doesn't give a rats arse what way round the polarity is unless its a
> >stepper motor which it isn't.
>
> It's a brushless DC motor with an electronic, Hall effect based
> commutator. Do some research before shooting your mouth off. Better
> still, take one apart.
>
You've not answered my question. How would it be subjected to reverse
polarity when it has +5V on one line and in effect N/C on the other?


--
Conor

An imperfect plan executed violently is far superior to a perfect plan.
-- George Patton