Electronics > Beginners
how to pull 12v from PSU on PC?
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Monkeh:

--- Quote from: ddmeltzer8 on October 01, 2019, 02:13:08 am ---After reading the latest comments and thinking about it,it is quite clear that this forum is not at all what i thought it was!
If people can can just say things that will result in damaged/broken devices without anyone even being bothered by it,im not comfortable taking advice from anyone here.
I hope this will be cleaned up...

--- End quote ---

You didn't specify the type of fan - there are types which can be reversed and types which cannot. As we're not mind readers, we may make different assumptions.

No matter who gives the advice, do not follow blindly, and realise you're responsible for what you do, not us.
Monkeh:

--- Quote from: ddmeltzer8 on October 01, 2019, 02:24:38 am ---So,some PC fans r brushed?That would actually be quite useful.U have any specific fans in mind?
--- End quote ---

Not that I've ever noticed, but you never specified what type of fan. Typical PC fans are brushless, but you still haven't specified what sort of fan you're actually using, so assumptions are being made.


--- Quote ---The thing is that when a poster has several thousands of posts on THIS forum i thought that actually meant something...but if u want this forum just to be perceived as any other random internet forum,im starting to see why no one thinks this is even an issue.

--- End quote ---

It means they've made a lot of posts. I don't know if he was trolling you or just made an assumption. This is not any other random forum.
gnif:

--- Quote from: ddmeltzer8 on October 01, 2019, 01:58:15 am ---So MarkF was lying?
Thanks.

--- End quote ---

No, he was not, you did not specify that it was a computer fan, he may not have much experience with computers and as such assumed you were using a brushed DC fan, which can be reversed by switching the polarity.


--- Quote from: ddmeltzer8 on October 01, 2019, 01:58:50 am ---Monkeh says u r lying!R u?

--- End quote ---

--- Quote from: ddmeltzer8 on October 01, 2019, 02:02:01 am ---Thanks.
Is this trolling by MarkF something that is tolerated here?Im quite shocked that no one seems to be offended by this.

--- End quote ---

--- Quote from: ddmeltzer8 on October 01, 2019, 02:05:18 am ---And u should stop telling others what they should prefer!Idiot.

--- End quote ---

--- Quote from: ddmeltzer8 on October 01, 2019, 02:08:18 am ---Thanks but im not talking about CPU,but directly from the PSU.(6 pin)

--- End quote ---

--- Quote from: ddmeltzer8 on October 01, 2019, 02:13:08 am ---After reading the latest comments and thinking about it,it is quite clear that this forum is not at all what i thought it was!
If people can can just say things that will result in damaged/broken devices without anyone even being bothered by it,im not comfortable taking advice from anyone here.
I hope this will be cleaned up...

--- End quote ---

This barrage of messages was over a 14 minute period, this is NOT live chat, you have to give people a chance to respond to your questions. Nobody was offended at @MarkF, but I am sure many, including myself, are offended by your impatience and name-calling. This forum is full of patient and mature people very willing to teach and IMO is one of the most friendly places on the internet. Don't let my admin status fool you, this is not my forum, I am simply a forum member what helps Dave with server management, which I do out of my own pocket and time because this community gives so much to people like me that want to learn.

Also on the actual topic, a brushed fan (ie reversible) would be a bad thing to use inside your PC if that's your intention. Not only will noise be a concern due to no speed limiting, but electrical noise would be a concern also, the arcing of the brushes on the commutator as it switches coils emit EMI, which could interfere with the operation of your computer. The DC motor would also introduce noise in the forum of high voltage spikes as the magnetic field of each coil collapses unless you add some protection (usually a snubber diode), and as the brushes wear (they literally grind down) fine conductive carbon/copper particles would be thrown into your PC case and could cause shorts over time. Also, a brushed motor wears out far faster and uses more energy.

There is a reason why we use brushless fans in computers.

If you really want a reversible brushless fan I suggest you look at building or obtaining a brushless motor controller and replacing the electronics of a brushless fan with your custom controller, though I believe that this is a bit beyond your abilities at this time based on this and your other threads. Otherwise, it might just be easier to mount two fans back to back and only power up the one you want based on direction of airflow.
Ian.M:
Also, a typical PC PSU may well be able to deliver 30A at +12V.  Make a mistake with your connections, and if you didn't include an inline fuse, odds are you'll burn something.  If what you burn is the PSU output cable you tapped into, it may melt through the insulation on a 5V or 3.3V wire where the bundle comes out of the PSU, and that can dump 12V onto the 3.3V or 5V supply, which will probably fry your motherboard.  Worst case, it could fry your motherboard, CPU, RAM, and all add-in cards and drives.  If you are really unlucky, the dead parts can then kill whatever you try to test them in!

Therefore PC modding should *NOT* be attempted by anyone who doesn't have plenty of patience, and a good understanding of electrical theory and safe wiring practices.  Also, don't attempt to mod your main PC unless you've got a full backup + a spare that can get you back on the internet!
JustMeHere:

--- Quote from: ddmeltzer8 on October 01, 2019, 02:05:18 am ---And u should stop telling others what they should prefer!Idiot.

--- End quote ---

I was hoping you could do a little research on your own, but I will give you the answer:

The advantage of using the chassis fan header on the motherboard is that system can monitor the fan for health (3-pin header) and control the speed (4-pin header).   Some motherboards will control the fan speed via the 3-pin header.
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