Is the "7 Volt Trick" dangerous?

[eyor]

I'm talknig about running fans at 7 volts by using the +5V for ground and the +12V for power. This would create 7V for your fan to run off of, thus quieting it.
Could this hurt the power supply in any way? I have heard people talk about noise on the line, or the fan shorting and hurting other components. Is there any REAL danger?
Thanks!

 

[JimMc]

Been doing it for a year with no ill effects.

 

[eyor]

Okay, thanks. Maybe I will try it out. Do I have to bother with the other wires, the black ones, or do I just solder the 12V and 5V to the fan's power and ground lines?

 

[eyor]

Does anyone else have comments?

 

[eyor]

Has anyone else done this?

 

[eyor]

I guess not...

 

[Xe0n]

never done it but i understand the theory of it, will be doing it soon when i build my baybus, i find myself too cheap to shell out the $70 for a digital doc when i can build my own with a baybus and a pc-workshop.net slurp

but anyways, ignore the black wires, the whole point is that you use the 5v wire instead of the black wire in order to achieve the 7v since voltage is the difference between the two wires

 

[Rebels7]

Instead of doing this, buy a couple of rheostats and build a variable baybus. I built one and have had it working for several months. Used plans found here Cliff's Fanbus

 

[Noriaki]

Voltage is a potential difference in (electical) [potential] energy

Standard practice in circuits is to use X Volts and Ground (0V) but there is absolutely nothing wrong with use X+A volts and A volts, for a difference of X volts (in this case X would be 7 and A would be 5)

You just wire Yellow (+12) and Red (+5) to the +12 and Ground on the fan, the blacks are ground (0V) so ignore them.

 

[jamarno]

It rarely fails, and I know of two commercial designs that did something similar:

1. Toshiba wide carriage dot matrix impact printer, 18V fan at 12V

2. ITT PC, 24V Panasonic fan at 12V

 

[eyor]

Cool, thanks for the replies. I will probably try this tommorrow.

 

[cockeyed]

I've been running my CPU and case fans on +7v using the method your describe. I've been doing this for about 4 years now without any problems. A word of caution is to make sure that the fan will start reliably at 7 volts; most will, but some will not. I usually test them at first by pressing on them to start/stop them. Right now, my front case fan and CPU fan (Golden Orb) are running on 7v. The temp difference is minor and the noise is dramatically reduced.

 

[Xe0n]

id be careful about doping it with a cpu fan, i mean i woundnt really mess with those wires at all for fear of it comming unsoldered or something considering i never shut down, even if ur mobo automatically shuts down when it overheats, its just not a risk id take, but its up to you

 

[eyor]

I am only going to try to do this with my three case fans. Also, I have 2 identical fans at the back of my case, would linking these two together in series cause them to run at 6V?

 

[Mikewarrior2]

IT isn't dangerous. I have most of my case fans on rheostat's right now, but before they were on a 12v/7V SPDT switch.



Mike

 

[Regalk]

"You just wire Yellow (+12) and Red (+5) to the +12 and Ground on the fan, the blacks are ground (0V) so ignore them".

Not too clear - Does this mean the red and the yellow goes to the +12 connector - Isn't that 17 volts?? Should it not be the +12 and -5 (is there a -5) that goes to the +12 connector. And what happens to the former yellow conector?? Can the electrical chaps explain. Thanks.

 

[S0me1X]

I did this with 4 fans, three 80mm and 1 92mm.
It worked just fine on two of the 80 mm fans (2 Antec fans) and the 92mm (also Antec)

but my Sunon 80mm fan refused to spin after the 7v trick. If I help it spin (by spinning it with my own fingers) then the Sunon will start to spin and continue spinning. But I can't open my case and manually start my fan every time I turn on my computer, so I revered my sunon back to 12v. An object in motion stays in motion..

 

[Xe0n]

<< You just wire Yellow (+12) and Red (+5) to the +12 and Ground on the fan, the blacks are ground (0V) so ignore them&quot;.

Not too clear - Does this mean the red and the yellow goes to the +12 connector - Isn't that 17 volts?? Should it not be the +12 and -5 (is there a -5) that goes to the +12 connector. And what happens to the former yellow conector?? Can the electrical chaps explain. Thanks.
>>



No, you use the Yellow as is, and the red as if it were the black, because of how voltage works as potential DIFFERENCE, 12-5=7. I often wonder if people that dont understand electricity should be doing this, i highly suggest a begenning electronics class, or a basic physics class should teach you the theories.

 

[Regalk]

&quot;No, you use the Yellow as is, and the red as if it were the black, because of how voltage works as potential DIFFERENCE, 12-5=7. I often wonder if people that dont understand electricity should be doing this, i highly suggest a begenning electronics class, or a basic physics class should teach you the theories&quot;.

Thanks. Remember there are those who choose to pursue different paths to those who pursue the sciences - I chose to pursue business. From the little I know of electrical stuff I can do basic stuff (incl building computers) and that is good enough. However when it comes down to specifics sometimes one has to be careful. So don't be a smarty pants there fellow.

 

[eyor]

I'll test this out with an old PS that I have. I think all of my fans are made by Antec.

 

[cpemma]

Rather than go right down to 7v I'd suggest a few diodes in the fan wiring. Each diode drops 0.6v, so 4 will drop the voltage to 9.4v. Still reduces noise a lot, fan less likely to stay off, more air flow.

I use cheap 50v 1A silicon diodes, make sure diode end bands in red wire point to fan, in black wire point away from fan.

Try the fan first on a 9v battery, check it starts, feel the noise.

 

[cockeyed]

Here is a little tip that I use. Instead of popping pins from connectors, I make a &quot;stubby&quot; connector; the fan connector on one end and the +5/+12 converter on the other end. It is then just a matter of adding this in between the fan and standard connector. This might save you some grief and prevent damage when trying to pop the pins, if you don't have the correct pin removal tools.

 

[eyor]

Holy §h|T that scared me! Whoa... did I hurt my power supply/anything else?
I took a fan to test with, cut the end thing off, and stuck the leads into the molex connector. Ta-da! I feal air on my hand and hear a quiet, low-pitched hum. So of course I proceed to remove the leads and... AHH! IT BURNS! Oh wait, no, that's just sparks. I must have crossed the 0V ground with the 5V wire! The power supply got mad and restarted, a dove in terror, and managed to push(kick?) the off button on the computer. After my heart began beating again, I turned the comp back on. Every little beep and pause scared me... is it stopping because of what I did? lol... Well, here I am now, things are running fine... or so it seems. What have I done?
A: The PSU anticipates things like that and filtered it out. Thus, I simply found a new way of rebooting.
or
B: Any second now the computer is going to explode, and I will forever have silicone shrapnel embedded in my face, not to mention a brand new pile of duron goop.

Which is it, A or B?

 

[eyor]

okay, I'm starting to calm down. I don't see any problems. is that connector fried now? I still have a different fan that passes through that spot, and it is working fine.

 

[RGN]

ROFLMAO!!!!!!!!!!!