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24v from a 12v PSU!

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mysterfix

Member
Joined
Jan 11, 2005
Location
Holly, MI
Hey guys I just rigged up a fortron 300w that I got off the forums to run my 24v Denki's. I found out thru some reaserch that if you wire up your ground wire from your fans to the -12v rail and run the hot wire to the +12v rail, you get 24v! You have to use the 20 pin connector to get your power from but if you have an old PSU and you want to have a dedicated power supply for your fans and such it works great. I've only been testing since last night but it looks good so far.

The PSU isn't even blowing out warm air, it feels cool like there's not even a load on it. This setup takes a major load off of my X-connect. I still need to do a few more test to see if it's pheasable to use the molex connectors to power other hardware. I'll let ya know in a few days how it's going.
 
mysterfix said:
Hey guys I just rigged up a fortron 300w that I got off the forums to run my 24v Denki's. I found out thru some reaserch that if you wire up your ground wire from your fans to the -12v rail and run the hot wire to the +12v rail, you get 24v! You have to use the 20 pin connector to get your power from but if you have an old PSU and you want to have a dedicated power supply for your fans and such it works great. I've only been testing since last night but it looks good so far.

The PSU isn't even blowing out warm air, it feels cool like there's not even a load on it. This setup takes a major load off of my X-connect. I still need to do a few more test to see if it's pheasable to use the molex connectors to power other hardware. I'll let ya know in a few days how it's going.


yup, same theory with the 7v fan mod (12v - 5v = 7v: 12v - (-12v) = 24v). What you could always do to make ALL connections 24v/17v instead of 5v, is open the PSU, and run all COM wires from every connector but the ATX and mobo connectors to a -12 wire. Then all black wires on molexes and the likes are -12 instead of 0v. so if you wire a fan so the hot is running on the yellow wire, and then black-black, its gonna be 24v, and if you wire a fan to red/black, it'll be 17v.
 
there's only 1 thing to be careful of here- the -12v line is only meant to take a very small amount of amperage, so yes a fan or 2 will be ok, but anything more like, a peltier would blow it out.
 
Aphex_Tom_9 said:
there's only 1 thing to be careful of here- the -12v line is only meant to take a very small amount of amperage, so yes a fan or 2 will be ok, but anything more like, a peltier would blow it out.


I vote for 50a -12v rails in the ATX 3.0 Spec

:D
 
Aphex_Tom_9 said:
there's only 1 thing to be careful of here- the -12v line is only meant to take a very small amount of amperage, so yes a fan or 2 will be ok, but anything more like, a peltier would blow it out.
Yeah I thought about that but I should be ok. My Denki's are only drawing 0.21 amps at max voltage and my -12v rail is rated at 0.8 amps so I still have a little left for something else.
 
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