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Need some physics help!

post #1 of 8
Thread Starter 
Ok, so heres the dilemma. Searching around I found looots of different answers as to how many fans/leds i can hook up to a single cable/connector etc.

So, I put it to you guys:

Can I hook up to one cable with two molex connectors:

1. molex connector: 3x 120mm fans via daisy chain
2. molex connector: 2x 140mm fans + the led connector from my case's front panel (NZXT Tempest EVO)

So, basically, one cable, 2 molex connectors, 3x 120mm, 2x 140, and 2 small led strips.

Fans:

120mm:

Current: .16A
Input: 1.92W

140mm:

Current: .24A
Input: 2.88W

PSU:


Edited by dejanribic - 12/23/10 at 3:58pm
post #2 of 8
I was expecting a physics problem (like something from uni/school). Fans use the molex connector's 12v line. Some PSUs have different cables on different rails others have them all on one rail. Anyhow I don't see any reason that you'd have a problem with that.
post #3 of 8
Thread Starter 
Quote:
Originally Posted by TFL Replica View Post
I was expecting a physics problem (like something from uni/school). Fans use the molex connector's 12v line. Some PSUs have different cables on different rails others have them all on one rail. Anyhow I don't see any reason that you'd have a problem with that.
It's all one cable. Is that all right as well? Whats the math behind it?
Edited by dejanribic - 12/23/10 at 1:51pm
post #4 of 8
It doesn't matter that it's one cable. I think it would take a whole lot more than 5 simple fans to cause problems for that PSU. Molex specs indicate the max amperage is 11A/pin, you'll never reach that with a handful of fans.
post #5 of 8
Thread Starter 
Fired it up. Works fine. I put 2 x 120mm and the LED on one connector, and 2 x 140mm and 1 x 120mm on the other. One cable. If something IS wrong, when will the symptoms manifest?
post #6 of 8
Quote:
Originally Posted by dejanribic View Post
Fired it up. Works fine. I put 2 x 120mm and the LED on one connector, and 2 x 140mm and 1 x 120mm on the other. One cable. If something IS wrong, when will the symptoms manifest?
PSU problems manifest themselves as stuttering in games (that didn't exist before), sudden rebooting or loss of power (sometimes with smoke/fire as a bonus).
post #7 of 8
You can put 7-15A of load on a wire without too much trouble (~60 120mm fans, ~40 140mm). If you are drawing too much power on a rail, the wiring/connectors will start to heat up, so if the wiring or connectors are above being warm, you are drawing too much power.

The main consideration with power supplies is overloading your rails, so never connect more that what the maximum rating is for a rail.
post #8 of 8
there really isnt any math behind it,
but there is a very basic mathematical concept in electrical engineering, that parallel resistance is actually less then just one resistance, because electricity has no mass you actually make more total power when you split it, but then would lose it if you tried to combine them...
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aeoiu-lys
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CPUMotherboardGraphicsRAM
1090t Thuban @4.0ghz 1.43v nb 1.5v @ 3000 ASUS M4A89TD Unlocked HIS 6950 Ripjaws Series 8GB 2000 @ 1874 9-9-9-24 
Hard DriveOptical DriveOSMonitor
Intel x25m 160gb LG dvd Windows 7 ultimate 64bit Dell 21.5" 1680x1050 
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Microsoft 2500 Thermaltake Black Widow 850w Raidmax Aeolus DeathAdder 
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