Overclock.net › Forums › Components › Power Supplies › A question that's semi-related to power supplies... (At least it's about supplying power)
New Posts  All Forums:Forum Nav:

A question that's semi-related to power supplies... (At least it's about supplying power)

post #1 of 4
Thread Starter 
For a school project, I need to build something that uses electricity so I thought about building some kind of fan controller.

What I thought I could do was use some potentiometers but I couldn't find any that could handle roughly 10W and were affordable (most were over 10$ or had to be bought in increments of 1000 and I don't want that many channels rolleyes.gif).

My second idea was to use a 4-pin peripheral connector (aka molex) and a PWM cable and then split the 12V source from the molex connector to 4-6 PWM fan connectors and split the PWM signal to the connectors. This way, I can supply more power than a single motherboard header can supply. Problem is, most of my fans don't use PWM connectors...

My last idea, and that's my question too is the following: Could I use a 3-pin connector with voltage control from the motherboard to control the fans BUT use a secondary source of power (a molex connector) to provide additional power and bypass the motherboard header limitation. (I'm pretty sure that's impossible but who knows...)

Also, do you know if there's a place that I forgot which sells some fairly cheap potentiometers that can handle at least 10w? Thanks smile.gif
My Gaming Rig
(16 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i5 2500K @ 4,5GHz - 1.296 volts MSI P67A-GD55 Asus Strix Geforce GTX 970 4GB Mushkin Enhanced Silverline Stiletto 2x4GB 1333... 
Hard DriveHard DriveHard DriveHard Drive
Seagate Barracuda 7200.12 1TB Seagate Barracuda 7200.12 500GB Toshiba HDKPC08 3TB Samsung 840 Evo 120GB 
CoolingOSMonitorKeyboard
Corsair Hydro Series H60 Windows 8.1 Professional x64 BenQ G2420HD 24" 1920x1080 IBM Model M2 French Canadian Layout '93 
PowerCaseMouseMouse Pad
Mushkin Enhanced Joule 1000W Modular Antec DF-35 (Modded) Razer Deathadder 3500 DPI Mionix Sargas 900 
  hide details  
Reply
My Gaming Rig
(16 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i5 2500K @ 4,5GHz - 1.296 volts MSI P67A-GD55 Asus Strix Geforce GTX 970 4GB Mushkin Enhanced Silverline Stiletto 2x4GB 1333... 
Hard DriveHard DriveHard DriveHard Drive
Seagate Barracuda 7200.12 1TB Seagate Barracuda 7200.12 500GB Toshiba HDKPC08 3TB Samsung 840 Evo 120GB 
CoolingOSMonitorKeyboard
Corsair Hydro Series H60 Windows 8.1 Professional x64 BenQ G2420HD 24" 1920x1080 IBM Model M2 French Canadian Layout '93 
PowerCaseMouseMouse Pad
Mushkin Enhanced Joule 1000W Modular Antec DF-35 (Modded) Razer Deathadder 3500 DPI Mionix Sargas 900 
  hide details  
Reply
post #2 of 4
Why would you need the potentiometer to handle that much power? The potentiometer isn't going directly in series with a fan, I hope? (and if so, the impedance would need to be really really low)

#3 can also work. You just need to get some kind of voltage buffer. The voltage from the motherboard is the input to the buffer, it can get power from molex, and the output of the buffer is connected to the fan. You can use a specialized unity-gain stable op amp buffer or some power BJT (or multiple) as long as it is specified for enough power, and of course some resistors too. Buffers might be relatively expensive though.
post #3 of 4
Thread Starter 
Yeah I realised a potentiometer wasn't gonna work :/ I figured out I'd need a rheostat instead so would this one work? : http://www.ebay.ca/itm/25W-30-Ohm-Glazed-Ceramic-Variable-Resistor-Rheostat-/280852717125?pt=LH_DefaultDomain_0&hash=item4164205e45#ht_1833wt_1396

Also, when you're talking about a voltage buffer, is that what you're talking about? : http://en.wikipedia.org/wiki/Buffer_amplifier#Voltage_buffer

If I do that, could I also use a potentiometer/rheostat that's rated for a much lower power rating to set the voltage to the buffer and then the buffer would set that voltage to the circuit that goes to the fan? Basically:

240
My Gaming Rig
(16 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i5 2500K @ 4,5GHz - 1.296 volts MSI P67A-GD55 Asus Strix Geforce GTX 970 4GB Mushkin Enhanced Silverline Stiletto 2x4GB 1333... 
Hard DriveHard DriveHard DriveHard Drive
Seagate Barracuda 7200.12 1TB Seagate Barracuda 7200.12 500GB Toshiba HDKPC08 3TB Samsung 840 Evo 120GB 
CoolingOSMonitorKeyboard
Corsair Hydro Series H60 Windows 8.1 Professional x64 BenQ G2420HD 24" 1920x1080 IBM Model M2 French Canadian Layout '93 
PowerCaseMouseMouse Pad
Mushkin Enhanced Joule 1000W Modular Antec DF-35 (Modded) Razer Deathadder 3500 DPI Mionix Sargas 900 
  hide details  
Reply
My Gaming Rig
(16 items)
 
  
CPUMotherboardGraphicsRAM
Intel Core i5 2500K @ 4,5GHz - 1.296 volts MSI P67A-GD55 Asus Strix Geforce GTX 970 4GB Mushkin Enhanced Silverline Stiletto 2x4GB 1333... 
Hard DriveHard DriveHard DriveHard Drive
Seagate Barracuda 7200.12 1TB Seagate Barracuda 7200.12 500GB Toshiba HDKPC08 3TB Samsung 840 Evo 120GB 
CoolingOSMonitorKeyboard
Corsair Hydro Series H60 Windows 8.1 Professional x64 BenQ G2420HD 24" 1920x1080 IBM Model M2 French Canadian Layout '93 
PowerCaseMouseMouse Pad
Mushkin Enhanced Joule 1000W Modular Antec DF-35 (Modded) Razer Deathadder 3500 DPI Mionix Sargas 900 
  hide details  
Reply
post #4 of 4
A rheostat is just a type of potentiometer, the most common type. Or actually I'm not quite sure; usually I hear the terms used interchangeably, though maybe rheostat usually refers to a 2-terminal device? Anyway, you can always just not use the third terminal of a three terminal device.

If you want it in series with the fan...if the impedance is that low, I guess it should work, depending on the fan used.


As for the voltage buffer, yes and yes. That diagram looks right. Pretty much the potentiometer rotation is selecting what voltage (what fraction out of 12V input) gets sent to the voltage buffer; since the top of the potentiometer is connected to +12V and the bottom to ground, you're just getting a simple voltage divider.
Edited by mikeaj - 4/20/12 at 9:18pm
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Power Supplies
Overclock.net › Forums › Components › Power Supplies › A question that's semi-related to power supplies... (At least it's about supplying power)