Creating a fan control via a Potentiometer

AI Thread Summary
A user attempted to create a fan control using a 100-ohm potentiometer but initially connected it incorrectly to the yellow wire, which is for the tachometer output. The fan remained at full speed without any change when adjusting the potentiometer. Clarifications about wire color coding revealed that the red wire typically carries +12V, while yellow is for RPM monitoring. After advice to connect the potentiometer to the red wire instead, the user successfully achieved variable fan speed control. The discussion highlights the importance of understanding wiring and circuit connections in electronics projects.
CyborgPatrick
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Hi, I wanted to create my own computer fan control and bought a 100ohm potentiometer.

I have hooked the pot as shown in the picture except that it is in the yellow wire (+12V) and not the red one (+5V) , black is ground.

control.jpg


The fan will start at full speed and doesn't change one bit if I turn the knob. Any ideas why the pot doesn't work?
 
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Just for clarification, does the attached circuit accurately represent what you have done? i.e. you're essentially trying to create a voltage divider with only one resistance (assuming the load resistance is << the potentiometer).
 

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If this is a standard computer fan, the red wire is probably 12V (or sometimes 5V), black is ground, and yellow is the tachometer OUTPUT from the fan. HOWEVER, the colours are not standardized across all manufacturers (though the functions will be--the fan label usually tells you which is which).

Can you hook up a multimeter to the leads you've connected, and see if the resistance is actually changing when you turn it?

EDIT: What I meant to say with the colour coding is that you've left it somewhat ambiguous as to which red and which yellow wires you're using: the fan's or the power supply's.
 
The POT is currently attached to the yellow wire as Zryn's picture shows. And the other wires are unchanged. My PSU has a color label saying yellow (+12V) black (ground), another black (ground) and a red (+5V) .
But I think you are right about the color coding of the 3-pin fan wires, red is +12V, yellow is monitor (RPM) and black is ground.

I will try putting the POT on the red one and see if it fixes it. Seeing the color label on the PSU just confused me a bit + I'm not that good with electronics.

Added 6.12 PM
Works like a charm, thanks for the help!
 
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