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Using Variable-Speed Device on Recycled Computer Cooling Fan for DIY Solder-Fume Extractor.

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ToddB73

Jan 1, 1970
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Greetings
! :D

I'm thinking of making a DIY fume-extractor for soldering electronic components to the circuit board. I like the idea of being able to vary the fan speed. This would allow me to set the speed for best draw of fumes into the carbon-activated filter chamber.

What are the primary electrical considerations to properly match a potentiometer [/QUOTE][/QUOTE][/QUOTE] to a small fan ?

Thanks in advance !

ToddB73
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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The primary electrical consideration is not to use a potentiometer, or at least not the way you're thinking.

What you want to do is create a variable duty cycle PWM driver. Depending on the fan, this signal is used to drive the fan directly (2 or 3 wire fans) or is passed to the 4th wire (for 4 wire fans).

These are generally a very simple circuit using a 555, a few other components and a transistor. You could probably find several designs by googling "PC PWM fan speed controller schematic".

Other methods involve changing the voltage passed to the fan (by means of a linear or switchmode regulator. These will not give as good control (or control over as wide a range of speeds) but may be sufficient.

Simply placing a resistor in series with the fan will reduce the speed, but may also prevent the fan from starting.
 
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