How to control PC fans with a Pot?

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Hi all;

I've got 2 PC fans (12V dc running from a 500mA rated supply). Thing is,
whenever I try to use a pot to control their speed, the pot starts smoking.

This has just got to be possible, but everything I try just smokes the pot.

How can I control the fans with a 1/4 watt pot? do I use a transistor and
use the tranny to control the base current, thereby avoiding the power
dissipation issues?

Thanks

-Markus



Re: How to control PC fans with a Pot?



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really?

Re: How to control PC fans with a Pot?



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You're using the wrong method to control the pot.

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Use a pulse width modulation system. Jaycar sell a DC motor speed control
kit for about $24. It's an overkill (designed for motors up to 10A), but it
will do the job. The kit number is KC-5225. Or you could use a 555 timer
as a PWM, driving a transistor or a FET.

OR

Use a 3 position switch that switches the following to the fan.
1. 5V and 0V    - low
2. 12V and 5V     - medium (the fan sees 7V)
3. 12V and 0V    - high

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Re: How to control PC fans with a Pot?



"Markus Stone"
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 **  Use an LM317 adjustable regulator IC to vary the voltage.

http://www.hw.cz/data_ic/lm317.pdf



...........     Phil



Re: How to control PC fans with a Pot?


I found this very helpful..  http://www.cpemma.co.uk/index.html


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smoking.
pot.



Re: How to control PC fans with a Pot?


I can email you a simple circuit if you like
Mel


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and



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