Stir Plate Speed

[WaltG]

OK, so I'm home sick and bored so of course I started watching homebrew videos on youtube and decided to try to piece together a stir plate.

I had an old PC fan from a power supply that crapped out on me.

It's a 12V fan that runs 2300RPM.

Now the only power supply I had was from an old cell phone that's 4.75V.

Now ideally does that just scale it down to around 850 RPMs?

Also how is that speed for a stir plate? Can i avoid buying the potentiometer?

 

[thekraken]

I'm guessing that wont be enough to run the fan. You can get wall warts at good will for dirt cheap.

 

[Hoppity]

No EE here, but I can't imagine trying to run a stirplate without speed control. The magnet (stirbar) either won't start or will fly off without careful voltage control.

 

[thekraken]

I made one of these: http://www.pcbheaven.com/circuitpages/High_Frequency_PWM_Fan_Controller/

maybe overkill but it was just something to do one day