Eliteforum
National Hazard
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Magnetic Stirrer Impro
Just going through the scipics dir, and noticed this picture: 
Anyone know who's it is? And how it was constructed?
As far as I can see, I see some sort of 80mm PC fan, (I have plenty of those!) and a switch and a few resistors or something.
Anyone knows who's it is? So I can ask for some spec's n stuff?
Cheers!
All that glitters isn't gold.
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axehandle
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I used a PC 80x80mm fan once together with some glue and a sawed-off piece of plastic together with a microswitch to create a PWM for an electric
motor (DC). From the picture, I'd deduce that someone has glued a rod-shaped permanent magnet to the fan, drawing a plastic-covered rod magnet
stirring device along with it in the fluid. The extra circuitry is probably just a PWM speed control. All those fans are DC.
But I could be wrong, as usual.
[Edited on 2004-3-16 by axehandle]
My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35
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chemoleo
Biochemicus Energeticus
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Hmm, I just checked, the maximum speed setting on my commerical magnetic stirrer is 1000 rpm, which is way too high for anything but extremely tiny
magnets. Larger magnets (>1.5cm) just cant keep up with the motor.
For any normal applications (such as mixing liquid in a beaker), the commonly used setting is betw. 300-500 rpm.
Somehow I think PC fans run at a higher speed than 300-500 rpm. However, with a variable resistor, one could adjust the DC current (do those fans run
at 5 or 12 V?), and thus vary the speed. The power of the fan though may not be enough to move bigger magnets in viscuous liquids.
At conrad.de (or maplin) one can buy motors with all sorts of rpm specifications, they may be more suitable for this.
Still, I think just a variable resistor is probably enough - one doesnt need all the electronics, unless the downstream motor eats up a lot of power.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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axehandle
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Unless one wants to be environmentally friendly.... or is experimenting with PWM controlled from a computer, which is what I did. The fan was
controllable from about 2rps to full speed.
Btw: They all run on 12V DC.
[Edited on 2004-3-16 by axehandle]
My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35
\"Verbing nouns weirds the language!\"
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Mumbles
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I believe that belongs to Brainfever. I'd recongnise that countertop anywhere. It's in all his pics. Besides that I've seen the
picture on another board.
http://www.geocities.com/brainfevert/magstir.html That also helped when forming my hypothesis.
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BrAiNFeVeR
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I confess
It's mine allright.
(I'll tell my mom you like her kitchen  )
It's nothing special really, it just is what it looks like.
A small power source (the entire cirquit board is the PS), just enough to feed the fan, a variable resistor and a pc fan with 2 strong little magnets
attached to the top.
EDIT: it can be improved by a simple voltage divider based on a transistor, now it has a non-linear speed on the resistor, but I don't really
care ...
[Edited on 21-3-2004 by BrAiNFeVeR]
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