Being an inveterate tinkerer I decided to build my own magnetic stir plate using a 3" fan and a rare earth magnet. The fan used is a 24v motor, the power supply is 12v 1000mA. The magnet is a 1 x 1/8 x 1/8 rectangular magnet which sticks, by it's own power, to the fans' hub. The speed is controlled by a Radio Shack potentiometer. At its lowest setting its still pretty fast, it will create a top to bottom vortex, with a corresponding rare earth magnet, in a 1000ml flask within a couple of seconds of power on.
It worked perfectly through the trial stages. It spun a corresponding rare earth magnet fast as a tornado and steady as a rock, it does the same with a 1" square section teflon stir bar in an empty flask. If there is any liquid in the flask however the stir bar makes a few revolutions and then shoots to the side of the flask and vibrates, (this doesn't happen with a rare rare earth magnet). I think the problem is that the fan is spinning too fast but before I try to build a speed control circuit for it, I'd love to have an expert opinion. I tried powering it with a 9v 200mA power supply but got the same results.
Thanks for your help, Rich.
It worked perfectly through the trial stages. It spun a corresponding rare earth magnet fast as a tornado and steady as a rock, it does the same with a 1" square section teflon stir bar in an empty flask. If there is any liquid in the flask however the stir bar makes a few revolutions and then shoots to the side of the flask and vibrates, (this doesn't happen with a rare rare earth magnet). I think the problem is that the fan is spinning too fast but before I try to build a speed control circuit for it, I'd love to have an expert opinion. I tried powering it with a 9v 200mA power supply but got the same results.
Thanks for your help, Rich.